A statistic study of EMIC wave properties associated with and without injections using multi-point in-situ satellite observations.
Abstract
Using 47 months of observations from the Van Allen Probes (RBSP) and Geostationary Operational Environmental Satellite (GOES-13 and -15), we identified EMIC wave events observed by RBSP and energetic particle injections simultaneously observed by GOES-13 and -15 on the nighttime. We investigated EMIC wave properties of the dominant wave band inside and outside the plasmasphere associated with and without injections. We found that He+ EMIC waves have higher wave power than H+ EMIC waves. In addition, He+ EMIC waves inside the plasmasphere associated with injections are predominantly left-hand polarized and the wave normal angles are smaller at the dusk sector where the peak occurrence rates are. On the other hand, the left-hand polarized He+ EMIC waves without injection are observed with scattered wave powers in all MLT over wider |MLAT| regions. Near the magnetic equator with |MLAT|<10°, H+ EMIC waves outside the plasmasphere exhibit linearly polarized with lower wave normal angles compared to higher latitudes. We also found that polarization sense at all category have dependences on |MLAT| and wave normal angle, indicating waves propagate to higher magnetic latitudes. From these observations, we suggest that EMIC waves are generated within |MLAT|<10°, but the wave source regions inside the plasmasphere during quiet geomagnetic conditions can extent above 10° |MLAT|. The overlap regions between cold plasma and hot injected or ring current plasma are the preferred conditions for He+ EMIC wave generation and enhanced wave power in the inner magnetosphere. Different major drivers, such as magnetospheric compressions by solar wind dynamic pressure, would contribute more to generating H+ EMIC waves outside the plsamasphere with linearly polarized waves and lower wave normal angle on the dayside.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM12A..08J
- Keywords:
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- 2730 Magnetosphere: inner;
- MAGNETOSPHERIC PHYSICSDE: 2774 Radiation belts;
- MAGNETOSPHERIC PHYSICSDE: 7845 Particle acceleration;
- SPACE PLASMA PHYSICSDE: 7867 Wave/particle interactions;
- SPACE PLASMA PHYSICS