Statistical characteristics of EMIC wave‐driven relativistic electron precipitation with observations of POES satellites: Revisit

Abstract

Electromagnetic ion cyclotron (EMIC) waves play an important role in the magnetospheric dynamics and can scatter relativistic electrons in the outer radiation belt into the loss cone leading to the rapid loss of relativistic electrons. In this paper, we present characteristics of EMIC wave-driven relativistic electron precipitation (REP) with observations of six Polar Orbiting Environmental Satellites (POES). Based on the simultaneity between spikes in the P1 0°(Ep = 30 keV-80 keV) and P6 0°(Ee > 1 MeV) channels, in comparison with the criterion of Carson et al. (2013), we improve the algorithm and make it stricter. A total of 436,286 individual half orbits between 1998 and 2010 are inspected by this algorithm. The majority of selected events are observed at L values within the outer radiation belt (3 < L < 7) and more common in 1800-2200 magnetic local time. The distribution of normalized events follows the location of plasmapause contracting toward lower L value with the decrease of the Dst index, implying a strong link between detected events and the plasmapause. The cluster of normalized events moves to later afternoon sector where the peak occurrence of plasmaspheric plumes is located during geomagnetic storms. It is suggested that there is a connection between plasmaspheric plumes and detected events. Corresponding to the peak of event occurrence in 2003, solar wind dynamic pressure has a same peak. In addition, the minimum values of them are coincident. These results indicate that the increase of the solar wind dynamic pressure enhances the likelihood of EMIC wave-driven relativistic electron precipitation.

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

“…[]]. Evidence has also been presented indicating that solar wind dynamic pressure influences relativistic electron precipitation events, driven by EMIC waves, more than geomagnetic activity [ Wang et al ., ].…”

EMIC waves covering wide L shells: MMS and Van Allen Probes observations

“…EMIC waves have attracted much attention for several decades since these waves could play important roles in terrestrial magnetosphere dynamics, such as energizing cold particles through Landau or/and cyclotron resonance [e.g., Horne and Thorne , ; Zhang et al , , ; Yuan et al , , ] and precipitating ring current ions through pitch angle scattering [e.g., Yuan et al , , ]. Moreover, according to diffusion coefficients calculated from quasi‐linear theory [ Summers, ; Albert , ], EMIC waves are thought to make significant contributions to the loss of radiation belt electrons [ Yuan et al , ; Wang et al , ; Usanova et al , ].…”

Statistical characteristics of EMIC waves: Van Allen Probe observations

“…Active Magnetospheric Particle Tracer Explorers (AMPTE) CCE observations show that EMIC waves mainly occur between 11:00 and 18:00 MLT [ Anderson et al ., , ]. Inferred from the events of simultaneous precipitation of relativistic electrons and ring current ions observed by the NOAA POES satellites, EMIC waves are found to be generally located at the dusk to midnight sectors [ Z. Wang et al ., ]. Although some statistical studies claim that the occurrence rate of the EMIC waves in the inner magnetosphere is limited, just several percent [ Min et al ., ; Usanova et al ., ; Meredith et al ., ], one shortcoming of the previous statistical studies is that the spacecraft such as Time History of Events and Macroscale Interactions during Substorms (THEMIS) and CRRES spent limited time in the inner magnetosphere, especially in lower L shells.…”