Viking 1 electron observations at Mars

Journal Article · Mon Jul 01 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA00317· OSTI ID:5316855

Johnson, F S; Hanson, W B ^[1]

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1. Univ. of Texas, Richardson (USA)

The Viking retarding potential analyzer (RPA) flown to Mars in 1976 had negative retarding potential sweeps in addition to the positive ion sweeps. An analysis of the electron mode sweeps made in Viking 1 above the ionosphere is presented here. A spectrum covering the range 0 to {minus}78 V was recorded in 1 s. and electron observations were made at intervals of 4 or 8 s. The derived electron concentrations and temperatures in the solar wind are lower than the generally accepted values, but the maximum electron pressures derived above the ionosphere are about as high as can be expected for generally accepted solar wind values. Except in the highly variable or turbulent region from about 2500 km down to 500 km, the scans show a high degree of consistency from scan to scan. The initial concentrations near 15,000 km were slightly less than 1 cm{sup {minus}3} characterized by a temperature of about 40,000 K, plus what is interpreted as a backstreaming component from the planetary shock of about 0.1 cm{sup {minus}3} at about 250,000 K. The shock appeared to be quasi-parallel, as there was no evidence of a sharp transition anywhere near the expected shock position; it appears that the shock transition region extended from about 3,500 down to 850 km. The hottest region was near 850 km, where there is clear evidence of an electron component too hot for the RPA to measure; it produced abundant secondary emission and is assumed to be characterized by energies of about 200 eV so as to be efficient in the production of secondaries. The electron concentrations there averaged about 30 cm{sup {minus}3}.

• OSTI ID: 5316855
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A7, Issue A7; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MARS PLANET
PLANETARY IONOSPHERES
SOLAR WIND
INTERACTIONS
ALTITUDE
CALCULATION METHODS
DATA ANALYSIS
ELECTRON DENSITY
ELECTRON SPECTRA
ELECTRON TEMPERATURE
MEASURING INSTRUMENTS
SHOCK WAVES
VIKING SPACE PROBES
PLANETS
SOLAR ACTIVITY
SPACE VEHICLES
SPECTRA
VEHICLES
640107* - Astrophysics & Cosmology- Planetary Phenomena