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Stochastic and direct acceleration mechanisms in the Earth's magnetotail
Author(s) -
Perri S.,
Greco A.,
Zimbardo G.
Publication year - 2009
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 - 10.1029/2008gl036619
Subject(s) - physics , fermi acceleration , acceleration , particle acceleration , electric field , computational physics , test particle , electromagnetic field , current sheet , range (aeronautics) , ion , charged particle , atomic physics , quantum electrodynamics , magnetic field , classical mechanics , magnetohydrodynamics , quantum mechanics , materials science , composite material
Ion beams with energies of the order of several tens of keV are frequently observed in the Earth's magnetotail. Here we consider two possible acceleration mechanisms, the cross tail electric field E y and the stochastic acceleration due to the electromagnetic fluctuations present in the magnetotail. Electromagnetic perturbations are generated by random oscillating “clouds” moving in the x − y plane. A test particle simulation has been performed in order to reproduce the interaction between protons and electromagnetic fluctuations and the constant dawn‐dusk electric field, E y , in the magnetotail current sheet. Protons are accelerated via a stochastic Fermi‐like process and, by varying the features of the electromagnetic fluctuations, the combined effect of E y and of the moving clouds can explain the typical energy range of ion observations from 20 to 100 keV, and the characteristic acceleration times of several minutes.