TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 2), pp. 105-112, 2012

Neutral wind effects on ion outflow at Mars

L. Andersson1 and R. E. Ergun1,2

1Laboratory of Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, United States
2Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80302, United States

(Received February 9, 2011; Revised May 18, 2011; Accepted June 23, 2011; Online published March 8, 2012)

Abstract: This paper evaluates the influence of neutral winds on ions using the CAPIT (Combined Atmospheric Photochemistry and Ion Tracking) code, which includes ionospheric photochemistry and plasma wave energization. Based on two different wind profiles, ion outflow is, to first order, not sensitive to neutral winds. However, the ion density profiles are clearly affected by neutral winds at the exobase. For example, the direction of a strong neutral wind will dramatically change the location of the highest ion densities. This finding suggests that strongly varying neutral winds at the exobase complicate the analysis of in-situ observations. To evaluate dynamic effects of the different magnetic field configurations, crustal fields are included in the simulation domain. The outflow of O2+ ions is the most dynamic, partly because the photochemical production is almost a factor of two larger than the photochemical loss so loss to space is important (for other ions, this ratio is closer to one and loss to space is small compared to photochemical production). Since the photochemical production rate of O2+ is relatively slow, it takes time to replenish O2+ that is lost to space, so loss to space over long periods should be relatively constant.
Key words: Double layer, aurora, acceleration.

Corresponding author E-mail: Laila.Andersson@lasp.colorado.edu

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