Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

Abstract

Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy distribution, and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is the first balloon REP event with closely conjugate EMIC wave observations, and our study employs the most detailed quantitative analysis on the link of EMIC waves with observed REP to date.

A Statistical Study of the Spatial Extent of Relativistic Electron Precipitation With Polar Orbiting Environmental Satellites

“…Precipitation of >1 MeV electrons lasting from minutes to hours has been observed by balloons that were located around L ∼ 4-7 and late afternoon/dusk sector (Millan et al, 2002) with strong evidence of being initiated by scattering from electromagnetic ion cyclotron (EMIC) waves (Clilverd et al, 2006;Li et al, 2014;Lorentzen et al, 2000).…”

Investigating energetic electron precipitation through combining ground‐based and balloon observations

“…Several authors have analyzed BARREL X‐ray spectra in order to provide insight into the precipitating electron energy spectra occurring during specific events. Li et al [] studied an EMIC event at 03:00 UT on 17 January 2013 and calculated diffusion coefficients from a helium‐band EMIC wave by using observed wave power and background conditions from GOES 13 and the Van Allen Probes. The simulated BARREL X‐ray spectra best fit the observations when they were scaled down by a factor of 2.9.…”

Confirmation of EMIC wave‐driven relativistic electron precipitation

“…A number of case studies have been published using direct observations of electron precipitation, though without corresponding wave measurements [e.g., Bortnik et al , ; Millan et al , , ]. More recently, an increase in the number of ground‐based stations capable of detecting EMIC waves as well as the launch of the Van Allen Probes has seen a number of case studies published combining both wave and electron precipitation measurements [e.g., Miyoshi et al , ; Rodger et al , ; Li et al , ; Clilverd et al , ; Usanova et al , ]. Due to the experimental limitations of these studies, however, it is difficult to draw wholesale conclusions on EMIC wave precipitation characteristics.…”