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2018 
An energetic electron flux dropout due to magnetopause shadowing on 1 June 2013 We examine the mechanisms responsible for the dropout of energetic electron flux during 31 May \textendash 1 June 2013, using Van Allen Probe (RBSP) electron flux data and simulations with the Comprehensive Inner MagnetosphereIonosphere (CIMI) model. During storm main phase, Lshells at RBSP locations are greater than ~ 8, which are connected to open drift shells. Consequently, diminished electron fluxes were observed over a wide range of energies. The combination of drift shell splitting, magnetopause shadowing and drift loss all result in butterfly electron pitchangle distributions (PADs) at the nightside. During storm sudden commencement, RBSP observations display electron butterfly PADs over a wide range of energies. However, it is difficult to determine whether there are butterfly PADs during storm main phase since the maximum observable equatorial pitchangle from RBSP is not larger than ~ 40\textdegree during this period. To investigate the causes of the dropout, the CIMI model is used as a global 4D kinetic inner magnetosphere model. The CIMI model reproduces the dropout with very similar timing and flux levels and PADs along the RBSP trajectory for 593 keV. Furthermore, the CIMI simulation shows butterfly PADs for 593 keV during storm main phase. Based on comparison of observations and simulations, we suggest that the dropout during this event mainly results from magnetopause shadowing. Bin Kang, Suk; Fok, MeiChing; Komar, Colin; Glocer, Alex; Li, Wen; Buzulukova, Natalia; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2018 YEAR: 2018 DOI: 10.1002/2017JA024879 CIMI model; drift loss; dropout; magnetopause shadowing; pitchangle distribution (PAD); RBSP; Van Allen Probes 
2017 
CIMI simulations with newly developed multiparameter chorus and plasmaspheric hiss wave models Numerical simulation studies of the Earth\textquoterights radiation belts are important to understand the acceleration and loss of energetic electrons. The Comprehensive Inner MagnetosphereIonosphere (CIMI) model considers the effects of the ring current and plasmasphere on the radiation belts to obtain plausible results. The CIMI model incorporates pitch angle, energy, and cross diffusion of electrons, due to chorus and plasmaspheric hiss waves. These parameters are calculated using statistical wave distribution models of chorus and plasmaspheric hiss amplitudes. However, currently these wave distribution models are based only on a single parameter, geomagnetic index (AE), and could potentially underestimate the wave amplitudes. Here we incorporate recently developed multiparameter chorus and plasmaspheric hiss wave models based on geomagnetic index and solar wind parameters. We then perform CIMI simulations for two geomagnetic storms and compare the flux enhancement of MeV electrons with data from the Van Allen Probes and Akebono satellites. We show that the relativistic electron fluxes calculated with multiparameter wave models resembles the observations more accurately than the relativistic electron fluxes calculated with singleparameter wave models. This indicates that wave models based on a combination of geomagnetic index and solar wind parameters are more effective as inputs to radiation belt models. Aryan, Homayon; Sibeck, David; Bin Kang, Suk; Balikhin, Michael; Fok, MeiChing; Agapitov, Oleksiy; Komar, Colin; Kanekal, Shrikanth; Nagai, Tsugunobu; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2017 YEAR: 2017 DOI: 10.1002/2017JA024159 Chorus and plasmaspheric hiss wave models; CIMI numerical simulations; Geomagnetic storm events; Radiation belt electron flux enhancements; Van Allen Probes; VLF waves; Waveparticle interaction 
2015 
Electromagnetic ion cyclotron (EMIC) waves are closely related to precipitating loss of relativistic electrons in the radiation belts, and thereby, a model of the radiation belts requires inclusion of the pitch angle diffusion caused by EMIC waves. We estimated the pitch angle diffusion rates and the corresponding precipitation time scales caused by H and He band EMIC waves using the Tsyganenko 04 (T04) magnetic field model at their probable regions in terms of geomagnetic conditions. The results correspond to enhanced pitch angle diffusion rates and reduced precipitation time scales compared to those based on the dipole model, up to several orders of magnitude for storm times. While both the plasma density and the magnetic field strength varied in these calculations, the reduction of the magnetic field strength predicted by the T04 model was found to be the main cause of the enhanced diffusion rates relative to those with the dipole model for the same Li values, where Li is defined from the ionospheric foot points of the field lines. We note that the bounceaveraged diffusion rates were roughly proportional to the inversion of the equatorial magnetic field strength and thus suggest that scaling the diffusion rates with the magnetic field strength provides a good approximation to account for the effect of the realistic field model in the EMIC wavepitch angle diffusion modeling. Bin Kang, Suk; Min, KyoungWook; Fok, MeiChing; Hwang, Junga; Choi, CheongRim; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2015 YEAR: 2015 DOI: 10.1002/2014JA020644 EMIC waves; pitch angle diffusion rate; precipitation time scale; quasilinear theory; realistic field model; Relativistic electron 
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