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Evidence for Day-to-Night Ion Transport at Low Solar Activity in the Venus Pre-Dawn IonospherePeriapsis of the Pioneer Venus spacecraft dropped below 180 km on August 28, 1992 near midnight, and 42 orbits of low altitude data at moderately low solar activity in the pre-dawn sector were obtained before contact was lost to the spacecraft in October, 1992. Through a combination of analysis of data from the PV orbiter ion mass spectrometer (OIMS) and modeling, we consider here what can be learned about the relative importance of plasma transport from the dayside and electron precipitation in maintaining the nightside ionosphere during the re-entry period. In particular, we examine here the atomic ion density profiles. We compute the average peak density of O(+) as a function of solar zenith angle and determine what fluxes of atomic ions or precipitating electrons would be necessary to produce those values. We then compare model calculations of the ion densities to those observed during the re-entry period. We find that the low solar activity nightside ionosphere shows evidence of significant day-to-night plasma transport.
Document ID
19990038324
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Brannon, J. F.
(State Univ. of New York Stony Brook, NY United States)
Fox, J. L.
(State Univ. of New York Stony Brook, NY United States)
Porter, H. S.
(Furman Univ. Greenville, SC United States)
Date Acquired
August 19, 2013
Publication Date
December 14, 1993
Publication Information
Publication: Geophysical Research Letters. Selected Papers on Pioneer Venus Orbiter: Entry Phase
Volume: 20
Issue: 23
Subject Category
Lunar And Planetary Exploration
Report/Patent Number
Paper 93GL02422
Funding Number(s)
CONTRACT_GRANT: NAGw-2958
Distribution Limits
Public
Copyright
Public Use Permitted.
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