The Martian Photoelectron Boundary as Seen by MAVEN

P Garnier; M Steckiewicz; C Mazelle; S Xu; D Mitchell; M. K. G Holmberg; J. S Halekas; L Andersson; D. A Brain; J. E. P Connerney; J. R Espley; R. J Lillis; J. G Luhmann; J.‐A Sauvaud; B. M Jakosky

doi:10.1002/2017JA024497

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The Martian Photoelectron Boundary as Seen by MAVEN

Journal article

Peer reviewed

The Martian Photoelectron Boundary as Seen by MAVEN

P Garnier, M Steckiewicz, C Mazelle, S Xu, D Mitchell, M. K. G Holmberg, J. S Halekas, L Andersson, D. A Brain, J. E. P Connerney, …

Journal of geophysical research. Space physics, Vol.122(10), pp.10,472-10,485

10/2017

DOI: 10.1002/2017JA024497

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Abstract

Photoelectron peaks in the 20–30 eV energy range are commonly observed in the planetary atmospheres, produced by the intense photoionization from solar 30.4 nm photons. At Mars, these photoelectrons are known to escape the planet down its tail, making them tracers for the atmospheric escape. Furthermore, their presence or absence allow to define the so‐called photoelectron boundary (PEB), which separates the photoelectron dominated ionosphere from the external environment. We provide here a detailed statistical analysis of the location and properties of the PEB based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) electron and magnetic field data obtained from September 2014 to May 2016 (including 1696 PEB crossings). The PEB appears as mostly sensitive to the solar wind dynamic and crustal fields pressures. Its variable altitude thus leads to a variable wake cross section for escape (up to ∼+50%), which is important for deriving escape rates. The PEB is not always sharp and is characterized on average by the following: a magnetic field topology typical for the end of magnetic pileup region above it, more field‐aligned fluxes above than below, and a clear change of the altitude slopes of both electron fluxes and total density (that appears different from the ionopause). The PEB thus appears as a transition region between two plasma and fields configurations determined by the draping topology of the interplanetary magnetic field around Mars and much influenced by the crustal field sources below, whose dynamics also impacts the estimated escape rate of ionospheric plasma. Key Points We determined the influence of the main driving parameters on the altitude of the photoelectron boundary (PEB) We identified clear plasma and magnetic field characteristics of the PEB and discuss its nature with respect to the ionopause We show how the PEB dynamics modifies the tail cross section used for estimating the photoelectrons (and associated ions) escape rate

ionosphere

Mars

plasma boundary

plasma escape

solar wind interaction

Details

Title: Subtitle: The Martian Photoelectron Boundary as Seen by MAVEN
Creators: P Garnier - Université de Toulouse
M Steckiewicz - Université de Toulouse
C Mazelle - Université de Toulouse
S Xu - University of California, Berkeley
D Mitchell - University of California, Berkeley
M. K. G Holmberg - Université de Toulouse
J. S Halekas - Goddard Space Flight Center
L Andersson - University of Colorado Boulder
D. A Brain - University of Colorado Boulder
J. E. P Connerney - University of Iowa
J. R Espley - University of Iowa
R. J Lillis - University of California, Berkeley
J. G Luhmann - University of California, Berkeley
J.‐A Sauvaud - IRAP, Université de Toulouse, CNRS, UPS, CNES
B. M Jakosky - University of Colorado Boulder
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.122(10), pp.10,472-10,485
DOI: 10.1002/2017JA024497
ISSN: 2169-9380
eISSN: 2169-9402
Number of pages: 14
Grant note: French space agency CNES
Language: English
Date published: 10/2017
Academic Unit: Physics and Astronomy
Record Identifier: 9984199748702771

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