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The location of the dayside ionopause of Venus: Pioneer Venus Orbiter Magnetometer observations
Author(s) -
Elphic R. C.,
Russell C. T.,
Slavin J. A.,
Brace L. H.,
Nagy A. F.
Publication year - 1980
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl007i008p00561
Subject(s) - atmosphere of venus , venus , solar wind , solar zenith angle , ionosphere , physics , orbiter , geophysics , zenith , coronal mass ejection , atmospheric sciences , geodesy , geology , astrobiology , astronomy , plasma , quantum mechanics
The location of the dayside Venus ionopause, as observed by the Pioneer Venus Orbiter, is shown to depend on the magnetic pressure in the shocked, highly compressed solar wind plasma just outside the ionopause. Assuming a balance exclusively between this external magnetic pressure and internal ionospheric thermal pressure, invariance of ionospheric conditions, and an isothermal ionosphere, it is possible to determine pressure scale heights for various solar zenith angle intervals. These scale heights yield ionospheric temperatures which agree with direct measurements obtained independently. Not surprisingly, the average ionopause altitude is higher near the terminator, where the average external magnetic pressure is lower. The near‐terminator ionopause has much greater positional variability than that at lower solar zenith angles; this appears to be due principally to concomitant variations in the external magnetic pressure, presumably related to solar wind pressure changes.