Phase Space Density Analysis of Outer Radiation Belt Electron Energization and Loss During Geoeffective and Nongeoeffective Sheath Regions

Milla M. H. Kalliokoski; Emilia K. J. Kilpua; Adnane Osmane; Allison N. Jaynes; Drew L. Turner; Harriet George; Lucile Turc; Minna Palmroth

doi:10.1029/2021JA029662

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Phase Space Density Analysis of Outer Radiation Belt Electron Energization and Loss During Geoeffective and Nongeoeffective Sheath Regions

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Phase Space Density Analysis of Outer Radiation Belt Electron Energization and Loss During Geoeffective and Nongeoeffective Sheath Regions

Milla M. H. Kalliokoski, Emilia K. J. Kilpua, Adnane Osmane, Allison N. Jaynes, Drew L. Turner, Harriet George, Lucile Turc and Minna Palmroth

Journal of geophysical research. Space physics, Vol.127(3), e2021JA029662

03/01/2022

DOI: 10.1029/2021JA029662

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Abstract

Coronal mass ejection driven sheath regions are one of the key drivers of drastic outer radiation belt responses. The response can however be significantly different based on the sheath properties and the associated inner magnetospheric wave activity. We performed two case studies on the effects of sheaths on outer belt electrons of various energies using data from the Van Allen Probes. One sheath caused a major geomagnetic disturbance and the other had only a minor impact. We especially investigated the phase space density (PSD) of seed, core, and ultrarelativistic electrons to determine the dominant energization and loss processes taking place during the events. Both sheaths produced substantial variation in the electron fluxes from tens of kiloelectronvolts up to ultrarelativistic energies. The responses were however the opposite: the geoeffective sheath mainly led to enhancement, while the nongeoeffective one caused a depletion throughout most of the outer belt. The case studies highlight that both inward and outward radial transport driven by ultra-low frequency waves played an important role in both electron energization and loss. Additionally, PSD radial profiles revealed a local peak that indicated significant acceleration to core energies by chorus waves during the geoeffective event. The distinct responses and different mechanisms in action during these events were related to the timing of the peaked solar wind dynamic pressure causing magnetopause compression, and the differing levels of substorm activity. The most remarkable changes in the radiation belt system occurred in key sheath sub-regions near the shock and the ejecta leading edge.

Physical Sciences

Astronomy & Astrophysics

Science & Technology

Details

Title: Subtitle: Phase Space Density Analysis of Outer Radiation Belt Electron Energization and Loss During Geoeffective and Nongeoeffective Sheath Regions
Creators: Milla M. H. Kalliokoski - University of Helsinki
Emilia K. J. Kilpua - University of Helsinki
Adnane Osmane - Helsinki Institute of Physics
Allison N. Jaynes - University of Iowa
Drew L. Turner - Johns Hopkins University Applied Physics Laboratory
Harriet George - Helsinki Institute of Physics
Lucile Turc - Helsinki Institute of Physics
Minna Palmroth - Helsinki Institute of Physics
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.127(3), e2021JA029662
DOI: 10.1029/2021JA029662
ISSN: 2169-9380
eISSN: 2169-9402
Publisher: Amer Geophysical Union
Number of pages: 21
Grant note: 1312390 / Finnish Centre of Excellence in Research of Sustainable Space (Academy of Finland) SolMAG 724391 / European Research Council (ERC) under the European Union; European Research Council (ERC) 1310445; 322544; 312351 / Academy of Finland 682068-PRESTISSIMO / ERC under the European Union's Horizon 2020 Research and Innovation Programme Project
Language: English
Date published: 03/01/2022
Academic Unit: Physics and Astronomy; University College Courses
Record Identifier: 9984429012902771

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