EMIC Wave Events During the Four GEM QARBM Challenge Intervals

Abstract

This paper presents observations of electromagnetic ion cyclotron (EMIC) waves from multiple data sources during the four Geospace Environment Modeling challenge events in 2013 selected by the Geospace Environment Modeling Quantitative Assessment of Radiation Belt Modeling focus group: 17 and 18 March (stormtime enhancement), 31 May to 2 June (stormtime dropout), 19 and 20 September (nonstorm enhancement), and 23–25 September (nonstorm dropout). Observations include EMIC wave data from the Van Allen Probes, Geostationary Operational Environmental Satellite, and Time History of Events and Macroscale Interactions during Substorms spacecraft in the near‐equatorial magnetosphere and from several arrays of ground‐based search coil magnetometers worldwide, as well as localized ring current proton precipitation data from low‐altitude Polar Operational Environmental Satellite spacecraft. Each of these data sets provides only limited spatial coverage, but their combination shows consistent occurrence patterns and reveals some events that would not be identified as significant using near‐equatorial spacecraft alone. Relativistic and ultrarelativistic electron flux observations, phase space density data, and pitch angle distributions based on data from the Relativistic Electron‐Proton Telescope and Magnetic Electron Ion Spectrometer instruments on the Van Allen Probes during these events show two cases during which EMIC waves are likely to have played an important role in causing major flux dropouts of ultrarelativistic electrons, particularly near L* ~4.0. In three other cases, identifiable smaller and more short‐lived dropouts appeared, and in five other cases, these waves evidently had little or no effect.

Rapid Outer Radiation Belt Flux Dropouts and Fast Acceleration During the March 2015 and 2013 Storms: The Role of Ultra‐Low Frequency Wave Transport From a Dynamic Outer Boundary

“…In addition, the simulation results shown in Figure are consistent with the results presented by Engebretson et al (), who showed that during the March 2013 storm no EMIC waves were observed either in space or on the ground which were intense enough inside L < 4 to account for the observed fast flux dropout. However, statistical studies indicate that EMIC waves can occur over a narrow range of L‐shells and local times making detection of the waves difficult (see e.g., Saikin et al, and Usanova et al, ).…”

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

“…Many recent studies are dedicated to the loss they cause to ultrarelativistic electrons (e.g., Thorne & Kennel, ; Albert, ; Jordanova et al, ; Miyoshi et al, ; Rodger et al, , Rodger et al, ; Li et al, , 2014; Usanova et al, , ; Kersten et al, ; Blum et al, ; Clilverd et al, ; Woodger et al, , ; Colpitts et al, ; Shprits et al, , , , ; Hendry et al, , ; Zhang et al, ; Aseev et al, ; Drozdov, Shprits, Usanova, et al, ; Capannolo et al, , ; Denton et al, ; Qin et al, ), themselves related to the complex location and duration of these waves. EMIC waves are discrete electromagnetic emissions in multiple frequency bands (e.g., Saikin et al, ), which are observed across a large region of geospace (e.g., Saikin et al, ), including the ring current and the plasmasphere, dayside plumes, and the outer dayside magnetosphere (Engebretson et al, ; Engebretson et al, ; Engebretson et al, ; Tetrick et al, ). When EMIC emissions occur, they often spread over one (or a few) MLT sectors, which limits their effect.…”

The Effect of Plasma Boundaries on the Dynamic Evolution of Relativistic Radiation Belt Electrons

“…We also show the results of the simulations without EMIC waves for 500‐keV and 4‐MeV electrons in the supporting material and compare them with satellite observations. In general, without taking EMIC waves into account, our simulations reproduce the dynamic evolution of electrons at energies of 500 and 900 keV well but overestimated the flux of electrons with energies of 4 MeV in Events 1, 2, 3, during which intense EMIC waves were observed (Engebretson et al, ). These results indicate a missing loss mechanism for ultrarelativistic electrons, which is consistent with previous studies (e.g., Drozdov et al, ).…”

“…Thus, the effects of EMIC waves in this dropout event are still under debate. Using satellite and ground observations, Engebretson et al () investigated EMIC waves and their effect on radiation belt electrons for these GEM challenge events. They also investigated PSD and pitch angle distributions of electrons for Event 2 in this study.…”