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  • 1
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    Response of earth and Venus ionospheres to corotating solar wind stream of 3 July 1979 (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Corotating solar wind stream interactions are examined for the earth and Venus in light of data from the plasma detectors aboard ISEE-3, the Pioneer Venus Orbiter (PVO), and Helios-A, as well as in situ ion composition measurements taken by the mass spectrometers aboard the PVO and Atmosphere Explorer-E spacecraft. During May-July 1979, a sequence of distinct, recurrent coronal regions developed at the sun; their analysis indicates a corresponding sequence of corotating streams. Although the planetary environments are distinctly different, it is noted that pronounced and analogous ionospheric responses to the stream passage were observed at both the earth and Venus. The response to the intercepted stream is consistent with independent investigations showing the importance of the variability of the solar wind momentum flux in the solar wind-ionosphere interaction at both planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon and Planets (ISSN 0167-9295); 32; 275-290
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  • 2
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    Physics of the interaction of the solar wind with the ionosphere of Venus - Flow/field models (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Venus deflects incident solar wind by means of thermal and magnetic pressure, both of which are produced by ionospheric currents that are in turn driven by pressure gradients and electric fields induced in the ionosphere by the flowing magnetized solar wind plasma. The ionospheric currents connect across the ionopause into the ionosheath region, and close on, and behind, the bow shock. The computed ionospheric plasma velocity distribution is found to be spatially asymmetric, with the fastest flow velocities lying perpendicular to the ionospheric magnetic fields. Computations also indicate that the ionosphere is susceptible to an MHD shear instability whose extent and location is a function of external solar wind conditions. The present Venus ionosphere model compares well with in situ Pioneer Venus Orbiter observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 3
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    Corotating interplanetary streams and associated ionospheric disturbances at Venus and earth (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: During the summer of 1979, solar corona structure was such that a sequence of recurrent regions produced a corresponding sequence of corotating solar wind streams with pronounced downstream signatures. One of these stream events passed earth on July 3 and was observed later at Venus late on July 11th, with similar characteristics. Corresponding in situ measurements at earth from the Atmospheric Explorer-E satellite and at Venus from the Pioneer Venus Orbiter are examined for evidence of comparable perturbations of the planetary ionospheres. The passage of the stream shock front is found to be associated with pronounced fluctuations in n(O+) which appear as pronounced local depletion of ion concentrations in both ionospheres. The ionosphere disturbances appear to be closely associated with large variations in the solar wind momentum flux. The implied local ionospheric depletions observed at each planet are interpreted to be the consequence of plasma redistribution, rather than actual depletions of plasma.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 4
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    Internet-Working Satellite and Local Exchange Networks for Personal Communications Applications (1993)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The demand for personal communications services has shown unprecedented growth, and the next decade and beyond promise an era in which the needs for ubiquitous, transparent and personalized access to information will continue to expand in both scale and scope.
    Keywords: Communications and Radar
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  • 5
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    On the nature of the interaction of the Jovian magnetosphere with the icy Galilean satellites (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The effects of plasma and micrometeoroid bombardment of each satellite are considered in the case of interactions between the Jovian magnetosphere and Europa, Ganymede, and Callisto, in an attempt to understand the influences of these exogenic processes on the surface properties of each of the three moons. Sublimated and sputtered H2O results in a net O2 atmosphere on each of the three moons, and the effectiveness of such an atmosphere in preventing the Jovian plasma from reaching each satellite surface is considered for a variety of magnetospheric conditions. Also studied are the effects of possible satellite magnetic field magnitude and orientation, in order to estimate satellite magnetosphere properties, and the orbits of charged micrometeroids in the Jupiter magnetosphere, in order to determine the relative flux of these particles over the satellite surfaces.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; June 1
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  • 6
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    Ultraviolet observations of the Cygnus Loop (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The analysis of IUE observations of a filament on the western edge of the Cygnus Loop yields a shock velocity of about 130 km/sec, significantly higher than the velocity estimated from the optical spectrum. This velocity together with the high forbidden O III/H-beta ratio reported by Miller (1974) indicates that much of the hydrogen recombination region predicted by steady flow shock models is absent. This situation may occur because this part of the supernova remnant is in the shell-formation phase that accompanies the transition from the adiabatic to the snowplow phase or because the observed filament is a recently shocked cloud.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 238
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  • 7
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    The onset and development of Kelvin-Helmholtz instability at the Venus ionopause (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The paper investigates the Kelvin-Helmholtz instability at the Venus ionopause resulting from the flow of the (shocked) solar wind tangential to the ionopause for the case where the interplanetary field is oriented normal to the direction of flow. It is found that gravity stabilizes the long wavelength perturbations, and the finite thickness of the boundary layer stabilizes short wavelength modes. The magnetic 'gyroviscosity' due to finite Larmor radius effects either destabilizes the boundary or stabilizes it according to whether the solar wind electric field points away from or toward the ionosphere. For solar wind and ionosphere plasma parameters consistent with Pioneer Venus observations, it is found that the instabilities with the greatest growth rates (shortest growth times) have wavelengths of 50-150 km and growth times of 0.5 to several seconds. In addition, it is found how distortion of the ionopause by Kelvin-Helmholtz instability might lead to the formation of magnetic 'flux ropes' inside the ionosphere as well as ionospheric 'bubbles' embedded in the solar wind.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 8
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    The dynamics of the Venus ionosphere. II - The effects of the time scale of the solar wind dynamic pressure variations (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effects on the upper dayside Venus ionosphere of a slow increase in solar wind dynamic pressure are simulated numerically with a one-dimensional (spherically symmetric) Lagrangian hydrodynamical code. The simulation is started with an extended ionosphere in pressure equilibrium with the solar wind at the ionopause. The pressure at the ionopause is gradually increased to five times the initial pressure with rise times of 5, 15, and 30 min. It is found that, for rise times greater than about 10 min, the compression of the ionopause is nearly adiabatic, with the ionopause moving downward at velocities of approximately 1-2 km/sec until it reaches a maximally compressed state, at which time the motion reverses. For short rise times the compression produces a shock wave similar to that occurring in the case of a sudden increase in pressure. The global implications of these processes are discussed within the context of Pioneer Venus observations and future theoretical work on this problem is outlined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 9
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    An upper limit to the low-energy X-ray flux from beta Persei (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A region of the sky including the binary system Algol (beta Persei) was observed with a one-dimensional, grazing-incidence X-ray telescope sensitive in the energy range from 0.5 to 4.0 keV. No statistically significant flux was detected above that attributable to the diffuse and cosmic-ray induced backgrounds. This result allows an upper limit of .02 billionths of an erg/sq cm sec keV at 1.6 keV to be set for the X-ray emission from this source at the epoch of observation. The absence of detectable low-energy X-rays is consistent with a thermal radio source, on condition that no flares occurred at the time of observation.
    Keywords: ASTRONOMY
    Type: Astrophysical Letters; 16; 1975
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  • 10
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    A graphite crystal polarimeter for stellar X-ray astronomy. (1972)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The first crystal X-ray polarimeter to be used for X-ray astronomy is described. Polarization is measured by modulation of the X rays diffracted at an average 45 deg glancing angle from large, curved graphite crystal panels as these rotate about an axis parallel to the incident X-ray flux. Arrangement of the crystal panels, the design of the detector, and the signal-processing circuitry were optimized to minimize systematic effects produced by off-axis pointing of the rocket and cosmic ray induced events. The in-flight performance of the instrument in relation to the observed background signal is discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 43; July 197
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