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Transient layers in the topside ionosphere of Mars
Author(s) -
Kopf A. J.,
Gurnett D. A.,
Morgan D. D.,
Kirchner D. L.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl034948
Subject(s) - ionosphere , mars exploration program , geology , geophysics , solar zenith angle , depth sounding , solar wind , zenith , radar , atmospheric tide , atmosphere of mars , martian , atmospheric sciences , geodesy , physics , thermosphere , astrobiology , plasma , aerospace engineering , oceanography , quantum mechanics , engineering
Radar soundings from the MARSIS instrument on board the Mars Express spacecraft have shown that distinct layers can occur in the topside ionosphere of Mars, well above the main photo‐ionization layer. These layers appear as cusps, or sometimes steps, in plots of the time delay as a function of frequency. Usually only one topside layer is observed, typically at altitudes from 180 to 240 km. However, occasionally an additional layer occurs at even higher altitudes. The layers are transient features and are present about 60% of the time near the subsolar point, decreasing with increasing solar zenith angle to less than 5% at the terminator and the nightside. The transient nature of the layers suggests that they are produced by a dynamical process, most likely involving an interaction with the solar wind in the upper levels of the ionosphere.