Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns

J. Cui, Y. T. Cao, X. S. Wu, S. S. Xu, Roger Yelle, S. Stone, E. Vigren, N. J.T. Edberg, C. L. Shen, F. He, Y. Wei

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Abstract

Combining the Mars Atmosphere and Volatile Evolution (MAVEN) measurements of atmospheric neutral and ion densities, electron temperature, and energetic electron intensity, we perform the first quantitative evaluation of local ionization balance in the nightside Martian upper atmosphere, a condition with the electron impact ionization (EI) of CO2 exactly balanced by the dissociative recombination (DR) of ambient ions. The data accumulated during two MAVEN Deep Dip (DD) campaigns are included: DD6 on the deep nightside with a periapsis solar zenith angle (SZA) of 165°, and DD3 close to the dawn terminator with a periapsis SZA of 110°. With the electron temperatures at low altitudes corrected for an instrumental effect pertaining to the MAVEN Langmuir Probe and Waves, a statistical agreement between the EI and DR rates is suggested by the data below 140 km during DD6 and below 180 km during DD3, implying that electron precipitation is responsible for the nightside Martian ionosphere under these circumstances and extra sources are not required. In contrast, a substantial enhancement in EI over DR is observed at higher altitudes during both campaigns, which we interpret as a signature of plasma escape down the tail.

Original languageEnglish (US)
Article numberL12
JournalAstrophysical Journal Letters
Volume876
Issue number1
DOIs
StatePublished - May 1 2019

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Mars atmosphere
Martian atmosphere
upper atmosphere
Mars
ionization
electron impact
electron
atmosphere
zenith
recombination
zenith angle
electron energy
electron flux density
electron precipitation
low altitude
electrostatic probes
high altitude
ionospheres
escape
ion

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns. / Cui, J.; Cao, Y. T.; Wu, X. S.; Xu, S. S.; Yelle, Roger; Stone, S.; Vigren, E.; Edberg, N. J.T.; Shen, C. L.; He, F.; Wei, Y.

In: Astrophysical Journal Letters, Vol. 876, No. 1, L12, 01.05.2019.

Research output: Contribution to journalArticle

Cui, J, Cao, YT, Wu, XS, Xu, SS, Yelle, R, Stone, S, Vigren, E, Edberg, NJT, Shen, CL, He, F & Wei, Y 2019, 'Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns', Astrophysical Journal Letters, vol. 876, no. 1, L12. https://doi.org/10.3847/2041-8213/ab1b34
Cui, J. ; Cao, Y. T. ; Wu, X. S. ; Xu, S. S. ; Yelle, Roger ; Stone, S. ; Vigren, E. ; Edberg, N. J.T. ; Shen, C. L. ; He, F. ; Wei, Y. / Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns. In: Astrophysical Journal Letters. 2019 ; Vol. 876, No. 1.
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