Journal article
Ionospheric Irregularities at Mars Probed by MARSIS Topside Sounding
Journal of geophysical research. Space physics, Vol.123(1), pp.1018-1030
01/2018
DOI: 10.1002/2017JA024913
Abstract
The upper ionosphere of Mars contains a variety of perturbations driven by solar wind forcing from above and upward propagating atmospheric waves from below. Here we explore the global distribution and variability of ionospheric irregularities around the exobase at Mars by analyzing topside sounding data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Mars Express. As irregular structure gives rise to off‐vertical echoes with excess propagation time, the diffuseness of ionospheric echo traces can be used as a diagnostic tool for perturbed reflection surfaces. The observed properties of diffuse echoes above unmagnetized regions suggest that ionospheric irregularities with horizontal wavelengths of tens to hundreds of kilometers are particularly enhanced in the winter hemisphere and at high solar zenith angles. Given the known inverse dependence of neutral gravity wave amplitudes on the background atmospheric temperature, the ionospheric irregularities probed by MARSIS are most likely associated with plasma perturbations driven by atmospheric gravity waves. Though extreme events with unusually diffuse echoes are more frequently observed for high solar wind dynamic pressures during some time intervals, the vast majority of the diffuse echo events are unaffected by varying solar wind conditions, implying limited influence of solar wind forcing on the generation of ionospheric irregularities. Combination of remote and in situ measurements of ionospheric irregularities would offer the opportunity for a better understanding of the ionospheric dynamics at Mars.
Key Points
MARSIS observes diffuse ionospheric echoes, which are indicative of ionospheric irregularities around the exobase at Mars
The winter hemisphere and high solar zenith angles are strongly favored for observations of the diffuse echoes
The ionospheric irregularities are driven primarily by atmospheric gravity waves and secondarily by solar wind forcing
Details
- Title: Subtitle
- Ionospheric Irregularities at Mars Probed by MARSIS Topside Sounding
- Creators
- Y Harada - University of IowaD. A Gurnett - University of IowaA. J Kopf - University of IowaJ. S Halekas - University of IowaS Ruhunusiri - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.123(1), pp.1018-1030
- DOI
- 10.1002/2017JA024913
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 13
- Grant note
- NASA (1560641)
- Language
- English
- Date published
- 01/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199806502771
Metrics
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