An observational study of the nightside ionospheres of Mars and Venus with radio occultation methods

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA10p17095· OSTI ID:5029483

Zhang, M H.G. ^[1]; Luhmann, J G ^[2]; Kliore, A J ^[3]

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1. Austrian Academy of Sciences, Graz (Austria)
2. Univ. of California, Los Angeles (United States)
3. Jet Propulsion Lab., Pasadena, CA (United States)

An analysis of Mars and Venus nightside electron density profiles obtained with radio occultation methods shows how the nightside ionospheres of both planets vary with solar zenith angle. From previous studies it is known that the dayside peak electron densities at Mars and Venus show a basic similarity in that they both exhibit Chapman layer-like behavior. In contrast, the peak altitudes at mars behave like an ideal Chapman layer on the dayside, whereas the altitude of the peak at Venus is fairly constant up to the terminator. The effect of major dust storms can also be seen in the peak altitudes at Mars. All Venus nightside electron density profiles show a distinct main peak for both solar minimum and maximum, whereas many profiles from the nightside of Mars do not show any peak at all. This suggests that the electron density in the Mars nightside ionosphere is frequently too low to be detected by radio occultation. On the Pioneer Venus orbiter, disappearing ionospheres were observed near solar maximum in the in-situ data when the solar wind dynamic pressure was exceptionally high. This condition occurs because the high solar wind dynamic pressure decreases the altitude of the ionopause near the terminator below {approximately}250 km, thus reducing the normal nightward transport of dayside ionospheric plasma. On the basis of the Venus observations, one might predict that if a positive correlation of nightside peak density with dynamic pressure was found, it could mean that transport from the dayside is the only significant source for the nightside ionosphere of Mars. The lack of a correlation would imply that the precipitation source at Mars is quite variable.

• OSTI ID: 5029483
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:A10; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MARS PLANET
PLANETARY IONOSPHERES
ELECTRON DENSITY
VENUS PLANET
CHARGED-PARTICLE TRANSPORT
CORRELATIONS
DUSTS
MEASURING METHODS
PLASMA PRESSURE
SOLAR WIND
VARIATIONS
PLANETS
RADIATION TRANSPORT
SOLAR ACTIVITY
640107* - Astrophysics & Cosmology- Planetary Phenomena