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Sources of electron pitch angle anisotropy in the magnetotail plasma sheet
Author(s) -
Walsh Andrew P.,
Fazakerley A. N.,
Forsyth C.,
Owen C. J.,
Taylor M. G. G. T.,
Rae I. J.
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/jgra.50553
Subject(s) - magnetosheath , plasma sheet , pitch angle , electron , physics , ionosphere , anisotropy , magnetosphere , current sheet , whistler , flux (metallurgy) , plasma , computational physics , atomic physics , interplanetary magnetic field , geophysics , solar wind , magnetopause , materials science , optics , magnetohydrodynamics , quantum mechanics , metallurgy
We survey the properties of electron pitch angle distributions in the magnetotail plasma sheet at a distance between 15 and 19 R E from the Earth, using data from the Plasma Electron and Current Experiment (PEACE) instrument. We limit our survey to those pitch angle distributions measured when the interplanetary magnetic field (IMF) had been steadily northward or steadily southward for the previous 3 h. We find that, at sub‐keV energies, the plasma sheet electron pitch angle distribution has an anisotropy such that there is a higher differential energy flux of electrons in the (anti‐) field‐aligned directions. Fitting the measured pitch angle distributions with both a single and two component kappa distribution reveals that this anisotropy is the result of the presence of a second, cold, component of electrons that is observed more often than not, and occurs during both the northward and southward IMF intervals. We present evidence that suggests the cold electron component has an ionospheric, rather than magnetosheath, source and is linked to the large‐scale field‐aligned current systems that couple the magnetosphere and ionosphere.