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Spatial dependence of electromagnetic ion cyclotron waves triggered by solar wind dynamic pressure enhancements
Author(s) -
Cho J.H.,
Lee D.Y.,
Noh S.J.,
Kim H.,
Choi C. R.,
Lee J.,
Hwang J.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023827
Subject(s) - magnetosphere , plasmasphere , physics , geophysics , computational physics , cyclotron , local time , noon , solar wind , astrophysics , ion , atmospheric sciences , plasma , nuclear physics , statistics , mathematics , quantum mechanics
In this paper, using the multisatellite (the Van Allen Probes and two GOES satellites) observations in the inner magnetosphere, we examine two electromagnetic ion cyclotron (EMIC) wave events that are triggered by P dyn enhancements under prolonged northward interplanetary magnetic field quiet time preconditions. For both events, the impact of enhanced P dyn causes EMIC waves at multiple points. However, we find a strong spatial dependence that EMIC waves due to enhanced P dyn impact can occur at multiple points (likely globally but not necessarily everywhere) but with different wave properties. For Event 1, three satellites situated at a nearly same dawnside zone but at slightly different L shells see occurrence of EMIC waves but in different frequencies relative to local ion gyrofrequencies and with different polarizations. These waves are found inside or at the outer edge of the plasmasphere. Another satellite near noon observes no dramatic EMIC wave despite the strongest magnetic compression there. For Event 2, the four satellites are situated at widely separated magnetic local time zones when they see occurrence of EMIC waves. They are again found at different frequencies relative to local ion gyrofrequencies with different polarizations and all outside the plasmasphere. We propose two possible explanations that (i) if triggered by enhanced P dyn impact, details of ion cyclotron instability growth can be sensitive to local plasma conditions related to background proton distributions, and (ii) there can be preexisting waves with a specific spatial distribution, which determines occurrence and specific properties of EMIC waves depending on satellite's relative position after an enhanced P dyn arrives.