Energetic electron precipitation driven by electromagnetic ion cyclotron waves from ELFIN's low altitude perspective
Abstract
We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data from the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at 0.5 MeV which are abrupt (bursty) with significant substructure (occasionally down to sub-second timescale). Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Using two years of ELFIN data, we assemble a statistical database of 50 events of strong EMIC wave-driven precipitation. Most reside at L=5-7 at dusk, while a smaller subset exists at L=8-12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an L-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio's spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven 1MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to 200-300 keV by much less intense higher frequency EMIC waves. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.
Keywords
Cite
@article{arxiv.2211.15653,
title = {Energetic electron precipitation driven by electromagnetic ion cyclotron waves from ELFIN's low altitude perspective},
author = {V. Angelopoulos and X. -J. Zhang and A. V. Artemyev and D. Mourenas and E. Tsai and C. Wilkins and A. Runov and J. Liu and D. L. Turner and W. Li and K. Khurana and R. E. Wirz and V. A. Sergeev and X. Meng and J. Wu and M. D. Hartinger and T. Raita and Y. Shen and X. An and X. Shi and M. F. Bashir and X. Shen and L. Gan and M. Qin and L. Capannolo and Q. Ma and C. L. Russell and E. V. Masongsong and R. Caron and I. He and L. Iglesias and S. Jha and J. King and S. Kumar and K. Le and J. Mao and A. McDermott and K. Nguyen and A. Norris and A. Palla and Roosnovo and J. Tam and E. Xie and R. C. Yap and S. Ye and C. Young and L. A. Adair and C. Shaffer and M. Chung and P. Cruce and M. Lawson and D. Leneman and M. Allen and M. Anderson and M. Arreola-Zamora and J. Artinger and J. Asher and D. Branchevsky and M. Cliffe and K. Colton and C. Costello and D. Depe and B. W. Domae and S. Eldin and L. Fitzgibbon and A. Flemming and D. M. Frederick and A. Gilbert and B. Hesford and R. Krieger and K. Lian and E. McKinney and J. P. Miller and C. Pedersen and Z. Qu and R. Rozario and M. Rubly and R. Seaton and A. Subramanian and S. R. Sundin and A. Tan and D. Thomlinson and W. Turner and G. Wing and C. Wong and A. Zarifian},
journal= {arXiv preprint arXiv:2211.15653},
year = {2023}
}