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MAVEN observations of dayside peak electron densities in the ionosphere of Mars
Author(s) -
Vogt Marissa F.,
Withers Paul,
Fallows Kathryn,
Andersson Laila,
Girazian Zachary,
Mahaffy Paul R.,
Benna Mehdi,
Elrod Meredith K.,
Connerney John E. P.,
Espley Jared R.,
Eparvier Frank G.,
Jakosky Bruce M.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023473
Subject(s) - solar zenith angle , ionosphere , electron density , mars exploration program , altitude (triangle) , martian , zenith , atmosphere of mars , electron , physics , atmospheric sciences , scale height , atmosphere (unit) , electron temperature , geophysics , computational physics , astrophysics , astronomy , optics , meteorology , geometry , mathematics , quantum mechanics
The peak electron density in the dayside Martian ionosphere is a valuable diagnostic of the state of the ionosphere. Its dependence on factors like the solar zenith angle, ionizing solar irradiance, neutral scale height, and electron temperature has been well studied. The Mars Atmosphere and Volatile EvolutioN spacecraft's September 2015 “deep dip” orbits, in which the orbital periapsis was lowered to ~125 km, provided the first opportunity since Viking to sample in situ a complete dayside electron density profile including the main peak. Here we present peak electron density measurements from 37 deep dip orbits and describe conditions at the altitude of the main peak, including the electron temperature and composition of the ionosphere and neutral atmosphere. We find that the dependence of the peak electron density and the altitude of the main peak on solar zenith angle are well described by analytical photochemical theory. Additionally, we find that the electron temperatures at the main peak display a dependence on solar zenith angle that is consistent with the observed variability in the peak electron density. Several peak density measurements were made in regions of large crustal magnetic field, but there is no clear evidence that the crustal magnetic field strength influences the peak electron density, peak altitude, or electron temperature. Finally, we find that the fractional abundance of O 2 + and CO 2 + at the peak altitude is variable but that the two species together consistently represent ~95% of the total ion density.