University of Oulu

George, H., Kilpua, E., Osmane, A., Asikainen, T., Kalliokoski, M. M. H., Rodger, C. J., Dubyagin, S., and Palmroth, M.: Outer Van Allen belt trapped and precipitating electron flux responses to two interplanetary magnetic clouds of opposite polarity, Ann. Geophys., 38, 931–951,, 2020.

Outer Van Allen belt trapped and precipitating electron flux responses to two interplanetary magnetic clouds of opposite polarity

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Author: George, Harriet1; Kilpua, Emilia1; Osmane, Adnane1;
Organizations: 1Department of Physics, University of Helsinki, Helsinki, Finland
2Department of Physics, University of Oulu, Oulu, Finland
3Department of Physics, University of Otago, Dunedin, New Zealand
4Finnish Meteorological Institute, Helsinki, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.3 MB)
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Language: English
Published: Copernicus Publications, 2020
Publish Date: 2021-02-18


Recently, it has been established that interplanetary coronal mass ejections (ICMEs) can dramatically affect both trapped electron fluxes in the outer radiation belt and precipitating electron fluxes lost from the belt into the atmosphere. Precipitating electron fluxes and energies can vary over a range of timescales during these events. These variations depend on the initial energy and location of the electron population and the ICME characteristics and structures. One important factor controlling electron dynamics is the magnetic field orientation within the ejecta that is an integral part of the ICME. In this study, we examine Van Allen Probes (RBSPs) and Polar Orbiting Environmental Satellites (POESs) data to explore trapped and precipitating electron fluxes during two ICMEs. The ejecta in the selected ICMEs have magnetic cloud characteristics that exhibit the opposite sense of the rotation of the north–south magnetic field component (BZ). RBSP data are used to study trapped electron fluxes in situ, while POES data are used for electron fluxes precipitating into the upper atmosphere. The trapped and precipitating electron fluxes are qualitatively analysed to understand their variation in relation to each other and to the magnetic cloud rotation during these events. Inner magnetospheric wave activity was also estimated using RBSP and Geostationary Operational Environmental Satellite (GOES) data. In each event, the largest changes in the location and magnitude of both the trapped and precipitating electron fluxes occurred during the southward portion of the magnetic cloud. Significant changes also occurred during the end of the sheath and at the sheath–ejecta boundary for the cloud with south to north magnetic field rotation, while the ICME with north to south rotation had significant changes at the end boundary of the cloud. The sense of rotation of BZ and its profile also clearly affects the coherence of the trapped and/or precipitating flux changes, timing of variations with respect to the ICME structures, and flux magnitude of different electron populations. The differing electron responses could therefore imply partly different dominant acceleration mechanisms acting on the outer radiation belt electron populations as a result of opposite magnetic cloud rotation.

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Series: Annales geophysicae
ISSN: 0992-7689
ISSN-E: 1432-0576
ISSN-L: 0992-7689
Volume: 38
Issue: 4
Pages: 931 - 951
DOI: 10.5194/angeo-38-931-2020
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This research has been supported by the Finnish Centre of Excellence in Research of Sustainable Space (grant nos. 312390 and 312351). The work of Timo Asikainen is supported by the Academy of Finland (grant no. 321440). The work of Minna Palmroth is supported by the European Research Council Consolidator (grant no. 682068-PRESTISSIMO) and the Academy of Finland (grant no. 309937). The work of Emilia Kilpua has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme SolMAG (grant no. ERC-COG 724391). Emilia Kilpua has also been supported by the Academy of Finland's project SMASH (grant no. 310445). Open access funding provided by Helsinki University Library.
Academy of Finland Grant Number: 321440
Detailed Information: 321440 (Academy of Finland Funding decision)
Copyright information: © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.