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Influence of the Interplanetary Convective Electric Field on the Distribution of Heavy Pickup Ions Around Mars
Author(s) -
Johnson B. C.,
Liemohn M. W.,
Fränz M.,
Ramstad R.,
Stenberg Wieser G.,
Nilsson H.
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024463
Subject(s) - solar wind , magnetosphere , mars exploration program , physics , electric field , polar wind , plume , geophysics , martian , interplanetary magnetic field , interplanetary spaceflight , computational physics , northern hemisphere , atmospheric sciences , astrobiology , magnetic field , meteorology , quantum mechanics
Abstract This study obtains a statistical representation of 2–15 keV heavy ions outside of the Martian‐induced magnetosphere and depicts their organization by the solar wind convective electric field ( E SW ). The overlap in the lifetime of Mars Global Surveyor (MGS) and Mars Express (MEX) provides a period of nearly three years during which magnetometer data from MGS can be used to estimate the direction of E SW in order to better interpret MEX ion data. In this paper we use MGS estimates of E SW to express MEX ion measurements in Mars‐Sun‐Electric field (MSE) coordinates. A new methodological technique used in this study is the limitation of the analysis to a particular instrument mode for which the overlap between proton contamination and plume observations is rare. This allows for confident energetic heavy ion identification outside the induced magnetosphere boundary. On the dayside, we observe high count rates of 2–15 keV heavy ions more frequently in the + E SW hemisphere (+ Z MSE ) than in the − E SW hemisphere, but on the nightside the reverse asymmetry was found. The results are consistent with planetary origin ions being picked up by the solar wind convective electric field. Though a field of view hole hinders quantification of plume fluxes and velocity space, this new energetic heavy ion identification technique means that Mars Express should prove useful in expanding the time period available to assess general plume loss variation with drivers.