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MARSIS remote sounding of localized density structures in the dayside Martian ionosphere: A study of controlling parameters
Author(s) -
Diéval C.,
Andrews D. J.,
Morgan D. D.,
Brain D. A.,
Gurnett D. A.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021486
Subject(s) - ionosphere , martian , ionospheric sounding , geology , geophysics , mars exploration program , depth sounding , solar wind , atmospheric sciences , magnetic field , geodesy , physics , astrobiology , oceanography , quantum mechanics
Abstract Enhanced topside electron densities in the dayside Martian ionosphere have been repetitively observed in areas of near‐radial crustal magnetic fields, for periods of tens of days, indicating their long‐term spatial and temporal stability despite changing solar wind conditions. We perform a statistical study of these density structures using the ionospheric mode of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. We estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere. The apex of the density structures often lies higher than the surrounding ionosphere (median vertical extent of 18 km), which indicates upwellings. These structures are much wider than they are high, with latitudinal scales of several degrees. The radar reflector regions are observed above both moderate and strong magnetic anomalies, and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity (oblique to vertical fields), which happen to be regions where the field lines are open part of the time. The majority of the density structures occur in regions where ionospheric plasma is dominant, indicating closed field regions shielded from shocked solar wind plasma.