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EP: Fachverband Extraterrestrische Physik
EP 12: Near-Earth Space II
EP 12.1: Invited Talk
Thursday, March 23, 2023, 15:45–16:15, ZEU/0160
Ultra-relativistic Electrons in the Earth's Van Allen Radiation Belts — •Yuri Y. Shprits1,2,3, Hayley Allison1, Nikita Aseev1, Dedong Wang1, and Alexander Drozdov3 — 1Department of Geophysics, German Research Center for Geociences, GFZ, Potsdam, Germany — 2Institute of Physics and Astronomy, University of Potsdam, Germany — 3Department of Earth, Planetary, and Space Sciences, UCLA
New measurements from the NASAs Van Allen Probes demonstrate that the Earth radiation belts cannot be considered as a bulk population above approximately electron rest mass, but ultra-relativistic electrons form a new population that shows a very different morphology and behavior. We show that acceleration to multi-MeV occurs locally due to energy diffusion by whistler mode waves. Local heating appears to be able to transport electrons in energy space from 100s of keV all the way to ultra-relativistic energies. Acceleration to such high energies occurs only for the conditions when cold plasma in the trough region shows extreme depletions. The difference between the loss mechanisms at MeV and multi-MeV energies is due to EMIC waves that can very efficiently scatter ultra-relativistic electrons but leave MeV electrons unaffected. We also present how the new understanding can be used to produce the most accurate data-assimilative forecast. Under the recently funded EU Horizon 2020 Project Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER), we will study how ensemble forecasting from the Sun can produce long-term probabilistic forecasts of the radiation environment.