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  • Other Sources  (867)
  • COMPUTER PROGRAMMING AND SOFTWARE  (401)
  • MECHANICAL ENGINEERING  (242)
  • SOLAR PHYSICS
  • 1990-1994  (867)
  • 1970-1974
  • 1993  (867)
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  • Other Sources  (867)
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  • 1990-1994  (867)
  • 1970-1974
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  • 1
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    Contrast of faculae near the disk center and solar variability (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We analyze simultaneous, or near-simultaneous, coregistered, digital, photometric images of solar photospheric intensity and line-of-sight magnetic field. Images were made with the Lockheed tunable filter instrument at the Swedish Solar Observatory, La Palma, with the video spectra-spectroheliograph system at the San Fernando Observatory and with the new NASA spectromagnetograph at the National Solar Observatory at Kitt Peak. We study the disk center contrasts of small magnetic elements. While active region faculae are dark at disk center quiet Sun network features are bright. The populations of magnetic field elements that make up these two kinds of features are quite different. Different contrast center-limb functions must be used when estimating their irradiance or luminosity contributions. The disk center contrasts of active region faculae are colar dependent and indicate a depth effect related to the H(-) opacity of the facular atmopshere. This results is important for calibration of monochromatic observations of faculae to bolometric irradiance fluctuations. We emphasize the value of cooperative observations among installations whose differing strengths are complementary.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A11; p. 18,911-18,918
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  • 2
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    Rotational effects on convection simulated at different latitudes (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We simulate numerically convection inside the solar convection zone under the influence of rotation at different latitudes. The computational domain is a small rectangular box with stress-free upper and lower boundaries, and with periodicity assumed in the lateral directions. We study the transport of angular momentum, which is important for the generation of differential rotation. The sign and the latitudinal dependence of the horizontal Reynolds stress component turn out to be in good agreement with correlation measurements of sunspot proper motions and with predictions from the theory of the Lambda effect. We also investigate the other components of the Reynolds stress as well as the eddy heat flux tensor, both of which are needed in mean field models of differential rotation.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 267; 1; p. 265-274.
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  • 3
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    The Consolidated Planning and Scheduling System for Space Transportation and Space Station operations - Successful development experience (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: In 1992, NASA made the decision to evolve a Consolidated Planning System (CPS) by adding the Space Transportation System (STS) requirements to the Space Station Freedom (SSF) planning software. This paper describes this evolutionary process, which began with a series of six-month design-build-test cycles, using a domain-independent architecture and a set of developmental tools known as the Advanced Scheduling Environment. It is shown that, during these tests, the CPS could be used at multiple organizational levels of planning and for integrating schedules from geographically distributed (including international) planning environments. The potential for using the CPS for other planning and scheduling tasks in the SSF program is being currently examined.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: IAF PAPER 93-408 , IAF, International Astronautical Congress; Oct 16, 1993 - Oct 22, 1993; Graz; Austria|; 7 p.
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  • 4
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    Signatures of shock drivers in the solar wind and their dependence on the solar source location (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Solar wind and energetic ion observations following 40 interplanetary shocks with well-established solar source locations have been examined in order to determine whether signatures characteristic of the coronal material forming the shock driver are present. The signatures considered include magnetic-field-aligned bidirectional ion flows observed by the ISEE 3 and IMP 8 spacecraft; bidirectional solar wind electron heat fluxes; solar wind plasma proton and electron temperature depressions; low-beta plasma; enhanced, low-variance magnetic fields; and energetic ion depressions. Several shock driver signatures are commonly observed following shocks originating from within about 50 deg of central meridian, and are generally absent for other events. We conclude that shock drivers generally extend up to about 100 deg in longitude, centered on the solar source longitude. Since shocks from central meridian events are not usually associated with all the shock driver signatures examined, the absence of a driver cannot be confirmed from consideration of one of these signatures alone. We also find evidence that a few bidirectional energetic ion and solar wind electron heat flux events following shocks (in particular from far eastern sources) may occur on open field lines outside of shock drivers.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A9; p. 15,295-15,304.
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  • 5
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    The differential emission measure of nested hot and cool magnetic loops (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The detailed thermal structure of the magnetized solar transition region, as measured by its differential emission measure (DEM(T)), is poorly known. Building on the fact that the solar surface is strongly magnetized and thereby structured, proposals have been made that envision a significant lower-temperature contribution to the energy balance from (ion) heat flux across an arcade of different temperature loops. In this paper, we describe a self-consistent 2D MHD simulation, which includes the full thermal effects of parallel stability and anisotropic conduction, of a nested-loop model of the thermal and magnetic structure of the transition region. We then demonstrate that the predicted DEM agrees with observations in the conceptually elusive T less than 10 exp 5 K regime.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 147; 1; p. 199-202.
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  • 6
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    Evolving directions in NASA's planetary rover requirements and technology (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The evolution of NASA's planning for planetary rovers (that is robotic vehicles which may be deployed on planetary bodies for exploration, science analysis, and construction) and some of the technology that was developed to achieve the desired capabilities is reviewed. The program is comprised of a variety of vehicle sizes and types in order to accommodate a range of potential user needs. This includes vehicles whose weight spans a few kilograms to several thousand kilograms; whose locomotion is implemented using wheels, tracks, and legs; and whose payloads vary from microinstruments to large scale assemblies for construction. Robotic vehicles and their associated control systems, developed in the late 1980's as part of a proposed Mars Rover Sample Return (MRSR) mission, are described. Goals suggested at the time for such a MRSR mission included navigating for one to two years across hundreds of kilometers of Martian surface; traversing a diversity of rugged, unknown terrain; collecting and analyzing a variety of samples; and bringing back selected samples to the lander for return to Earth. Current plans (considerably more modest) which have evolved both from technological 'lessons learned' in the previous period, and modified aspirations of NASA missions are presented. Some of the demonstrated capabilities of the developed machines and the technologies which made these capabilities possible are described.
    Keywords: MECHANICAL ENGINEERING
    Type: CNES, Missions, Technologies, and Design of Planetary Mobile Vehicles; p 443-454
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  • 7
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    Are the 1986-1988 changes in solar free-oscillation frequency splitting significant? (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The solar normal-mode splitting coefficients deduced from Big Bear Solar Observatory (BBSO) data differ between 1986 and 1988; inversions for equatorial rotation are slower at depth and faster near the surface in 1988 than in 1986. The significance of the change has been disputed. The data sets overlap for five splitting coefficients (a(j))super 5 sub j = 1 associated with 710 multiplets. On the assumption that rotation rate varies smoothly with radius, both data sets are satisfied by the same rotation model at all colatitudes except near 30-40 deg and near 70 deg (and at their southern hemisphere reflections 140-150 deg and 110 deg). The evidence for equatorial change is weak. Nonparametric tests show a significant offset in the magnitudes of a(1), a(2), and a(4), and of linear combinations sensitive to rotation at colatitudes of 60-80 deg (and 120 deg). Nonparametric tests show significant radial trends in the changes to a(2), a(4), and (less significantly) a(5). There is strong anticorrelation between a(2) and a(4), a(1) and a(3), and a(3) and a(5), suggesting that the estimates are not independent. Individual coefficients a(j) show more evidence for change than do 'physical' linear combinations, adding weight to this hypothesis. Some of the changes in splitting might be related to solar activity, which changed most near colatitude 70 deg from 1986 to 1988.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 415; 1; p. 376-382.
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  • 8
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    Dynamics of the solar chromosphere. I - Long-period network oscillations (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We analyze differences in solar oscillations between the chromospheric network and internetwork regions from a 1 hr sequence of spectrograms of a quiet region near disk center. The spectrograms contain Ca II H, Ca I 422.7 nm, and various Fe I blends in the Ca II H wing. They permit vertical tracing of oscillations throughout the photosphere and into the low chromosphere. We find that the rms amplitude of Ca II H line center Doppler fluctuations is about 1.5 km/s for both network and internetwork, but that the character of the oscillations differs markedly in these two regions. Within internetwork areas the chromospheric velocity power spectrum is dominated by oscillations with frequencies at and above the acoustic cutoff frequency. They are well correlated with the oscillations in the underlying photosphere, but they are much reduced in the network. In contrast, the network Ca II H line center velocity and intensity power spectra are dominated by low-frequency oscillations with periods of 5-20 min. Their signature is much clearer in our Ca II H line center measurements than in previously used diagnostics which are contaminated by signals from deeper layers. We find that these long-period oscillations are not correlated with underlying photospheric disturbances, and we discuss their nature.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 414; 1; p. 345-356.
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  • 9
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    Elemental abundances in the upper solar atmosphere of quiet and coronal hole regions (Te is approximately equal to 4.3 x 10 exp 5 K) (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Detailed examination of the sun's upper atmosphere reveals that elemental abundances vary between different solar regions. Some solar regions exhibit the well-established photospheric abundances, while in other regions the abundances of some elements diverge from photospheric by an order of magnitude, and perhaps even more. Elemental abundances in the solar wind (SW) are also different from elemental abundances in the photosphere. It is postulated that elemental abundances in the SW reflect the elemental abundances of their place of origin near the solar surface. The solar surface is covered, predominantly, by quiet and coronal hole regions. In this paper we measure the intensities of limb-brightening rings over quiet and coronal hole regions in lines of Mg VI and Ne VI (Te is approximately equal to 4.3 x 10 exp 5 K) and determine the relative elemental abundances of the features producing the rings. The rings are formed by a plasma component occupying only a small fraction of the immediate volume above the solar surface.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 414; 1; p. 381-388.
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  • 10
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    VLA-BATSE observations of an intense solar decimetric and hard X-ray burst (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: We discuss observations of a multiply impulsive solar burst that was detected simultaneously by the VLA at 20 and 90 cm and by the Burst and Transient Experiment (BATSE) at hard X-ray wavelengths. The flare-associated 20 cm emission consists of two groups of bursts about 4 min apart. Hard X-ray emission above 25 keV was detected during both groups of bursts, while 90 cm bursts occurred only during the second and more intense group. VLA snapshot maps at intervals of 1.7 s reveal that the 20 cm burst originates within a relatively compact source located above the east limb at a height of roughly 1.8 x 10 exp 10 cm. The 90 cm burst is more extended and lies at a height of roughly 2.2 x 10 exp 10 cm. The similarity of the time profiles in the two spectral domains suggests a common injection of energetic electrons, while the time delays are consistent with the travel times of electrons which propagate from the chromosphere to the sites of the coronal radio bursts. We find that the VLA emission is probably the type III or type IV radiation of electrons trapped in large coronal loops, and that plasma radiation, rather than gyrosynchrotron emission, can explain it.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 413; 2; p. 798-810.
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