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

Abstract

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 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.

Impact of solar cycle on the non-linearity of the relationship between the solar wind parameters and geomagnetic conditions

“…Southward IMF within the ejecta can lead to losses of radiation belt electrons across the magnetopause, as the more effective reconnection erodes the magnetopause closer to the Earth (George et al, 2020;George et al, 2022). In addition, the rotation profile of the magnetic field within the ejecta, south-north or north-south, can impact whether significant changes in the electron population occur during the leading or trailing boundary of the ejecta (George et al, 2020). SIRs also typically cause losses of relativistic electrons although to a smaller extent than ICME sheath regions (e.g.…”

Contributions to Loss Across the Magnetopause During an Electron Dropout Event

“…The K P parametrization results in 3‐hr time resolution of the radial diffusion coefficients and this time resolution may result in inaccuracies, particularly during geomagnetic storms. The radiation belt response can be significantly affected by the internal structures of ICMEs driving the storm, such as sheath regions (Kalliokoski et al., 2020 ) and the magnetic polarity of the ejecta (George et al., 2020 ), that occur on relatively short timescales. Magnetospheric wave activity is no exception: the ULF wave power can vary by orders of magnitude during different phases of geomagnetic storms (Sandhu et al., 2021 ).…”

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

“…On the other hand, at high latitudes, the 90° telescope measures fluxes in the bounce and drift loss cones, possibly not measuring the trapped fluxes at all (Rodger et al, 2010). To estimate the low-energy electron precipitation, we combined the data from the two telescopes and considered the geometric mean of the fluxes (e.g., George et al, 2020;Hargreaves et al, 2010;Rodger et al, 2013):…”