Oblique reflections in the Mars Express MARSIS data set:stable density structures in the Martian ionosphere

Andrews, David and Andre, Mats and Opgenoorth, Hermann and Edberg, Niklas and Dieval, Catherine and Duru, Firdevs and Gurnett, Donald and Morgan, David and Witasse, Olivier (2014) Oblique reflections in the Mars Express MARSIS data set:stable density structures in the Martian ionosphere. Journal of Geophysical Research: Space Physics, 119 (5). pp. 3944-3960. ISSN 2169-9402

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Abstract

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the European Space Agency's Mars Express (MEX) spacecraft routinely detects evidence of localized plasma density structures in the Martian dayside ionosphere. Such structures, likely taking the form of spatially extended elevations in the plasma density at a given altitude, give rise to oblique reflections in the Active Ionospheric Sounder data. These structures are likely related to the highly varied Martian crustal magnetic field. In this study we use the polar orbit of MEX to investigate the repeatability of the ionospheric structures producing these anomalous reflections, examining data taken in sequences of multiple orbits which pass over the same regions of the Martian surface under similar solar illuminations, within intervals lasting tens of days. Presenting three such examples, or case studies, we show for the first time that these oblique reflections are often incredibly stable, indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters. The visibility, or lack thereof, of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory. We show that, within these examples, oblique reflections are generally detected whenever the spacecraft passes over regions of intense near-radial crustal magnetic fields (i.e., with a “cusp-like” configuration). The apparent stability of these structures is an important feature that must be accounted for in models of their origin.

Item Type:
Journal Article
Journal or Publication Title:
Journal of Geophysical Research: Space Physics
ID Code:
76671
Deposited By:
Deposited On:
13 Nov 2015 15:20
Refereed?:
Yes
Published?:
Published
Last Modified:
05 Dec 2020 03:02