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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: regular paper 15 Apr 2020

Submitted as: regular paper | 15 Apr 2020

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This preprint is currently under review for the journal ANGEO.

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

Harriet George1, Emilia Kilpua1, Adnane Osmane1, Timo Asikainen2, Milla M. H. Kalliokoski1, Craig J. Rodger3, Stepan Dubyagin4, and Minna Palmroth1 Harriet George et al.
  • 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

Abstract. 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 flux and energy can vary over a range of timescales during these events. These variations depend on the initial energy and location of the electron population, as well as 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 (RBSP) and Polar Orbiting Environmental Satellites (POES) data to explore trapped and precipitating electron fluxes during two ICMEs. The ejecta in the selected ICMEs have magnetic cloud characteristics that exhibit opposite sense of 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 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-cloud 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/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.

Harriet George et al.

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Harriet George et al.

Harriet George et al.


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Latest update: 06 Jun 2020
Publications Copernicus
Short summary
This study compares trapped outer radiation belt electron fluxes to high-latitude precipitating electron fluxes during two interplanetary coronal mass ejections (ICMEs). These ICME had opposite magnetic cloud rotation. The electron response had multiple similarities and differences between the two events, indicating that different acceleration mechanisms acted in the two ICMEs. Van Allen probe data were used for trapped electron flux measurements, and POES was used for precipitating flux data.
This study compares trapped outer radiation belt electron fluxes to high-latitude precipitating...