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Simulation of dispersionless injections and drift echoes of energetic electrons associated with substorms
Author(s) -
Li Xinlin,
Baker D. N.,
Temerin M.,
Reeves G. D.,
Belian R. D.
Publication year - 1998
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 - 10.1029/1998gl900001
Subject(s) - physics , electron , substorm , computational physics , electric field , magnetic field , population , van allen radiation belt , plasmoid , test particle , particle acceleration , field line , pitch angle , astrophysics , atomic physics , magnetosphere , geophysics , magnetic reconnection , classical mechanics , nuclear physics , demography , quantum mechanics , sociology
The term “dispersionless injection” refers to a class of events which show simultaneous enhancement (injection) of electrons and ions with different energies usually seen at or near geosynchronous orbit. We show that dispersionless injections can be understood as a consequence of changes in the electric and magnetic fields by modeling an electron injection event observed early on January 10, 1997 by means of a test‐particle simulation. The model background magnetic field is a basic dipole field made asymmetrical by a compressed dayside and a weakened nightside. The transient fields are modeled with only one component of the electric field which is westward and a consistent magnetic field. These fields are used to model the major features of a dipolarization process during a substorm onset. We follow the electrons using a relativistic guiding center code. Our simulation results, with an initial kappa electron energy flux spectrum, reproduce the observed electron injection and subsequent drift echoes and show that the energization of injected electrons is mainly due to betatron acceleration of the preexisting electron population at larger radial distances in the magnetotail by transient fields.