Japan Geoscience Union Meeting 2023

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[E] Oral

P (Space and Planetary Sciences ) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM13] Dynamics of the Inner Magnetospheric System

Tue. May 23, 2023 10:45 AM - 12:00 PM 101 (International Conference Hall, Makuhari Messe)

convener:Kunihiro Keika(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo ), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Theodore E Sarris(Democritus University of Thrace), Evan G Thomas(Dartmouth College), Chairperson:Shoya Matsuda(Kanazawa University), Satoko Nakamura(Institute for Space-Earth Environmental Research, Nagoya University), Kazuhiro Yamamoto(Graduate School of Science, The University of Tokyo), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Kunihiro Keika(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)

11:10 AM - 11:25 AM

[PEM13-02] Van Allen Probes and GPS observations of the outer radiation belt electron dynamics during sheath regions of coronal mass ejections

*Milla Kalliokoski1,2, Michael Henderson3, Steven Morley3, Emilia Kilpua2, Adnane Osmane2, Leonid Olifer4, Drew Turner5, Allison Jaynes6, Harriet George2,7, Sanni Hoilijoki2, Lucile Turc2, Minna Palmroth2,8 (1.JAXA ISAS, 2.Univ. Helsinki, 3.LANL, 4.Univ. Alberta, 5.JHUAPL, 6.Univ. Iowa, 7.LASP, 8.FMI)

Keywords:Earth, radiation belt, electrons

Turbulent and compressed sheath regions ahead of interplanetary coronal mass ejections are key drivers of dramatic changes in the electron fluxes in the Earth’s outer radiation belt. They are also associated with elevated wave activity in the inner magnetosphere. These changes in electron fluxes can occur on timescales of tens of minutes that are not readily captured by a two-satellite mission such as the Van Allen Probes due to long revisit times. The recently released Global Positioning System (GPS) data set, on the other hand, provides a larger number of measurements at a given location within a given amount of time, owing to the many satellites in the constellation. In our statistical study on the impact of sheath regions on the outer radiation belt, we investigated events in 2012-2018 at timescales of 6 hours (Van Allen Probes data) and 30 minutes (GPS data). The study showed that the flux response to sheaths as reported from Van Allen Probes observations is reproduced by GPS data. We highlight that the shorter timescale allowed by GPS data further confirms that the energy and L-shell dependent flux changes are associated with the sheaths rather than the following ejecta. Additionally, we studied the electron phase space density, which is a key quantity for identifying non-adiabatic electron dynamics. This showed that electrons are effectively accelerated only during geoeffective sheaths (SYM-H < -30 nT). Outer belt losses are common for all sheaths, and the lost electrons are replenished during the early ejecta.