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  • Other Sources  (530)
  • SOLAR PHYSICS  (288)
  • ELECTRONICS AND ELECTRICAL ENGINEERING  (242)
  • 2005-2009
  • 1990-1994  (530)
  • 1990  (530)
  • 1
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    Control of a GaAs monolithic Ka-band phase shifter using a high-speed optical interconnect (1990)
    In:  Other Sources
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    Publication Date: 2011-12-09
    Description: The use of a high-speed optical interconnect in the control of a Ka-band GaAs monolithic phase shifter is described. A 16-b serial control signal was used to modulate the output of a laser transmitter, and the transmitted optical signal was detected and demultiplexed into 16 parallel electrical outputs using a high-speed hybrid GaAs optoelectronic integrated circuit. Four of the parallel output lines were interfaced to the 4-b phase shifter, and high-speed, optically controlled switching of the phase shifter was observed at clock frequencies to 30 MHz using an interferometric technique.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Microwave Theory and Techniques (ISSN 0018-9480); 38; 686-688
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  • 2
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    Sunspot seismology theory (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Physical mechanisms proposed to explain the absorption of significant p-mode wave power by sunspots are reviewed, and their viability in view of the current knowledge of the scattering process is discussed. It is concluded that there is no satisfactory theoretical model for the absorption of p-modes by sunspots available at present. It is argued that the resonance absorption model is able to obtain the large absorption coefficients observed for nonaxisymmetric perturbations. For axisymmetric perturbations, departures from perfect cylindrical symmetry or the inclusion of a slight twist in the sunspot flux tube may be able to resolve the problem with the absorption of m = 0 wave modes. Other dissipative models, which do not incorporate the background gradient effects inherent in the resonance absorption mechanism, require inconveniently large dissipation coefficients within the sunspot.
    Keywords: SOLAR PHYSICS
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  • 3
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    Global configuration of a magnetic cloud (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A magnetic cloud associated with a 2N flare on January 1, 1978 was observed by IMP-8, Helios A, Helios B, and Voyager 2. The variation of the magnetic field observed at each spacecraft is represented to good approximation by Lundquist's solution for a cylindrically symmetric force-free magnetic field with constant alpha. A least-squares fit of Lundquist's solution to the data from each spacecraft gives the local orientation of the axis of the magnetic cloud. The times of the estimated boundaries of the magnetic cloud at each spacecraft, together with the speeds of the boundaries and the spacecraft position, give the positions of the boundaries at a given time. From these results the magnetic cloud is determined to resemble a flux rope whose minor radius is approximately 0.15 AU at 1 AU, and whose radius of curvature at 1 AU is approximately 1/3 AU.
    Keywords: SOLAR PHYSICS
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  • 4
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    Resonant absorption of p-modes by sunspots (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Explanations for the observed p-mode absorption in sunspots are examined. It is demonstrated that any dissipative process like radiative, viscous, or resistive dissipation leads to the resonant absorption of acoustic waves incident on the sunspot tube, and that the resultant heating rate can be shown to be consistent with the observed absorption of the p-mode power impinging on an isolated inhomogeneously structured sunspot.
    Keywords: SOLAR PHYSICS
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  • 5
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    The Ulysses mission in the high latitude heliosphere (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Ulysses, a joint ESA/NASA mission launched in October 1990, will be the first to explore the high latitude heliosphere. Launch will be from the Shuttle and a Jupiter gravity assist will be used to send the spacecraft first over the southern solar pole approximately three and one half years after launch and then over the northern solar pole one year later. Instruments will be carried to study the solar wind, the heliospheric magnetic field, energetic solar particles, galactic cosmic rays, solar X-rays, cosmic gamma rays, cosmic dust and interstellar neutral helium. The radio signals used to track and transmit spacecraft data will be used also to sound the corona and to search for gravitational waves.
    Keywords: SOLAR PHYSICS
    Type: In: Observatories in earth orbit and beyond (A93-23401 07-89); p. 307-313.
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  • 6
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    SOHO - An observatory to study the solar interior and the solar atmosphere (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Solar and Heliospheric Observatory (SOHO) is described. The two main objectives of SOHO are to improve understanding of solar coronal phenomena and to study solar structure and interior dynamics from its core to the photosphere. The primary goals of the coronal and solar wind studies are to understand the coronal heating mechanism and its expansion into the solar wind. These goals will be achieved both by remote sensing of the solar atmosphere with high resolution spectrometers and telescopes and by in situ measurement of the composition and energy of the resulting solar wind and the energetic particles that propagate through it. The structure and interior dynamics are to be studied by helioseismological methods and the measurement of solar irradiance variations. The SOHO spacecraft will be three-axis stabilized and located in a halo orbit around the L1 Lagrangian point (approximately 1 percent of the distance from the Earth to the Sun). It is currently scheduled for launch in July 1995.
    Keywords: SOLAR PHYSICS
    Type: In: Observatories in earth orbit and beyond (A93-23401 07-89); p. 277-284.
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  • 7
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    Solar accelerated particles - Comparisons of abundances and energy spectra from particle and gamma-ray observations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Gamma-ray observations of the April 27, 1981 flare have been used to derive elemental abundances of both the ambient gas and the accelerated particle which interact with this gas to produce gamma rays. The results show that the abundances of the accelerated particles which produce the gamma rays are much more consistent with first-class particle abundances than with large proton-flare abundances. Observed bremsstrahlung spectral from 16 flares are compared with calculated bremsstrahlung spectra. It is concluded that the electrons observed in interplanetary space and the electrons responsible for gamma-ray production cannot be drawn from the same accelerated particle population without the former being affected by reacceleration or energy-dependent escape.
    Keywords: SOLAR PHYSICS
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  • 8
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    Space applications for high temperature superconductivity - Brief review (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An overview is presented of materials and devices based on high-temperature superconductivity (HTS) that could have useful space-oriented applications. Of specific interest are applications of HTS technologies to mm and microwave systems, spaceborne and planet-surface sensors, and to magnetic subsystems for robotic, rescue, and docking maneuvers. HTS technologies can be used in optoelectronics, magnetic-field detectors, antennae, transmission/delay lines, and launch/payload coils.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: ; : Artificial intelli
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  • 9
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    dc modulation noise in thin film magnetic recording disk media (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A study of dc modulation noise as a function of magnetic layer thickness has been conducted for plated longitudinal low-noise Co-alloy disk media with a range of 900 to 1100 Oe. The noise, produced by the application of a reverse longitudinal dc field to a uniformly magnetized disk, supplies data regarding the uniformity of the disk. A spectrum analyzer measures the noise by means of electronic detection, and noise spectra and autocorrelation functions calculated with a model are compared to the experimental results. The model correlates with experimental data to more than 0.99. The maximum distance between effective transitions diminishes from 2.8 microns to 1 micron when the thickness of the magnetic layer is increased from 25 nm to 60 nm. The maximum average transition amplitude is found to be independent of thickness, and is bounded by 0.001 of the saturation magnetization.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 10
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    Solar radiation on Mars (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. Presented here is a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.
    Keywords: SOLAR PHYSICS
    Type: Solar Energy (ISSN 0038-092X); 45; 6, 19; 353-363
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  • 11
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    A high-efficiency ferruleless coupled-cavity traveling-wave tube with phase-adjusted taper (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The design and performance of the first traveling-wave tube (TWT) to be built with a phase-adjusted taper (PAT) is discussed. By adjusting the phase of the electron bunch with respect to the RF wave for strong electron bunch formation at the beginning of the taper and strong power conversion at the end, the PAT achieves a high efficiency of power conversion from the electron beam to the RF wave. A PAT incorporated into the output section of a baseline 29-30 GHz ferruleless coupled-cavity TWT experimentally increased the peak RF power from 420 to 1000 W and the peak RF interaction efficiency from 9.6 to 22.6 percent.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Electron Devices (ISSN 0018-9383); 37; 2638-264
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  • 12
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    The 155-day solar period in the sixteenth century and later (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent interest in short solar periods has been stimulated by the discovery of a peak period of about 150-160 days in very energetic solar flares and hard X-ray flares. Auroral data are used here as a proxy for solar activity to show the presence of the peak in data from 1570 to 1573 and in some other time periods. The data are also used to show the absence or lack of prominence of this peak at other times in the nineteenth and early twentieth centuries.
    Keywords: SOLAR PHYSICS
    Type: Nature (ISSN 0028-0836); 347; 365-367
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  • 13
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    An estimate of the maximum speed of the solar wind, 1938-1989 (1990)
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    Publication Date: 2011-08-19
    Description: In an effort to estimate the highest flow velocity that the solar wind has exhibited at earth during the past 50 years, geomagnetic storms that occurred from 1938 to 1989 were surveyed, and the storms that were preceded by a major proton flare were selected. For each identified flare-storm pair, the average speed ('transit speed') of the associated interplanetary shock from the interval between the flare onset and the sudden commencement of the geomagnetic storm was calculated. In each case, the maximum solar wind flow speed was inferred from an empirical relationship (derived for a sample of recent events) between the shock transit speed and the peak flow velocity of the associated transient stream, obtaining a distribution of maximum solar wind speeds, which presumably corresponds to a sample of the most energetic events of this 50-yr period. Results show no evidence for bulk flow velocities greater than the about 2000 km/sec value deduced by Zastenker et al. (1978) and Grunwaldt (1975) for the August 4, 1972 event.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 17103-17
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  • 14
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    Where two frontiers meet (1990)
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    Publication Date: 2011-08-19
    Description: Current research projects conducted at the JPL Center for Space Microelectronics Technology are briefly reviewed. These include the development of a new miniature tunneling Goday cell that can be made into arrays. This tunneling IR detector is sensitive to radiation through the infrared and is particularly suited to room temperature measurements of the mid to far infrared. Other developments include ballistic-electron-emission microscopy, a next-generation spacecraft on-board computer using the Direct Memory Access Co-Processor, a 1-sq cm custom chip with 40,000 transistors, new neural network chips, the third-generation hypercube, and a new Hyperswitch Adaptive Message routing VLSI chip.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Aerospace America (ISSN 0740-722X); 28; 20-23
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  • 15
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    Quasilinear saturation of forced current sheet tearing modes (1990)
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    Publication Date: 2011-08-19
    Description: Numerical studies of tearing modes in a nearly singular forced current sheet equilibrium (Liewer and Payne, 1990) show that the modes saturate quasilinearly when the width of the magnetic island formed by the reconnection is on the order of several times the linear mode width which scales as approximately (kS) exp -2/5, where S is the Lundquist number and k is the wavenumber. The modes saturate quasilinearly by flattening the current profile, converting magnetic energy into plasma energy. The longer wavelength modes, which saturate at higher levels, release the most energy. These modes may, nonlinearly, play a role in coronal heating when sharp current sheets form as a result of global magnetic stresses.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2047-205
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  • 16
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    Heliospheric shocks and catastrophe theory (1990)
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    Publication Date: 2011-08-19
    Description: Various configurations of forward and reverse shocks that occur in the outer heliosphere can be classified using catastrophe theory. The existence of a forward shock is associated with a local maximum of a polynomial, and the existence of a reverse shock is associated with a local minimum of a polynomial. A configuration with N forward shocks and N reverse shocks corresponds to a polynomial with N maxima and N minima. The formation of forward and reverse shocks corresponds to the creation of maxima and minima of a polynomial, which is described by the separatrices of the catastrophes. The coalescence of two forward (reverse) shocks corresponds to the situation when two maxima (minima) of a polynomial have equal values, and the interaction of a forward shock with a reverse shock corresponds to a polynomial with a local maximum equal to a local minimum; these situations are described by the Maxwell sets of the appropriate catastrophes.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 1633-163
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  • 17
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    Space-based measurements of elemental abundances and their relation to solar abundances (1990)
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    Publication Date: 2011-08-19
    Description: The Ion Composition Instrument (ICI) aboard the ISEE-3/ICE spacecraft was in the solar wind continuously from August 1978 to December 1982. The results made it possible to establish long-term average solar wind abundance values for helium, oxygen, neon, silicon, and iron. The Charge-Energy-Mass instrument aboard the CCE spacecraft of the AMPTE mission has measured the abundance of these elements in the magnetosheath and has also added carbon, nitrogen, magnesium, and sulfur to the list. There is strong evidence that these magnetosheath abundances are representative of the solar wind. Other sources of solar wind abundances are Solar Energetic Particle experiments and Apollo lunar foils. When comparing the abundances from all of these sources with photospheric abundances, it is clear that helium is depleted in the solar wind while silicon and iron are enhanced. Solar wind abundances for carbon, nitrogen, oxygen, and neon correlate well with the photospheric values. The incorporation of minor ions into the solar wind appears to depend upon both the ionization times for the elements and the Coulomb drag exerted by the outflowing proton flux.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 128; 195-201
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  • 18
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    Periodicities in the occurrence rate of solar proton events (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Power spectral analyses of the time series of solar proton events during the past three solar cycles reveal a periodicity around 154 days. This feature is prominent in all of the cycles combined, cycles 19 and 21 individually, but is only weak in cycle 20. These results are consistent with the presence of similar periodicities between 152 and 155 days in the occurrence rate of major solar flares, the sunspot blocking function (Ps), the 10.7 cm radio flux (F10.7), and the sunspot number (Rz). This suggests that the circa 154-days periodicity may be a fundamental characteristic of the sun. Periods around 50-52 days are also found in the combined data set and in the three individual cycles, in general agreement with the detection of this periodicity in major flares in cycle 19, and in Ps, F10.7, and Rz in cycle 21. The cause of the 155 day period remains unknown. The spectra contain lines (or show power at frequencies) consistent with a model in which the periodicity is caused by differential rotation of active zones and a model in which it is related to beat frequencies between solar oscillations, as proposed by Wolff (1974, 1983).
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 128; 415-422
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  • 19
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    Stochastic Fermi acceleration in solar flares (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Proton spectra, valid from non- to ultra-relativistic energies, resulting from stochastic Fermi acceleration in solar flares are calculated. These spectra were obtained by numerically solving the Fokker-Planck equation, in which the escape of the particles from the acceleration region is characterized by an energy-independent escape time. In addition to equilibrium spectra, time-dependent energy spectra showing the approach to equilibrium are also presented. These numerical equilibrium spectra are compared with previous results which were obtained either by Monte Carlo simulations or approximate analytical treatments. There are no analytic solutions valid in the transrelativistic regime, which is very important for the production of pions and neutrons in solar flares. The acceleration efficiency is related to physical parameters, in particular the energy density in either magnetosonic or Alfven waves, and a lower limit is placed on either of these energy densities from acceleration times implied by gamma-ray observations. Also discussed is the physical interpretation of the escape time.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 701-708
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  • 20
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    On-board switching and processing (1990)
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    Publication Date: 2011-08-19
    Description: Findings from NASA's space electronics division's (SED's) advanced systems studies related to future communications satellite services that will require onboard switching and processing technology are reviewed. SED's digital signal switching and processing technology program is reviewed. This program responds to specific systems technology development needs for enabling commercial development of future satellite services. The technologies include: modulators, demodulators, and forward error-correction hardware for space- and ground-based applications; onboard information switching and processing, onboard network control, and health monitoring; and cost-efficient ground terminals. The in-house systems integration, test, and evaluation (SITE) project, which includes a laboratory testbed for evaluating technology in a simulated systems environment, is reviewed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE, Proceedings (ISSN 0018-9219); 78; 1206-121
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  • 21
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    Measurement and analysis of a microwave oscillator stabilized by a sapphire dielectric ring resonator for ultra-low noise (1990)
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    Publication Date: 2011-08-19
    Description: Phase-noise measurements are presented for a microwave oscillator whose frequency is stabilized by a whispering-gallery sapphire ring resonator with Q of 200,000. This mode involves little metallic conduction and allows nearly full use of the very low dielectric loss in sapphire. Several mode families have been identified, in good agreement with frequency calculations. For a 5-cm wheel resonator in a 7.6-cm container, Q values above 100,000 were found at room temperature for all of the modes in this sequence. Coupling Q-values for these same modes ranged from 10,000 (n = 5) to 100,000 (n = 10) for a WR112 waveguide port at the center of the cylinder wall of the containing can. Phase noise measurements for a transistor oscillator locked to the n = 10 (7.84-GHz) mode showed a 1/f cubed dependence for low offset frequencies, and a value of L(f) = -55 dB/Hz at an offset of 10 Hz from the carrier.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (ISSN 0885-3010); 37; 339-346
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  • 22
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    Dynamical evolution of twisted magnetic flux tubes. I - Equilibrium and linear stability (1990)
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    Publication Date: 2011-08-19
    Description: The three-dimensional dynamical evolution of twisted magnetic flux tubes is studied using a time-dependent magnetohydrodynamic (MHD) model. The flux tubes are intended to model solar coronal loops, and include the stabilizing effect of photospheric line tying. The model permits the complete evolution of flux tubes to be followed self-consistently, including the formation, equilibrium, linear instability, and nonlinear behavior. Starting from an initial uniform background magnetic field, a twisted flux tube is created by the application of slow, localized photospheric vortex flows. The flux tube evolves quasi-statically through sequences of equilibria with increasing twist, until it becomes linearly unstable to an ideal MHD kink mode. In this paper, the equilibrium properties and the linear stability behavior are discussed. The application of the method to the uniform-twist, Gold-Hoyle field confirms the previous stability threshold for kink instability and provides estimates of the resulting growth rate.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 690-700
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  • 23
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    Basic formulas find oscillator power gain (1990)
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    Publication Date: 2011-08-19
    Description: Traditional circuit analysis defines the power gain of an oscillator to be finite, since there is an output without an input. By defining power gain as the ratio of output power to input power, however, finite power gain can be characterized. Several simple circuit equations which can be used to find power gain in an oscillator circuit are presented and discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Microwaves & RF (ISSN 0745-2993); 29; 127-129
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  • 24
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    Magnetic field structure of interplanetary magnetic clouds at 1 AU (1990)
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    Publication Date: 2011-08-19
    Description: Interplanetary magnetic clouds emerge as a feature of the solar wind at 1 AU, exhibiting enhanced field strength and lower plasma temperature and density than the surrounding plasma. A least-squares program has been developed which fits magnetic field data within a cloud, while estimating such cloud properties as its size, maximum field strength, and axis inclination. The results obtained from a study of 12 clouds observed at 1 AU point to a probable cloud axis direction within 15 deg of the ecliptic plane and about 100 deg from the sun's direction, when projected into the ecliptic plane. A wide variety of orientations is observed; some extend to 80 deg from the ecliptic.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 11957-11
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  • 25
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    Gated photomultiplier response characterization for DIAL measurements (1990)
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    Publication Date: 2011-08-19
    Description: The characteristics of various detector responses are studied to understand the cause of various systematic biases and to minimize these undesirable effects in measurements of transient signals with large dynamic range. Signal-induced bias, gain variation, and the linearity of commonly used gated photomultipliers in the current integrating mode are quantitatively evaluated. Analysis of the results indicates that impurity ions inside the photomultiplier tubes (PMT) are the source of the signal induced bias and gain variation. Two different PMTs used in this study show significant differences in the magnitude and decay behavior of signal-induced bias. It was found that it can be minimized by using an external amplifier to reduce PMT gain, and by applying a low potential between the cathode and first dynode. The linearity of a PMT is also studied over a large dynamic range of input intensities employing a new technique which does not require an absolute calibration. The result of this study shows that the photomultiplier response is linear only for a limited input intensity range below a certain anode current.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Optics (ISSN 0003-6935); 29; 3303-331
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  • 26
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    Prominence formation in a coronal loop (1990)
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    Publication Date: 2011-08-19
    Description: A model is presented which depends on the preferential deposition of heating in the legs of a coronal loop and which produces a stable prominence-scale condensation at the loop top. Dynamic stability is attained by the subsequent adjustment of local parallel gravity by a magnetic inversion at the loop (or arcade) apex. A nonlinear numerical simulation of this process, which includes a deep chromosphere, a heating rate with a fixed dissipation length, and full solar gravity is described.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 359; 228-231
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  • 27
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    Programmable synaptic devices for electronic neural nets (1990)
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    Publication Date: 2011-08-19
    Description: The architecture, design, and operational characteristics of custom VLSI and thin film synaptic devices are described. The devices include CMOS-based synaptic chips containing 1024 reprogrammable synapses with a 6-bit dynamic range, and nonvolatile, write-once, binary synaptic arrays based on memory switching in hydrogenated amorphous silicon films. Their suitability for embodiment of fully parallel and analog neural hardware is discussed. Specifically, a neural network solution to an assignment problem of combinatorial global optimization, implemented in fully parallel hardware using the synaptic chips, is described. The network's ability to provide optimal and near optimal solutions over a time scale of few neuron time constants has been demonstrated and suggests a speedup improvement of several orders of magnitude over conventional search methods.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Control and Computers (ISSN 0315-8934); 18; 2, 19; 37-41
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  • 28
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    Complex permittivity of lanthanum aluminate in the 20 to 300 K temperature range from 26.5 to 40.0 GHz (1990)
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    Publication Date: 2011-08-19
    Description: Dielectric constants of microwave substrates are required in the design of superconducting microwave circuits at various temperatures. In this paper, the results are reported of a study of the complex permittivity of the newly developed lanthanum aluminate (LaAlO3) substrate, in the 20 to 300 K temperature range at frequencies from 26.5 to 40.0 GHz. The value of the complex permittivity was obtained by measuring the sample scattering parameters using a microwave waveguide technique. It is observed that, while the dielectric constant did not change appreciably with frequency, its value decreased by approximately 14 percent from room temperature to 20 K.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Microwave and Optical Technology Letters (ISSN 0895-2477); 3; 11-13
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    Magnetohydrodynamic modeling of the solar corona (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The ideal and resistive magnetohydrodynamic (MHD) model is used to examine the dynamics and structure of the solar corona. When the coronal magnetic field is deformed by photospheric flow it can evolve to states that become unstable to ideal MHD modes. The nonlinear evolution of these instabilities can lead to the generation of current sheets, field line reconnection, and energy release. The disruption of an arcade field and the kinking of coronal loops is described. The braiding of the large-scale coronal field by convective photospheric motions develops fine-scale structure in the magnetic field and leads to the development of intense current filaments. The resistive dissipation of these currents can provide an efficient coronal heating mechanism.
    Keywords: SOLAR PHYSICS
    Type: Physics of Fluids B (ISSN 0899-8221); 2; 6, pt; 1450-145
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    High-performance fault-tolerant VLSI systems using micro rollback (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A technique called micro rollback, which allows most of the performance penalty for concurrent error detection to be eliminated, is presented. Detection is performed in parallel with the transmission of information between modules, thus removing the delay for detection from the critical path. Erroneous information may thus reach its destination module several clock cycles before an error indication. Operations performed on this erroneous information are undone using a hardware mechanism for fast rollback of a few cycles. The implementation of a VLSI processor capable of micro rollback is discussed, as well as several critical issues related to its use in a complete system.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Computers (ISSN 0018-9340); 39; 548-554
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    Limits to derived flare properties using estimates for the background fluxes - Examples from GOES (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method has been presented for restricting the random derived flare temperatures and emission measures. The method is based on three tests and is applicable not only to disk-integrated observations, but also for any high-resolution observations that cannot distinguish the emissions from flaring and nonflaring plasma. The first two tests are based on the assumption that both the temperature and the emission measure should increase as the flare flux rises. The third assumes that the preflare temperature of the plasma that flares should exceed the temperature averaged over all other emitting sources. These tests were applied to two solar flares to illustrate the improvements in the derived flare properties. It is shown that flare properties do not always lie between those derived by the use or subtraction of the total preflare flux. The flare properties can, however, be bounded by subtracting and using the long- and short-wavelength preflare fluxes, respectively.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 733-742
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    Solar wind and coronal structure near sunspot minimum - Pioneer and SMM observations from 1985-1987 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Changes in solar wind speed and magnetic polarity observed at the Pioneer spacecraft are discussed here in terms of the changing magnetic geometry implied by SMM coronagraph observations over the period 1985-1987. The pattern of recurrent solar wind streams, the long-term average speed, and the sector polarity of the interplanetary magnetic field all changed in a manner suggesting both a temporal variation, and a changing dependence on heliographic latitude. Coronal observations during this epoch show a systematic variation in coronal structure and the magnetic structure imposed on the expanding solar wind. These observations suggest interpretation of the solar wind speed variations in terms of the familiar model where the speed increases with distance from a nearly flat interplanetary current sheet, and where this current sheet becomes aligned with the solar equatorial plane as sunspot minimum approaches, but deviates rapidly from that orientation after minimum.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 8231-824
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  • 33
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    Comparison between analytical models and finite-difference simulations in transmission-line tap resistors and L-type cross-Kelvin resistors (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Approximate analytical models of the transmission-line tap resistor and the cross-Kelvin resistor are compared with computer-simulated pseudo-three-dimensional resistor network models. The analytical formulas are in good agreement with the simulations over a useful range of parameters and are readily applied to the extraction of the contact resistivity and the sheet resistances of the semiconducting layer under and outside the contacts. The extraction procedure, which is easily implemented on a personal computer, is carried out for the case of alloyed AuGeNi/GaAs contacts, illustrating the importance of (1) distinguishing between layer sheet resistance under and outside the contacts and (2) considering two-dimensional current flow in the semiconducting layer.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Electron Devices (ISSN 0018-9383); 37; 1099-110
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    A bit-serial VLSI array processing chip for image processing (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An array processing chip integrating 128 bit-serial processing elements (PEs) on a single die is discussed. Each PE has a 16-function logic unit, a single-bit adder, a 32-b variable-length shift register, and 1 kb of local RAM. Logic in each PE provides the capability to mask PEs individually. A modified grid interconnection scheme allows each PE to communicate with each of its eight nearest neighbors. A 32-b bus is used to transfer data to and from the array in a single cycle. Instruction execution is pipelined, enabling all instructions to be executed in a single cycle. The 1-micron CMOS design contains over 1.1 x 10 to the 6th transistors on an 11.0 x 11.7-mm die.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Journal of Solid-State Circuits (ISSN 0018-9200); 25; 364-368
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  • 35
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    Evidence for halo-like radio sources from kilometric type III burst observations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The radio azimuths for many kilometric type III bursts that originate near or behind the limb of the sun are observed to drift far to the east or far to the west of the spacecraft-sun line. It is shown that the behavior of the observed burst parameters for these events corresponds to the response of a spinning dipole antenna to halolike sources of radiation around the sun. These results provide evidence for a previous suggestion that behind-the-limb type III events should appear as halolike sources of radiation to an observer on the opposite side of the sun, due to scattering of the radiation from the primary source back around the sun.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 125; 371-388
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    Transformation of vector magnetograms and the problems associated with the effects of perspective and the azimuthal ambiguity (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Off-center vector magnetograms which use all three components of the measured field provide the maximum information content from the photospheric field and can provide the most consistent potential field independent of the viewing angle by defining the normal component of the field. The required transformations of the magnetic field vector and the geometric mapping of the observed field in the image plane into the heliographic plane have been described. Here we discuss the total transformation of specific vector magnetograms to detail the problems and procedures that one should be aware of in analyzing observational magnetograms. The effect of the 180-deg ambiguity of the observed transverse field is considered as well as the effect of curvature of the photosphere. Specific results for active regions AR 2684 (September 23, 1980) and AR 4474 (April 26, 1984) from the Marshall Space Flight Center Vector magnetograph are described which point to the need for the heliographic projection in determining the field structure of an active region.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 126; 21-36
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    A solar cycle timing predictor - The latitude of active regions (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A 'Spoerer butterfly' method is used to examine solar cycle 22. It is shown from the latitude of active regions that the cycle can now be expected to peak near November 1989 + or - 8 months, basically near the latter half of 1989.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 125; 185-189
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  • 38
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    Solar constant secular changes (1990)
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    Publication Date: 2011-08-19
    Description: A recent model for solar constant secular changes is used to calculate a 'proxy' solar constant for: (1) the past four centuries, based upon the sunspot record, (2) the past nine centuries, based upon C-14 observations and their relation to solar activity, and (3) the next decade, based upon a dynamo theory model for the solar cycle. The proxy solar constant data is tabulated as it may be useful for climate modelers studying global climate changes.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 125; 179-184
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  • 39
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    On the level of skill in predicting maximum sunspot number - A comparative study of single variate and bivariate precursor techniques (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The level of skill in predicting the size of the sunspot cycle is investigated for the two types of precursor techniques, single variate and bivariate fits, both applied to cycle 22. The present level of growth in solar activity is compared to the mean level of growth (cycles 10-21) and to the predictions based on the precursor techniques. It is shown that, for cycle 22, both single variate methods (based on geomagnetic data) and bivariate methods suggest a maximum amplitude smaller than that observed for cycle 19, and possibly for cycle 21. Compared to the mean cycle, cycle 22 is presently behaving as if it were a +2.6 sigma cycle (maximum amplitude of about 225), which means that either it will be the first cycle not to be reliably predicted by the combined precursor techniques or its deviation relative to the mean cycle will substantially decrease over the next 18 months.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 125; 143-155
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  • 40
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    On the average rate of growth in sunspot number and the size of the sunspot cycle (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The average rate of growth in sunspot number over selected time intervals and the maximum average value as they both relate to the size of the cycle are examined, in order to predict the size of cycle 22. The predictions are compared with those of Wilson (1990) to determine whether a consensus is apparent. The average rate of growth during the ascending portion of the sunspot cycle, defined as the difference in smoothed sunspot number values between elapsed time t and sunspot minimum divided by t, is shown to correlate with the size of the sunspot cycle, especially for t greater or equal to 18 months. The maximum value of the average rate of growth is also shown to highly correlate (r = 0.98) with the size of the cycle. Using 4.5 as the maximum value of the average rate of growth, a lower limit for R(M) is estimated. The results show that the findings are consistent with the previous single variate predictions for R(M) for cycle 22.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 125; 133-141
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  • 41
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    Solid-state reprogrammable analog resistive devices for electronic neural networks (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The fabrication and performance of WO3-based, solid-state, three-terminal device configurations as programmable analog memory elements are reported. These transistorlike device structures exhibit good resistance progammability with a remarkable resolution of a few percent of the resistive strength over a four orders of magnitude dynamic range. The most critical component of these devices is an insulating layer between the active WO3 and the cation donor layer. The progamming characteristics and operation mechanisms of the device are described, and probable reaction mechanisms critical to the device stability are discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 137; 1935-193
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    The heliopause (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A Pioneer or Voyager spacecraft will soon pass through one of the last major frontiers in the solar system - the heliospheric terminal shock. Some unknown, but perhaps small, distance beyond the terminal shock is the heliopause, marking the final boundary between solar-wind and Galactic plasmas and the final goal of these spacecraft. This occasion offers an opportunity to obtain a wealth of information on the properties of the Galaxy, the interstellar medium, and the large-scale interactions of that medium with stellar winds. Several tentative remote detections of the shock place it just beyond the present spacecraft locations. However, uncertainties in the physical processes and parameters that determine the location of the boundary lead to equal uncertainties in predicting which of the spacecraft will reach it first.
    Keywords: SOLAR PHYSICS
    Type: Reviews of Geophysics (ISSN 8755-1209); 28; 97-115
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    Sub-arcsecond observations of the solar X-ray corona (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results from a high-resolution multi-layer-coated X-ray imaging telescope, part of the Normal Incidence X-ray Telescope sounding rocket payload are presented. Images of the peak of a two-ribbon flare showed detailed structure within each ribbon, as well as the expected bright arches of emission connecting the ribbons. The number of X-ray bright points is small, consistent with predictions based on the previous solar cycle. Topology of the magnetic structure is complex and highly tangled, implying that the magnetic complexity of the photosphere is paralleled in the corona.
    Keywords: SOLAR PHYSICS
    Type: Nature (ISSN 0028-0836); 344; 842-844
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    Linear tearing modes of a forced current-sheet equilibrium (1990)
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    Publication Date: 2011-08-19
    Description: Linear tearing modes are studied in a nearly singular forced current-sheet equilibrium, such as could result from global magnetic forces in the solar corona. Growth rates for the tearing modes, determined by solving the linearized reduced MHD (Strauss) equations numerically, were found to scale as (gamma)tau(d) = about S exp 4/5 k(y) exp 4/5, where S is the Lundquist number, k(y) is the wavenumber, and tau(d) is the classical resistive diffusion time. This scaling is in agreement with predictions from analytical theory. Because of the faster S scaling of these modes compared to the tearing modes of a diffuse current-sheet equilibrium, the modes have much higher growth rates (by a factor of about 10,000) for coronal values of S (about 10 to the 12th). For coronal parameters, the growth times of these new modes are estimated to be on the order of several hours to days, as compared to growth times of months to years for the tearing modes in a diffuse current-shear equilibrium. The growth times are comparable to reconnection times scales required in models of coronal heating by magnetic field dissipation.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 353; 658-665
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    Turbulent polar heliospheric fields (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent observational studies of interplanetary field fluctuations and MHD simulation results are used to suggest that the turbulent evolution of the fields over the solar poles leads to a state intermediate between the large fields of the static limit and the small fields given by 'saturation' (deltaB/B = about 1). In particular, assuming the strength of the coronal hole sources of fluctuations are similar in all solar regions, the polar fluctuations in the outer heliosphere are likely to be nearly isotropic, with amplitudes somewhat smaller than those predicted by the WKB extrapolation from 1 AU in the ecliptic plane.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 567-570
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    The nonlinear evolution of magnetized solar filaments (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Thermal instability driven by optically thin radiation is believed to initiate the formation of plasma filaments in the solar corona. The fact that filaments are observed generally to separate regions of opposite, line-of-sight, magnetic polarity in the underlying photosphere suggests that filament formation requires the presence of a highly sheared, local magnetic field. Two-dimensional, nonlinear, magnetohydrodynamic simulations of the local genesis and growth of solar filaments in a force-free, sheared, magnetic field were performed, and the evolution of generic perturbations possessing broad spatial profiles was traced. It was found that simulations of the evolution of initial random-noise perturbations produce filamentary plasma structures that exhibit densities and temperatures characteristic of observed solar filaments. Furthermore, in each of these simulations, the filament axis lies at a finite angle with respect to the local magnetic field, consistent with solar observations.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 353; 297-312
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    A heliospheric vortex street? (1990)
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    Publication Date: 2011-08-19
    Description: This paper presents the hypothesis that the periodic meridional (north-south) flow observed by Voyager 2 in the neighborhood of 20-25 AU were produced by a heliospheric vortex street. The separation of the vortices was approximately 6 AU in the radial direction, and the vortices were carried away from the sun at a speed of approximately 425 km/s. This hypothesis can account for the observed + or - 5 degree deflections in the flow with a period of 25.5 days, and it predicts small amplitude fluctuations in the bulk speed with two maxima per solar rotation, which is consistent with observations in 1986.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 4333-433
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    Coalescence of recurrent streams of different sizes and amplitudes (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Two corotating streams per solar rotation, separated by the heliospheric plasma sheet, were observed at 1 AU during 1974, and the streams recurred four times during the interval from day 145 to day 255. A single compound stream per solar rotation was observed at 5.5 - 6.0 AU during the corresponding interval from day 165 to day 275, indicating that the two recurrent streams observed at 1 AU coalesced between 1 AU and 6 AU. The average maximum speed of one of the recurrent streams was 805 km/s while that of the other recurrent stream was 705 km/s. The compound stream was not formed by the overtaking of the slow stream by the fast stream. Rather, it was probably formed by a process involving both filtering (due to the fact that the slow stream was 50 percent wider than the fast stream) and a geometrical effect.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 4247-425
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    MHD simulations of coronal mass ejections - Importance of the driving mechanism (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The importance of the form of the driving mechanism in MHD simulations of coronal mass ejections is investigated. A model simulation problem is devised, and it is found that the use of a simple form for the initial corona, with an upward moving parcel of cold, dense plasma as the driving mechanism, can produce results that are consistent with many of the features observed by coronagraphs. The results imply that the nature of the driving mechanism may play an important role in determining the dynamical evolution of mass ejections.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 4229-423
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    The amplitudes of interplanetary fluctuations - Stream structure, heliocentric distance, and frequency dependence (1990)
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    Publication Date: 2011-08-19
    Description: A study is presented of the heliocentric distance, frequency, and stream structure dependence of the amplitudes of interplanetary fluctuations in the velocity and magnetic field from 0.3 to nearly 20 AU and for spacecraft-frame periods of 10 days to a few hours. Evidence is presented that, at a given heliocentric distance, the amplitude of the magnetic field fluctuations is proportional to the magnitude of the field, nearly independently of the solar wind speed. The radial evolution of magnetic fluctuations is shown to be nearly consistent with WKB expectations except at smaller scales in the inner heliosphere and at the largest scales in the outer heliosphere. While the large-scale velocity fluctuations are kinetic energy-dominated in the inner heliosphere due to the presence of streams, the magnetic fluctuation energy eventually comes to be slightly dominant over the kinetic energy at all scales. The theoretical implications of the results are considered.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 4203-421
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    An electronically tuned, stable 8415 MHz dielectric resonator FET oscillator for space applications (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A voltage-controlled 8415-MHz FET oscillator stabilized by a dielectric resonator is described. The oscillator provides over 3.2-MHz linear electronic tuning range with a flat power output equal to +1.8 dBm (27 C, nominal), a single-sideband noise-to-carrier ratio of -68 dBc/Hz at 1 kHz off carrier, and a frequency-temperature coefficient of 0.54 parts per million/C over a -24 C to 75 C range. The oscillator withstood 150 Krads (Si) of gamma radiation with no significant performance degradation. The overall performance of the FET oscillator is far superior in many ways to that of an equivalent bipolar oscillator for space applications. For space applications, the FET dielectric resonator oscillator (DRO) is preferred over bipolar DRO because of its lower DC power consumption, better thermal frequency stability, linear electronic tunability, and higher RF output power capability.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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    High Tc superconducting IR detectors from Y-Ba-Cu-O thin films (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A thin-film high-Tc superconducting multielement optical detector made of Y-Ba-Cu-O has been designed and evaluated using optical pulses from a diode laser (830 nm) and a Q-switched CO2-laser (10.6 microns). Different thin films have been tested. A laser deposited film showed the strongest response amplitude for short pulses and responded to an ultrafast, 50 ps wide pulse. Comparisons between dR/dT and response as a function of temperature indicated, however, a bolometric response.
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    Microwave applications and characterization of the microwave properties of high temperature superconducting films (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The development by NASA JPL of high-temperature superconductors (HTSs) for use in microwave circuit elements is discussed. The synthesis of HTS films and characterization of their microwave absorption are reviewed. Applications to cryogenic low-noise receivers, spacecraft microwave systems, and low-noise oscillators are considered.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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    High temperature superconducting thin film microwave circuits - Fabrication, characterization, and applications (1990)
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    Publication Date: 2011-08-19
    Description: Epitaxial YBa2Cu3O7 films were grown on several microwave substrates. Surface resistance and penetration depth measurements were performed to determine the quality of these films. Here, the properties of these films on key microwave substrates are described. The fabrication and characterization of a microwave ring resonator circuit to determine transmission line losses are presented. Lower losses than those observed in gold resonator circuits were observed at temperatures lower than critical transition temperature. Based on these results, potential applications of microwave superconducting circuits such as filters, resonators, oscillators, phase shifters, and antenna elements in space communication systems are identified.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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    A three-dimensional simulation of a coronal streamer (1990)
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    Publication Date: 2011-08-19
    Description: A time-dependent MHD simulation was used to investigate the magnetic topology of an idealized streamerlike configuration in three dimensions. Starting from an initially current-free multipole field and a transonic flow, a quasi-steady, streamerlike configuration forms. The simulated streamer exhibits a closed magnetic field region bounded by a current layer and surrounded by open fields. This helmet region is surmounted by a current layer, with an enhanced density in the closed field and current sheet regions. The simulated streamer has a finite longitudinal extent, with the closed field region primarily confined to the center of the structure.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2281-228
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    Concerning the extrapolation of solar nonlinear force-free magnetic fields (1990)
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    Publication Date: 2011-08-19
    Description: This paper contains a review and discussion of the mathematical basis of the extrapolation techniques involved in using photospheric vector magnetograms to obtain the coronal field above the surface. The two basic techniques employing the Cauchy initial value problem and the variational techniques are reviewed in terms of the mathematical and practical applications. A short review is presented of the current research on numerical modeling techniques in the area of extrapolating vector magnetograms; specifically, algorithms to extrapolate nonlinear force-free magnetic fields from the photosphere are considered.
    Keywords: SOLAR PHYSICS
    Type: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 61; 2, 19
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    Heating of the corona by magnetic singularities (1990)
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    Publication Date: 2011-08-19
    Description: Theoretical models of current-sheet formation and magnetic heating in the solar corona are examined analytically. The role of photospheric connectivity in determining the topology of the coronal magnetic field and its equilibrium properties is explored; nonequilibrium models of current-sheet formation (assuming an initially well connected field) are described; and particular attention is given to models with discontinuous connectivity, where magnetic singularities arise from smooth footpoint motions. It is shown that current sheets arise from connectivities in which the photospheric flux structure is complex, with three or more polarity regions and a magnetic null point within the corona.
    Keywords: SOLAR PHYSICS
    Type: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 61; 2, 19; 369-382
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    The significance of vector magnetic field measurements (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of four flaring solar active regions, obtained during 1980-1986 with the NASA Marshall vector magnetograph (Hagyard et al., 1982 and 1985), are presented graphically and characterized in detail, with reference to nearly simultaneous Big Bear Solar Observatory and USAF ASW H-alpha images. It is shown that the flares occurred where local photospheric magnetic fields differed most from the potential field, with initial brightening on either side of a magnetic-neutral line near the point of maximum angular shear (rather than that of maximum magnetic-field strength, typically 1 kG or greater). Particular emphasis is placed on the fact that these significant nonpotential features were detected only by measuring all three components of the vector magnetic field.
    Keywords: SOLAR PHYSICS
    Type: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 61; 2, 19
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    Hallmarks of the magnetic field in the solar atmosphere - Structure, evolution, heating, and flaring (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent observations of the solar magnetic field and its effects on the solar atmosphere are discussed, with an emphasis on large-scale active regions and their implications for the fine-scale magnetic structure and for activity in the so-called quiet regions. Sample magnetograms, sunlight images, H-alpha images, X-ray images, and spectroheliograms are presented and characterized in detail, and the form and action of the magnetic field in flares are considered. It is pointed out that simultaneous observations of all levels (from the photosphere to the corona) at 100-km (about 100-marcsec) resolution are needed to see the extent of fields looping into the corona and understand their structure and activity; large space-based observatories would be required.
    Keywords: SOLAR PHYSICS
    Type: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 61; 2, 19
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  • 60
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    An estimator-predictor approach to PLL loop filter design (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The design of digital phase locked loops (DPLL) using estimation theory concepts in the selection of a loop filter is presented. The key concept, that the DPLL closed-loop transfer function is decomposed into an estimator and a predictor, is discussed. The estimator provides recursive estimates of phase, frequency, and higher-order derivatives, and the predictor compensates for the transport lag inherent in the loop.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Communications (ISSN 0090-6778); 38; 1667-166
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  • 61
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    Performance of all-NbN superconductive tunnel junctions as mixers at 205 GHz (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Small-area (1x1 sq micron) high-current-density NbN-MgO-NbN tunnel junctions with I-V characteristics suitable for high frequency mixers were fabricated. These junctions are integrated with superconducting microstrip lines designed to resonate out the large junction capacitance. The mixer gain and noise performance were studied near 205 GHz as a function of the inductance provided by the microstrip. This has yielded values of junction capacitance of 85 fF/sq microns and magnetic penetration depth of 3800 angstroms. Mixer noise as low as 133 K has been obtained for properly tuned junctions. This is the best noise performance ever reported for an NbN SIS mixer.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Physica B (ISSN 0921-4526); 165-166; 75
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  • 62
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    Cable delay compensator for microwave signal distribution over optical fibers (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The basic principles of microwave fiber-optic systems are outlined with emphasis on fiber-optic cable delay compensators (CDC). Degradation of frequency and phase stability is considered, and it is pointed out that the long-term stability of a fiber-optic link is degraded by group delay variations due to temperature fluctuations in the optical fiber and low-frequency noise characteristics of the laser. A CDC employing a voltage-controlled oscillator to correct for phase variations in the optical fiber is presented, and the static as well as dynamic closed-loop analyses of the fiber-optic CDC are discussed. A constructed narrow-band fiber-optic CDC is shown to reduce phase variations caused by temperature fluctuations by a factor of 400. A wide-band CDC utilizing a temperature-controlled coil of fiber to compensate for phase delay is also proposed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Microwave Journal (ISSN 0192-6225); 33; 81-83
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  • 63
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    p-mode absorption in the giant active region of 10 March, 1989 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The interaction of solar p-mode oscillations with solar active regions has been studied in the case of the velocity oscillations observed in the vicinity of NOAA region 5359 on March 10, 1989. A maximum of nearly 70 percent of the power of incident high-degree modes is noted to be absorbed by this exceptionally large sunspot group. The occurrence of a major flare within this region during the observing sequence furnished a unique opportunity for testing the hypothesis that flares can excite photospheric acoustic waves. A search for acoustic 'pulses' emanating from the flare leads no detection of pulses, to a level of about 20 percent of the background power.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 129; 83-94
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  • 64
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    Relaxation of the loss-cone by quasi-linear diffusion of the electron-cyclotron maser instability in the solar corona (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A self-consistent numeric two-dimensional code using kinetic-wave particle equations has been developed and applied to the maser dynamics of the solar corona. Time histories generated by the code reveal details of the evolution of the linear phase, the saturation and subsequent relaxation of the loss cone. Quantitative values are obtained for the saturation time, the amount of the converted free energy, the critical wave energy level for onset of maser diffusion, the velocity and pitch angle range of the resonant particles, and the relative importance of the different magnetoionic modes and harmonics. A wide range of initial conditions is covered by varying the loss-cone distribution and the ambient cold plasma parameters.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 85; 3, No
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  • 65
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    Numerical simulation of solar wind density fluctuations and their effects on VLF radio interferometry (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A mission consisting of an array of small satellites has been proposed to investigate radio sources at frequencies from approximately 2 to 20 MHz, a range unobservable from the ground because of ionospheric absorption and aberrations. Such a mission seems feasible and relatively inexpensive, but further investigation is still necessary. The solar wind is a major concern because it contains turbulence-induced random density variations that cause a fluctuating phase shift in any electromagnetic signal passing through, sometimes making radio source imaging by interferometry impossible. A numerical simulation has been developed which attempts to accurately characterize solar wind density fluctuations. Results have allowed more concrete conclusions to be drawn about observing constraints and have shown that interferometric imaging at radio frequencies below 10 MHz with baselines up to 100 km is possible at solar elongation angles of about 90 deg or more.
    Keywords: SOLAR PHYSICS
    Type: Radio Science (ISSN 0048-6604); 25; 743-755
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  • 66
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    Solar minimum Lyman alpha sky background observations from Pioneer Venus orbiter ultraviolet spectrometer - Solar wind latitude variation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of interplanetary H I Lyman alpha over a large portion of the celestial sphere were made at the recent solar minimum by the Pioneer Venus orbiter ultraviolet spectrometer. These measurements were performed during a series of spacecraft maneuvers conducted to observe Halley's comet in early 1986. Analysis of these data using a model of the passage of interstellar wind hydrogen through the solar system shows that the rate of charge exchange with solar wind protons is 30 percent less over the solar poles than in the ecliptic. This result is in agreement with a similar experiment performed with Mariner 10 at the previous solar minimum.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 14855-14
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  • 67
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    Sun's inertial motion and luminosity (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Fast Fourier analysis of the detrended record of solar irradiance obtained by the Nimbus-7 cavity pyrheliometer shows a rich spectrum of significant frequencies between about 30 and 850 nHz (periods between 13 and 400 days). Wolff and Hickey (1987), elaborating on a model developed by Wolff (1974, 1976, 1983, and 1984), suggest that many of these peaks arise due to interference of rigidly rotating global solar oscillations (r- and g-modes). Their model fit is quite good in the region above about 135 nHz, but less satisfactory below this threshold. It is noted that the FFT spectrum of d-sq L/d-sq t, the second derivative of angular momentum of the solar inertial motion, contains peaks matching the large peaks in the irradiance spectrum below 400 nHz with periods near 0.08, 0.24, 0.65, and about 1 yr. The origins of the peaks in the d-sq L/d-sq t spectra are discussed, and some previous studies are reviewed bearing on the question of a possible relationship of solar motion and solar activity.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 127; 379-392
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  • 68
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    Dielectric properties measurement of substrate and support materials (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In this paper a fast and straightforward waveguide measurement technique is described for the determination of the dielectric constant and loss tangent of many commercially available materials. These dielectric materials include Cuflon, Teflon, Arlon's polyimides, Lockheed's ceramic foams, and Rogers Duroid materials. The effective dielectric constant and loss tangent of Hexsel's honeycomb material is also measured by this method and is compared to the predicted data obtained using the volume averaging theory. The accuracy and other features of this measurement technique are also discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Microwave and Optical Technology Letters (ISSN 0895-2477); 3; 283-286
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  • 69
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    An interplanetary planar magnetic structure oriented at a large (about 80 deg) angle to the Parker spiral (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Magnetic field structures in the solar wind, characterized by a variation of the field vectors within a plane inclined to the ecliptic ('Planar Magnetic Structures', PMSs), were reported recently (Nakagawa et al., 1989). These PMSs have the property that the plane of variation of the field also contains the nominal Parker spiral direction. An observation of a PMS where the direction of the line of intersection of the plane of field variation with the ecliptic plane makes a large (about 80 deg) angle to the Parker spiral direction is presented. Furthermore, the angular variables of the field (1) vary over a restricted range, and (2) are linearly related. The latter property is related to the former. Currently proposed models for the origin of PMS, inasmuch as they require field configurations which retain strict alignment with the Parker spiral direction from formation to observation, are probably incomplete.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 1025-102
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    The relationship between energetic particles and flare properties for impulsive solar flares (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The impulsive mode of particle acceleration is studied by searching for 0.2-2 MeV electron increases associated with intense type III/V bursts. It is found that the presence of a type III/V burst in association with a relatively intense flare event indicates the acceleration and escape of greater than 100 KeV electrons. A list of type III/V electron events is compiled, showing that the majority included greater than 10 MeV proton increases, although they were not followed by a type II burst. The results suggest that there are two different modes of proton acceleration with the second mode becoming significant only for larger, gradual flares.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 73; 253-258
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    Energetic particles from impulsive solar flares (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of solar energetic particles from impulsive flares are reviewed. Consideration is given to observations of electron events, He-3 rich events, and heavy-nuclei-rich events. It is found that these observations can be unified into a description of the particles from impulsive flares. The observations are compared with observations of gamma-ray line in impulsive flares and particles in flares and compared with particles in space. A model for accelerating the unique particle abundances of energetic particles is proposed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 73; 235-251
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  • 72
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    Flow downstream of the heliospheric terminal shock. I - Irrotational flow (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent reports of remote detection of the heliospheric terminal shock place it near 50 AU. These conflict with standard models which, when combined with current data on the local interstellar medium, place the shock beyod 100 AU. Resolution of this discrepancy has led to hypotheses that invoke cosmic ray pressure, momentum exchange with interstellar neutrals, and magnetic field effects between the shock and the contact discontinuity dividing the solar wind from interstellar plasma. These hypotheses depend not only on properties of the interstellar medium, but also on the downstream three-dimensional flow between the shock and the contact discontinuity, in the region called the 'heliosheath'. The downstream flow field in the absence of magnetic fields is examined here under the assumptions that the flow everywhere outside the shock can be approximated as irrotational and incompressible. It is found, in particular, that the distance between the terminal shock and the contact discontinuity is less than the heliocentric distance to the terminal shock, effectively eliminating magnetic field effects in the heliosheath as being dynamically important.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 6403-641
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  • 73
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    Chemical nature of silicon nitride-indium phosphide interface and rapid thermal annealing for InP MISFETs (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A rapid thermal annealing (RTA) process in pure N2 or pure H2 was developed for ion-implanted and encapsulated indium phosphide compound semiconductors, and the chemical nature at the silicon nitride-InP interface before and after RTA was examined using XPS. Results obtained from SIMS on the atomic concentration profiles of the implanted silicon in InP before and after RTA are presented, together with electrical characteristics of the annealed implants. Using the RTA process developed, InP metal-insulator semiconductor FETs (MISFETS) were fabricated. The MISFETS prepared had threshold voltages of +1 V, transconductance of 27 mS/mm, peak channel mobility of 1200 sq cm/V per sec, and drain current drift of only 7 percent.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 137; 1537-154
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    Ka-band propagation characteristics of microstrip lines on GaAs substrates at cryogenic temperatures (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Effective permitivity and loss characteristics of gold microstrip lines on GaAs substrates were obtained by characterizing GaAs linear resonators at cryogenic temperatures (300 to 20 K) from 30-40 GHz. A slight decrease in effective permittivity and a significant reduction in loss were observed with lower temperatures.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Microwave and Optical Technology Letters (ISSN 0895-2477); 3; 117-119
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  • 75
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    Improved high-voltage, high-frequency square-wave generator (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper describes the design and operation of a prototype high-voltage full-floating high-frequency square-wave generator which is an improved version of the generator developed by Bernius and Chutjian (1989). The present design overcomes possible momentary simultaneous ON states in the MOSFET configuration and is less susceptible to deleterious effects caused by the component aging and replacements with nonidentical parts. The circuit performs well over a wide voltage and frequency range, until a limit is imposed by the operating characteristics of the active MOSFET elements. Circuit diagrams are presented.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Review of Scientific Instruments (ISSN 0034-6748); 61; 925-927
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  • 76
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    Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Helios, IMP 8, ISEE 3, ad Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. Previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here it is shown that this evolution is not a solar cycle effect, and that the correlations become even more strongly negative at heliocentric distance larger than 9.5 AU. There is considerable variability in the distributions of the correlations at a given heliocentric distance, but this is not simply related to the solar cycle. Examination of the evolution of correlations between density and speed suggest that most of the structures responsible for evolution in the anticorrelation between n and B are not slow-mode waves, but rather pressure balance structures. The latter consist of both coherent structures such as tangential discontinuities and the more generally pervasive 'pseudosound' which may include the coherent structures as a subset.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 1087-109
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    A search for evidence of the evolution of rotational discontinuities in the solar wind from nonlinear Alfven waves (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are presented of a study designed to confirm the suspected relation between Alfven solitons (steepened Afven waves) and rotational discontinuities (RDs) in the solar wind. The ISEE 3 data were used to search for the predicted correlations between the beta value of plasma, the sense of polarization of the discontinuity, and changes of the magnetic field strength and plasma density across the discontinuity. No statistically significant evidence was found for the evolution of RDs from Alfven solitons. A possibility is suggested that the observations made could have been far from the regions in which the RDs were formed.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 13-20
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    The Ar/Ca abundance ratio in solar flares (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An Ar/Ca abundance ratio of at least 0.56 is derived using the X-ray spectra of solar flares recorded by the SOLFLEX spectrometers on the P78-1 spacecraft. The method involves determining the contribution of the Ar XVII 1s2 1S0-1s4p 1P1 line to a blended feature at 3.2005 A. This contribution is determined by considering the relationship of the other component of the blended feature, namely the Ca XVIII 1s2 2s 2S(1/2)-1s2p2s 2P(3/2) line, to the dielectronic satellite lines of Ca XVII that fall between 3.215 and 3.24 A. It is demonstrated that a broad-wavelength coverage solar X-ray spectrometer experiment is necessary for precise abundance measurements.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 348; 341-345
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  • 79
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    Spatial gradients in the heliospheric magnetic field - Pioneer 11 observations between 1 AU and 24 AU, and over solar cycle 21 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The large-scale temporal behavior and spatial gradients in the heliospheric magnetic field were investigated using magnetic field observations by Pioneer 11 and ISEE 3/ICE satellites, including observations out to a radial distance of 24 AU and over a time interval that includes the recent solar minimum. It was found that, to first order, the gradients in the magnetic field magnitude and in the azimutal component agree well with the Parker (1958) model. The analysis of the Pioneer data confirms previous reports of a magnetic field flux deficit of about 1 percent/AU, so that at 20 AU the relative deficit is of the order of 20 percent. It is argued that most of the magnetic field deficit is in the radial gradient.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 1-11
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    Numerical simulations of the rebound shock model for solar spicules (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Using time-dependent numerical simulations, the proposed rebound shock mechanism for spicules has been examined. At temperatures above a critical value, T(c), the radiation is characteristic of the conditions in the optically thin corona and near optically thin transition region. When T less than T(c), the atmosphere has a radiative cooling time, tau(rad) characteristic of chromosphere. The spicule is initiated with a quasi-impulsive force in the low chromosphere, which drives a train of upward propagating rebound shocks along the rigid magnetic flux tube. These shocks then move the transition region upward. The material below the displaced transition region has temperatures and densities similar to those of spicules when T(c) = 20,000 K or more and tau(rad) = 500 s or more, but not when T(c) = 10,000 K, and probably not when tau(rad) = 100 s. For all the cases where the cross sectional area diverges rapidly with height, the upward velocity of the transition region is less than that of spicules. Moreover, the maximum height is less than that of average spicules. Taller, higher velocity spicules result when the magnetic field cross sectional area is constant. In all cases, the rebound shock mechanism produces substantial motions and temperature and density variations in chromospheric and transition region material. It is suggested that this may be a partial explanation for the continuous dynamic state of the lower solar atmosphere.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 349; 647-655
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    Surface studies on scandate cathodes and synthesized scandates (1990)
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    Publication Date: 2011-08-19
    Description: Auger, ESCA, electron emission, evaporation, and desorption measurements were made on three different types of scandate surfaces. They are: (1) an impregnated top layer scandate cathode, (2) an unimpregnated top layer scandate cathode with a deposited barium or barium oxide adsorbate surface layer, and (3) a synthesized scandate surface, which replicates a scandate cathode surface. The purpose of these experiments was to determine the role that Sc2O3 plays in making the scandate cathode a more copious electron emitter than the conventional impregnated-type cathode. The synthesized scandate surface experiments consisted of depositing multilayer scandium on a tungsten surface, oxidizing the scandium, and then depositing either Ba or BaO on the scandium oxide surface. The results of these measurements showed that the low work function portions of the thin-film scandate cathode are where the Sc2O3 is the substrate and BaO is the adsorbate.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Electron Devices (ISSN 0018-9383); 37; 2595-260
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    Predicted extreme-ultraviolet and X-ray spectrum of a microflare-heated corona (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Sturrock et al. (1990) have proposed that a distribution of microflares produces the solar coronal and transition-region emission. This paper presents computed EUV and X-ray emission spectra from that distribution, including the effects of time-dependent ionization. The overall agreement of the predicted spectrum with observations is fairly good, although the predicted emission from the upper transition region is high by a factor of 2. Time-dependent ionization greatly enhances the He II 304-A line, improving the agreement with observation compared with ionization equilibrium models. The predicted effects on temperature-sensitive line ratios of other ions cannot yet be tested against observations due to uncertainties in instrumental calibration and atomic rates.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 365; 387-390
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    Observations of the 12.3 micron Mg I emission line during a major solar flare (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The extremely Zeeman-sensitive 12.32 micron Mg I solar emission line was observed during a 3B/X5.7 solar flare on October 24, 1989. When compared to postflare values, Mg I emission-line intensity in the penumbral flare ribbon was 20 percent greater at the peak of the flare in soft X-rays, and the 12 micron continuum intensity was 7 percent greater. The flare also excited the emission line in the umbra where it is normally absent. The umbral flare emission exhibits a Zeeman splitting 200 G less than the adjacent penumbra, suggesting that it is excited at higher altitude. The absolute penumbral magnetic field strength did not change by more than 100 G between the flare peak and postflare period. However, a change in the inclination of the field lines, probably related to the formation and development of the flare loop system, was seen.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 364; L49-L52
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    The effect of coupling line loss in microstrip to dielectric resonator coupling (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The interaction between a dielectric resonator and a microstrip transmission line is fundamentally a field phenomenon. However, the model of Figure 1b widely is used to represent the arrangement in Figure 1a, and predicts the behavior encountered in practice. The microstrip line of length l = n(lambda)/4 between the input and coupling planes and the lambda/4 open-circuit stub usually is assumed to be lossless. This paper considers the effect of coupling line loss on the unloaded-Q and coupling coefficient beta of the combination. It shows that transmission line loss can cause the decrease in unloaded-Q that has been observed to occur with tight coupling, and limits the coupling coefficient to a much lower value than would be obtained with a lossless coupling line.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Microwave Journal (ISSN 0192-6225); 33; 169
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    Infrared response from metallic particles embedded in a single-crystal Si matrix - The layered internal photoemission sensor (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Infrared radiation at wavelengths of 1-2 microns has been detected in a new device labeled the layered internal photoemission sensor. The device structure, which is grown by molecular beam epitaxy, incorporates epitaxial CoSi2 particles with dimensions of 10-50 nm. Radiation absorbed by these particles photoexcites carriers into a surrounding single-crystal silicon matrix. A peak quantum efficiency of 1.3 percent is measured, which is approximately six times higher than in planar CoSi2 Schottky diodes with 5-nm silicide thickness.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters (ISSN 0003-6951); 57; 1419-142
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  • 86
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    Novel Si(1-x)Ge(x)/Si heterojunction internal photoemission long-wavelength infrared detectors (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The feasibility of a novel p(+)-Si(1-x)Ge(x)-p-Si heterojunction internal photoemission (HIP) IR detector is demonstrated. A degenerately doped p(x)-Si(1-x)Ge(x) layer is required for strong IR absorption to generate photoexcited holes. The Si(1-x)Ge(x) layers are grown by molecular beam epitaxy, with boron concentrations up to 10 to the 20th/cu cm achieved by using an HBO2 source. Photoresponse at wavelengths ranging from 2 to 10 microns has been obtained with quantum efficiencies above 1 percent. The tailorable cutoff wavelength of the HIP detector has been demonstrated by varying the Ge composition ratio in the Si(1-x)Ge(x) layers.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters (ISSN 0003-6951); 57; 1422-142
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  • 87
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    Observational clues to the energy release process in impulsive solar bursts (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The nature of the energy release process that produces impulsive bursts of hard X-rays and microwaves during solar flares is discussed, based on new evidence obtained using the method of Crannell et al. (1978). It is shown that the hard X-ray spectral index gamma is negatively correlated with the microwave peak frequency, suggesting a common source for the microwaves and X-rays. The thermal and nonthermal models are compared. It is found that the most straightforward explanations for burst time behavior are shock-wave particle acceleration in the nonthermal model and thermal conduction fronts in the thermal model.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 73; 131-135
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  • 88
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    Solar rotation and the sunspot cycle (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Reexamination of the published sunspot rotation rates from Mount Wilson for the period from 1921 to 1982 suggests that the sun rotates more rapidly when there are fewer sunspots. This behavior is seen over the course of each cycle with the most rapid rotation usually observed at sunspot minimum. It is also seen in hemispheric differences with the southern hemisphere, having fewer spots, rotating more rapidly than the northern hemisphere. Furthermore, the rotation rate averaged over each cycle also shows that the sun rotates more rapidly during cycles with fewer sunspots and less sunspots area. This inverse correlation between sunspot area and rotation rate suggests that during the Maunder minimum the sun may have rotated slightly faster than is observed today.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 357; 271-274
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  • 89
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    Energetic particle abundances in solar electron events (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The results of a comprehensive search of the ISEE 3 energetic particle data for solar electron events with associated increases in elements with atomic number Z = 6 or greater are reported. A sample of 90 such events was obtained. The events support earlier evidence of a bimodal distribution in Fe/O or, more clearly, in Fe/C. Most of the electron events belong to the group that is Fe-rich in comparison with the coronal abundance. The Fe-rich events are frequently also He-3-rich and are associated with type III and type V radio bursts and impulsive solar flares. Fe-poor events are associated with type IV bursts and with interplanetary shocks. With some exceptions, event-to-event enhancements in the heavier elements vary smoothly with Z and with Fe/C. In fact, these variations extend across the full range of events despite inferred differences in acceleration mechanism. The origin of source material in all events appears to be coronal and not photospheric.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 357; 259-270
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  • 90
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    Nonpotential magnetic fields at sites of gamma-ray flares (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gama-ray flares is examined to determine whether there are special signatures of the stressed fields for this type of flare. Observations of the flares in the active region of April 1984 (AR 4474) are analyzed, showing that the big flare initiated at the location on the magnetic neutral line where the field deviated the most from a potential field. The nonpotential signatures of AR 4474 are compared with those of four other regions. The results suggest that gamma-ray flares are associated with strongly nonpotential fields that extend over relatively larger lengths of the magnetic neutral line that the fields associated with flares that do not produce gamma-ray events.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 73; 159-163
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  • 91
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    Workshop on Impulsive Solar Flares, 2nd, University of New Hampshire, Durham, Sept. 26-28, 1988, Proceedings (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Papers on impulsive solar flares are presented, covering topics such as the optical properties of impulsive flares, soft X-ray spectroscopy of solar flares, the energy release process in impulsive bursts, high-velocity evaporation and a high-speed shock wave during the impulsive phase of the April 24, 1984 flare, nonpotential magnetic fields at sites of gamma-ray flares, and meter-decimeter and microwave radio observations of solar flares. Other topics include rise times in solar radio bursts, removal of the gradual component in analyses of solar impulsive bursts, ion and relativistic electron transport in solar flares, neutrons and gamma-ray emission on June 3, 1982, emission characteristics of three intense solar flares in cycle 21, and solar flare gamma-ray observations with the Hinotori satellite. Additional topics include spectra of relativistic solar proton ground-level events recorded in Antarctica, a 153-d periodicity in the occurrence of solar flares producing energetic interplanetary electrons, a search for solar neutron response in neutron monitor data, neutral beams in two-ribbon flares and in the geomagnetic tail, beam heating in solar flares, and solar flare gamma-ray line shapes.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0067-0049)
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  • 92
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    Optical control of microwave devices (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Theoretical and applications aspects of optoelectronic control for microwave devices are examined in an introduction for graduate engineering students and practicing engineers. The basic features of optical MMICs are reviewed, and chapters are devoted to laser diodes, electrooptic modulators, photodetectors, microwave fiber-optic links, optoelectronic switching and gating, optoelectronic microwave signal generation, an optoelectronic switch matrix, optoelectronic switching and modulation of oscillators, and optoelectronic injection-locking and tuning of oscillators. Extensive diagrams, drawings, and graphs are provided.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 93
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    An expansion plan for the 60 Hz power distribution system at KSC: LC-39 substations load allocation plan (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The increasing load density in the LC-39 area of Kennedy Space Center (KSC) can be met by either modifying the existing substation and increasing its capacity or by planning an additional new substation. Evidence that the later approach is more economical, enhances the system reliability, and would produce more satisfactory performance indices is provided. Network theory is the basis for the optimal location determination of the proposed substation. A load reallocation plan which minimizes investment cost and power losses and meets other desirable system features is drafted. The report should be useful to the system designer and can be a useful guideline for future facility planners.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA, John F. Kennedy Space Center, Research Reports: 1990 NASA(ASEE Summer Faculty Fellowship Program; p 169-196
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    Microwave conductivity of laser ablated YBaCuO superconducting films and its relation to microstrip transmission line (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The discovery of high temperature superconductor oxides has raised the possibility of a new class of millimeter and microwave devices operating at temperatures considerably higher than liquid helium temperatures. Therefore, materials properties such as conductivity, current density, and sheet resistance as a function of temperature and frequency, possible anisotropies, moisture absorption, thermal expansion, and others, have to be well characterized and understood. The millimeter wave response was studied of laser ablated YBa2Cu3O(7-x)/LaAlO3 thin films as a function of temperature and frequency. In particular, the evaluation of their microwave conductivity was emphasized, since knowledge of this parameter provides a basis for the derivation of other relevant properties of these superconducting oxides, and for using them in the fabrication of actual passive circuits. The microwave conductivity for these films was measured at frequencies from 26.5 to 40.0 GHz, in the temperature range from 20 to 300 K. The values of the conductivity are obtained from the millimeter wave power transmitted through the films, using a two fluid model.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA, Goddard Space Flight Center, AMSAHTS 1990: Advances in Materials Science and Applications of High Temperature Superconductors; p 78-81
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  • 95
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    Electronic state and superconductivity of YBa2Cu3-xO7-y (M=Al,Zn and Sn) systems (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A series of YBa2Cu(3-x)MxO(7-y) (M=Al,Zn and Sn) single phase samples were prepared, and the measurements of the crystal structure, oxygen content, electric resistivity, thermoelectric power, Mossbauer spectrum, XPS and superconductivity were performed. The experimental results of X ray powder diffraction, Mossbauer spectrum and oxygen content show that the Zn(2+) and the Al(3+) occupy the Cu(2) site in Cu-O planes and the Cu(1) site in Cu-O chains respectively, but the Sn(4+) occupies both the Cu(1) sites. As regards the properties in superconducting state, both the Zn(2+) and the Al(3+) depress T(sub c) strongly, but the Sn(4+) does not. As for the electronic transport properties in normal state, the system doped by Al(3+) displays a rapid increase of resistivity and some electron localization-like effects, and the thermoelectric power enhances obviously; the series contained Zn(2+) almost shows no changes of electric resistivity but the sign of the thermoelectric power is reversed. Other results are given and briefly discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA, Goddard Space Flight Center, AMSAHTS 1990: Advances in Materials Science and Applications of High Temperature Superconductors; p 76
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  • 96
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    High-temperature electronics (1990)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Aeropropulsion 1987; p 233-241
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    Design of QMF (Quadrature Mirror Filter) in spatial domain and edge encoding (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Simoncelli and Adelson have extended the one dimensional Quadrature Mirror Filter (QMF) to two dimensions with hexagon symmetry and three dimensional spatio-temporal extensions with rhombic-duodecahedray symmetry. Jain and Crochiere presented an excellent QMF design technique in the time domain. It is proposed to extend the design of a two dimensional QMF over a rectangular lattice in the spatial domain based primarily on the extension of the idea of Jain and Crochiere. In addition, the design will investigate the use of two dimensional Z-transformations. Since this proposed QMF is intended for the applications in image processing, all the important and interesting engineering issues will be addressed throughout the development phase. The design of a two dimensional QMF is discussed. The motivation is to achieve an extremely high data compression ratio. It is entirely possible to achieve dramatic results when pattern recognition techniques are employed. The final goal is the demonstration of extremely high data compression ratios using NASA pictures.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Hampton Univ., NASA/American Society for Engineering Ed; Hampton Univ., NASA(
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  • 98
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    Natural vacuum electronics (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The ambient natural vacuum of space is proposed as a basis for electron valves. Each valve is an electron controlling structure similiar to a vacuum tube that is operated without a vacuum sustaining envelope. The natural vacuum electron valves discussed offer a viable substitute for solid state devices. The natural vacuum valve is highly resistant to ionizing radiation, system generated electromagnetic pulse, current transients, and direct exposure to space conditions.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA. Lewis Research Center, Vision-21: Space Travel for the Next Millennium; p 477-484
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  • 99
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    Thermal/vacuum vs. thermal atmospheric testing of space flight electronic assemblies (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: For space flight hardware, the thermal vacuum environmental test is the best test of a system's flight worthiness. Substituting an atmospheric pressure thermal test for a thermal/vacuum test can effectively reduce piece part temperatures by 20 C or more, even for low power density designs. Similar reductions in test effectiveness can also result from improper assembly level T/V test boundary conditions. The net result of these changes may reduce the effective test temperatures to the point where there is zero or negative margin over the flight thermal environment.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA, Goddard Space Flight Center, 16th Space Simulation Conference Confirming Spaceworthiness Into the Next Millennium; p 344-356
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  • 100
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    NASA developments in solid state power amplifiers (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Over the last ten years, NASA has undertaken an extensive program aimed at development of solid state power amplifiers for space applications. Historically, the program may be divided into three phases. The first efforts were carried out in support of the advanced communications technology satellite (ACTS) program, which is developing an experimental version of a Ka-band commercial communications system. These first amplifiers attempted to use hybrid technology. The second phase was still targeted at ACTS frequencies, but concentrated on monolithic implementations, while the current, third phase, is a monolithic effort that focusses on frequencies appropriate for other NASA programs and stresses amplifier efficiency. The topics covered include: (1) 20 GHz hybrid amplifiers; (2) 20 GHz monolithic MESFET power amplifiers; (3) Texas Instruments' (TI) 20 GHz variable power amplifier; (4) TI 20 GHz high power amplifier; (5) high efficiency monolithic power amplifiers; (6) GHz high efficiency variable power amplifier; (7) TI 32 GHz monolithic power amplifier performance; (8) design goals for Hughes' 32 GHz variable power amplifier; and (9) performance goals for Hughes' pseudomorphic 60 GHz power amplifier.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Solid State Technology Branch of NASA Lewis Research Center Second Annual Digest, June 1989 - June 1990; p 3-10
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