Journal article
Steep, transient density gradients in the Martian ionosphere similar to the ionopause at Venus
Journal of Geophysical Research: Space Physics, Vol.114(A12), A12310
12/2009
DOI: 10.1029/2009JA014711
Abstract
With the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the Mars Express (MEX) spacecraft, the electron density can be measured by two methods: from the excitation of local plasma oscillations and from remote sounding. A study of the local electron density versus time for 1664 orbits revealed that in 132 orbits very sharp gradients in the electron density occurred that are similar to the ionopause boundary commonly observed at Venus. In 40 of these cases, remote sounding data have also confirmed identical locations of steep ionopause‐like density gradients. Measurements from the Analyzer of Space Plasma and Energetic Atoms (ASPERA‐3) electron spectrometer and ion mass analyzer instruments (also on Mars Express) verify that these sharp decreases in the electron density occur somewhere between the end of the region where ionospheric photoelectrons are dominant and the magnetosheath. Combined studies of the two experiments reveal that the steep density gradients define a boundary where the magnetic fields change from open to closed. This study shows that, although the individual cases are from a wide range of altitudes, the average altitude of the boundary as a function of solar zenith angle is almost constant. The average altitude is approximately 500 km up to solar zenith angles of 60°, after which it shows a slight increase. The average thickness of the boundary is about 22 km according to remote sounding measurements. The altitude of the steep gradients shows an increase at locations with strong crustal magnetic fields.
Details
- Title: Subtitle
- Steep, transient density gradients in the Martian ionosphere similar to the ionopause at Venus
- Creators
- F Duru - University of IowaD. A Gurnett - University of IowaR. A Frahm - Southwest Research InstituteJ. D Winningham - Southwest Research InstituteD. D Morgan - University of IowaG. G Howes - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of Geophysical Research: Space Physics, Vol.114(A12), A12310
- DOI
- 10.1029/2009JA014711
- ISSN
- 0148-0227
- eISSN
- 2156-2202
- Number of pages
- 17
- Language
- English
- Date published
- 12/2009
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199751402771
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