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Electric Mars: The first direct measurement of an upper limit for the Martian “polar wind” electric potential
Author(s) -
Collinson Glyn,
Mitchell David,
Glocer Alex,
Grebowsky Joseph,
Peterson W. K.,
Connerney Jack,
Andersson Laila,
Espley Jared,
Mazelle Christian,
Sauvaud JeanAndré,
Fedorov Andrei,
Ma Yingjuan,
Bougher Steven,
Lillis Robert,
Ergun Robert,
Jakosky Bruce
Publication year - 2015
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 - 10.1002/2015gl065084
Subject(s) - mars exploration program , ionosphere , atmospheric escape , solar wind , martian , ambipolar diffusion , atmosphere of mars , polar wind , electric field , physics , atmospheric sciences , geophysics , electric potential , exosphere , outflow , astrobiology , environmental science , meteorology , electron , plasma , ion , interplanetary magnetic field , voltage , quantum mechanics
An important mechanism in the generation of polar wind outflow is the ambipolar electric potential which assists ions in overcoming gravity and is a key mechanism for Terrestrial ionospheric escape. At Mars, open field lines are not confined to the poles, and outflow of ionospheric electrons is observed far into the tail. It has thus been hypothesized that a similar electric potential may be present at Mars, contributing to global ionospheric loss. However, no direct measurements of this potential have been made. In this pilot study, we examine photoelectron spectra measured by the Solar Wind Electron Analyzer instrument on the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) Mars Scout to put an initial upper bound on the total potential drop in the ionosphere of Mars ofΦ ♂≾ ⊥2 V , with the possibility of a further ≾ 4.5 V potential drop above this in the magnetotail. If the total potential drop was close to the upper limit, then strong outflows of major ionospheric species (H + , O + , andO 2 + ) would be expected. However, if most of the potential drop is confined below the spacecraft, as expected by current theory, then such a potential would not be sufficient on its own to accelerateO 2 +to escape velocities, but would be sufficient for lighter ions. However, any potential would contribute to atmospheric loss through the enhancement of Jeans escape.