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Conjugate observations of quasiperiodic emissions by the Cluster, Van Allen Probes, and THEMIS spacecraft
Author(s) -
Němec F.,
Hospodarsky G.,
Pickett J. S.,
Santolík O.,
Kurth W. S.,
Kletzing C.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja022774
Subject(s) - spacecraft , physics , quasiperiodic function , plasmasphere , van allen probes , magnetosphere , earth's magnetic field , modulation (music) , geophysics , van allen radiation belt , astrophysics , astronomy , magnetic field , acoustics , quantum mechanics , condensed matter physics
We present results of a detailed analysis of two electromagnetic wave events observed in the inner magnetosphere at frequencies of a few kilohertz, which exhibit a quasiperiodic (QP) time modulation of the wave intensity. The events were observed by the Cluster and Van Allen Probes spacecraft and in one event also by the THEMIS E spacecraft. The spacecraft were significantly separated in magnetic local time, demonstrating a huge azimuthal extent of the events. Geomagnetic conditions at the times of the observations were very quiet, and the events occurred inside the plasmasphere. The modulation period observed by the Van Allen Probes and THEMIS E spacecraft (duskside) was in both events about twice larger than the modulation period observed by the Cluster spacecraft (dawnside). Moreover, individual QP elements occur about 15 s earlier on THEMIS E than on Van Allen Probes, which might be related to a finite propagation speed of a modulating ULF wave.