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Plasma Clouds and Snowplows: Bulk Plasma Escape from Mars Observed by MAVENWe present initial Mars Atmosphere and Volatile EvolutioN (MAVEN) observations and preliminary interpretation of bulk plasma loss from Mars. MAVEN particle and field measurements show that planetary heavy ions derived from the Martian atmosphere can escape in the form of discrete coherent structures or "clouds." The ions in these clouds are unmagnetized or weakly magnetized, have velocities well above the escape speed, and lie directly downstream from magnetic field amplifications, suggesting a "snowplow" effect. This postulated escape process, similar to that successfully used to explain the dynamics of active gas releases in the solar wind and terrestrial magnetosheath, relies on momentum transfer from the shocked solar wind protons to the planetary heavy ions, with the electrons and magnetic field acting as intermediaries. Fluxes of planetary ions on the order of 10(exp 7)/sq cm/s can escape by this process, and if it operates regularly, it could contribute 10-20% of the current ion escape from Mars.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Halekas, J. S.
(Iowa Univ. Iowa City, IA, United States)
Brain, D. A.
(Colorado Univ. Boulder, CO, United States)
Ruhunusiri, S.
(Iowa Univ. Iowa City, IA, United States)
McFadden, J. P.
(California Univ. Berkeley, CA, United States)
Mitchell, D. L.
(California Univ. Berkeley, CA, United States)
Mazelle, C.
(Institut de Recherche en Astrophysique et Planetologie (UMR) Toulouse, France)
Connerney, J. E. P.
(Adnet Systems, Inc. Greenbelt, MD, United States)
Harada, Y.
(California Univ. Berkeley, CA, United States)
Hara, T.
(California Univ. Berkeley, CA, United States)
Espley, J. R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
DiBraccio, G. A.
(Universities Space Research Association Greenbelt, MD, United States)
Jakosky, B. M.
(Colorado Univ. Boulder, CO, United States)
Date Acquired
March 17, 2017
Publication Date
February 25, 2016
Publication Information
Publication: Geophysical Research Letters
Volume: 43
Issue: 4
ISSN: 0094-8276
Subject Category
Plasma Physics
Report/Patent Number
Funding Number(s)
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