Wave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts

• DOI: 10.1038/ncomms12883
• Publication Date: 2016-09-28T10:39:43Z
• Authors: Yuri Y. Shprits; Alexander Y. Drozdov; Maria Spasojevic; Adam C. Kellerman; Maria E. Usanova; Mark J. Engebretson; Oleksiy V. Agapitov; Irina S. Zhelavskaya; Tero J. Raita; Harlan E. Spence; Daniel N. Baker; Hui Zhu; Nikita A. Aseev
• Keywords: Science; Physical Sciences; Q; Institut für Physik und Astronomie; Nuclear and Plasma Physics; 530; 01 natural sciences; Article; 0105 earth and related environmental sciences

AbstractThe dipole configuration of the Earth’s magnetic field allows for the trapping of highly energetic particles, which form the radiation belts. Although significant advances have been made in understanding the acceleration mechanisms in the radiation belts, the loss processes remain poorly understood. Unique observations on 17 January 2013 provide detailed information throughout the belts on the energy spectrum and pitch angle (angle between the velocity of a particle and the magnetic field) distribution of electrons up to ultra-relativistic energies. Here we show that although relativistic electrons are enhanced, ultra-relativistic electrons become depleted and distributions of particles show very clear telltale signatures of electromagnetic ion cyclotron wave-induced loss. Comparisons between observations and modelling of the evolution of the electron flux and pitch angle show that electromagnetic ion cyclotron waves provide the dominant loss mechanism at ultra-relativistic energies and produce a profound dropout of the ultra-relativistic radiation belt fluxes.