Thermal structure and major ion composition of the Venus ionosphere: First RPA results from Venus orbiter

W. C. Knudsen, K. Spenner, R. C. Whitten, J. R. Spreiter, K. L. Miller, V. Novak

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Thermal plasma quantities measured by the retarding potential analyzer (RPA) are, together with companion Pioneer Venus measurements, the first in situ measurements of the Venus ionosphere. High ionospheric ion and electron temperatures imply significant solar wind heating of the ionosphere. Comparison of the measured altitude profiles of the dominant ions with an initial model indicates that the ionosphere is close to diffusive equilibrium. The ionopause height was observed to vary from 400 to 1000 kilometers in early orbits. The ionospheric particle pressure at the ionopause is apparently balanced at a solar zenith angle of about 70° by the magnetic field pressure with little contribution from energetic solar wind particles. The measured ratio of ionospheric scale height to ionopause radius is consistent with that inferred from previously measured bow shock positions.

Original languageEnglish
Pages (from-to)757-763
Number of pages7
JournalScience
Volume203
Issue number4382
DOIs
StatePublished - 1979

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