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Ultralow Frequency Waves as an Intermediary for Solar Wind Energy Input Into the Radiation Belts

Georgiou, M; Daglis, IA; Rae, IJ; Zesta, E; Sibeck, DG; Mann, IR; Balasis, G; (2018) Ultralow Frequency Waves as an Intermediary for Solar Wind Energy Input Into the Radiation Belts. Journal of Geophysical Research: Space Physics , 123 (12) pp. 10090-10108. 10.1029/2018JA025355. Green open access

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Abstract

Enhancements of electron fluxes in the outer radiation belt have been closely linked to increases in solar wind speed and density as well as to prolonged intervals of southward interplanetary magnetic field. Periodic oscillations in the Earth's magnetic field with frequencies in the range of a few millihertz (ultralow frequency or ultralow frequency waves) may be an intermediary through which these solar wind drivers influence radiation belt dynamics due to their potential for resonant interactions with energetic electrons causing the radial migration of resonant electrons. Using data from more than 180 ground magnetometers contributing to the worldwide SuperMAG collaboration, we explore possible relationships between relativistic electron flux variations and the spatial and temporal profiles of ultralow frequency wave power contained in the Pc5 frequency band (2–7 mHz). During 19 geomagnetic storms marked by relativistic (1.5 MeV < E < 6 MeV) electron flux enhancements and 19 storms that led to prolonged electron flux depletions, Pc5 wave power is found penetrating to L shells as low as 2–3. The enhancement of Pc5 wave power starts almost simultaneously with the storm onset. The depth of wave activity penetration was found associated with the strength of geomagnetic activity (Spearman's ρ = 0.54), which is also related to the location of electron flux maximum observed in the recovery phase. Pc5 wave activity persists longer (for up to ≈62 hr) for those storms that produced relativistic electrons. We also investigate the combination of interplanetary conditions necessary to differentiate the response of relativistic electron fluxes to geomagnetic storms. A coupling function that captures the increased reconnection rate at the dayside magnetopause affecting magnetospheric processes which may produce Pc5 wave power offers an additional key to further understanding the outer belt dynamics.

Type: Article
Title: Ultralow Frequency Waves as an Intermediary for Solar Wind Energy Input Into the Radiation Belts
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2018JA025355
Publisher version: https://doi.org/10.1029/2018JA025355
Language: English
Additional information: This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. https://creativecommons.org/licenses/by/4.0/
Keywords: magnetic storms, radiation belts, relativistic electrons, ULF waves, solar wind, interplanetary coronal mass ejections
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10068115
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