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MESSENGER Observations of Fast Plasma Flows in Mercury's Magnetotail
Author(s) -
Dewey Ryan M.,
Raines Jim M.,
Sun Weijie,
Slavin James A.,
Poh Gangkai
Publication year - 2018
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 - 10.1029/2018gl079056
Subject(s) - substorm , plasma , plasma sheet , physics , mercury (programming language) , spacecraft , magnetic field , asymmetry , spectrometer , geophysics , computational physics , magnetosphere , astronomy , optics , nuclear physics , computer science , quantum mechanics , programming language
We present the first observation of fast plasma flows in Mercury's magnetotail. Mercury experiences substorm activity phenomenologically similar to Earth's; however, field‐of‐view limitations of the Fast Imaging Plasma Spectrometer (FIPS) prevent the instrument from detecting fast flows in the plasma sheet. Although FIPS measures incomplete plasma distributions, subsonic flows impart an asymmetry on the partial plasma distribution, even if the flow directions are outside the field of view. We combine FIPS observations from 387 intervals containing magnetic field dipolarizations to mitigate these instrument limitations. By taking advantage of variations in spacecraft pointing during these intervals, we construct composite plasma distributions from which mean flows are determined. We find that dipolarizations at Mercury are embedded within fast sunward flows with an averaged speed of ~300 km/s compared to a typical background flow of ~50 km/s.