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Cluster observations of velocity space‐restricted ion distributions near the plasma sheet
Author(s) -
Wilber M.,
Lee E.,
Parks G. K.,
Meziane K.,
Carlson C. W.,
McFadden J. P.,
Rème H.,
Dandouras I.,
Sauvaud J.A.,
Bosqued J.M.,
Kistler L.,
Möbius E.,
McCarthy M.,
Korth A.,
Klecker B.,
BavassanoCattaneo M.B.,
Lundin R.,
Lucek E.
Publication year - 2004
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 - 10.1029/2004gl020265
Subject(s) - physics , plasma sheet , current sheet , ion , cluster (spacecraft) , plasma , perpendicular , transverse plane , computational physics , atomic physics , range (aeronautics) , space physics , astrophysics , geophysics , magnetosphere , geometry , nuclear physics , magnetohydrodynamics , materials science , mathematics , structural engineering , quantum mechanics , computer science , engineering , composite material , programming language
We present Cluster ion observations obtained at 18 R E in the magnetotail on 1 October 2001. According to a recent analysis, the quartet encountered a reconnection region and a tailward‐moving neutral line. We examine in detail selected 3‐D ion distributions, which through much of the hour following 0925 UT were non‐gyrotropic. B ‐perpendicular slices of velocity space showed crescent‐shaped regions. Occupied gyrophases were consistent over a wide range of parallel velocities, stable over time, and occurred unaccompanied by strong ion gyrofrequency waves. We interpret these observations as signatures of remote sensing near sharp particle gradients. In this view, distributions obtained simultaneously while Cluster straddled the current sheet are simply explained. Additionally, the computed first moments can have large transverse ( × B ) components (, a unit boundary normal), without net plasma transport. We infer separate O + layers above and below the current sheet.