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withers

HR: 1340h
AN: SH43A-1807 Poster
TI: An exploratory survey of the attenuation of radio signals by the ionosphere of Mars
AU: *Withers, P
EM: withers@bu.edu
AF: Boston University, Boston, MA, USA
AB: A radio signal is attenuated as it passes through a planetary ionosphere. This attenuation depends on the radio frequency, the electron-neutral collision frequency, and the vertical profile of electron density. Thus the attenuation varies with changes in ionospheric conditions. In particular, extreme solar events, such as intense solar flares or solar energetic particle events, that increase ionospheric electron densities at altitudes below 100 km may cause significantly enhanced attentuation. Such attenuation has the potential to degrade the performance of radio communications and navigation systems at Mars. It can also disrupt observations by the MARSIS topside radar sounder on Mars Express. We have developed theoretical expressions for the attenuation caused by a layer of ionospheric plasma. In this presentation, we shall use these results to explore how the attenuation depends on radio frequency and layer altitude, electron density, and width. We shall focus on three plasma layers - the M1 layer produced at 100 km by solar soft X-rays, the meteoric layer produced at 85 km by meteoroid ablation, and a potential layer at 35 km that theorists have predicted is caused by precipitating energetic particles. We shall also report on the implications for understanding surface reflection blackouts that afflict the MARSIS instrument for periods of days to weeks after solar energetic particle events.
DE: [6225] PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Mars
SC: SPA-Solar and Heliospheric Physics (SH)
MN: 2010 Fall Meeting