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Comparative aeronomy: Molecular ionospheres at Earth and Mars
Author(s) -
Mendillo Michael,
Trovato Jeffrey,
Narvaez Clara,
Mayyasi Majd,
Moore Luke,
Vogt Marissa F.,
Fallows Kathryn,
Withers Paul,
Martinis Carlos
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023097
Subject(s) - aeronomy , ionosphere , ion , extreme ultraviolet , dissociative recombination , electron density , mars exploration program , ionization , atomic physics , atmosphere (unit) , plasma , physics , electron , astrobiology , materials science , atmospheric sciences , chemistry , astronomy , optics , meteorology , recombination , laser , biochemistry , quantum mechanics , gene
The ionospheres in our solar system vary not only in their electron densities but also in the dominance of atomic versus molecular ions at their altitudes of peak plasma density. With the exception of Earth's F layer composed of atomic oxygen ions and electrons, all other planets have their peak ionospheric layers composed of molecular ions and electrons embedded in a dense neutral atmosphere. At Mars, both of its ionospheric layers have molecular ions, with the M 1 layer at a lower altitude than the more robust M 2 layer above it. The terrestrial ionosphere has a prominent region of molecular ions (the E layer) below the dominant F layer. In this paper, we explore the production and loss of molecular ion layers observed under the same solar irradiance conditions at Mars and Earth. We compare observations of M 1 and M 2 electron densities with terrestrial ionosonde data for the peak densities of the E and F layers during low, moderate, and high solar flux conditions. The subsolar peak densities of molecular ion layers have high correlations at each planet, as well as between planets, even though they are produced by separate portions of the solar spectrum. We use photochemical‐equilibrium theory for layers produced by soft X‐rays ( M 1 and E ) versus the M 2 layer produced by extreme ultraviolet (EUV) to identify the key parameters that cause similarities and differences. The yield of our comparative study points to the roles of secondary ionization and temperature‐dependent plasma recombination rates as areas most in need of further study at each planet.