Multipoint Analysis of Source Regions of EMIC Waves by THEMIS Spacecraft

Abstract:

Electromagnetic Ion Cyclotron (EMIC) Waves play an important role in the dynamics of the outer radiation belt as they can interact mainly with the MeV electrons and scatter them into loss-cone rapidly. These waves are generated by temperature anisotropy () of energetic protons and seen at mainly dusk-side plasmapause (around MLAT). They are observed in the range of Pc1 and Pc2 (0.1-5 Hz) and below the proton gyrofrequency. Provided the presence of temperature anisotropy, these waves are mostly generated at the equator, where minimum magnetic field is typical. These can be observed at any L-shell at different latitudes due to their propagation along the magnetic field. We present observations of EMIC waves by THEMIS A, D, and E in the outer magnetosphere, where THEMIS E is closest to the equator and THEMIS A and D are around 2000 km separated from THEMIS E. Three almost identical events are observed around 12 mins apart by the three spacecraft. This configuration of THEMIS spacecraft gives an excellent platform for finding the source regions of EMIC waves by analyzing how the EMIC events are observed simultaneously by the three spacecraft. These EMIC waves are in proton band, where we clearly observe rising tones emissions with subpackets which are left-handed polarized and wave normal angle ≤ 30^o. We present here the Poynting flux analysis to understand the direction of the energy flow mechanism and to locate the common source regions of EMIC waves.