Van Allen probes observations of a three-dimensional field line resonance at a plasmaspheric plume
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Field Line Resonances (FLRs) are a critical component in Earth's magnetospheric dynamics, associated with the transfer of energy between Ultra Low Frequency waves and local plasma populations. In this study we investigate how the polarisation of FLRs are impacted by cold plasma density distributions during geomagnetic storms. We present an analysis of Van Allen Probe A observations, where the spacecraft traversed a storm time plasmaspheric plume. We show that the polarisation of the FLR is significantly altered at the sharp azimuthal density gradient of the plume boundary, where the polarisation is intermediate with significant poloidal and toroidal components. These signatures are consistent with magnetohydrodynamic modeling results, providing the first observational evidence of a 3D FLR associated with a plume in Earth's magnetosphere. These results demonstrate the importance of cold plasma in controlling wave dynamics in the magnetosphere, and have important implications for wave-particle interactions at a range of energies.
Sandhu , J , Degeling , A W , Elsden , T , Murphy , K R , Rae , I J , Wright , A N , Hartley , D P & Smith , A 2023 , ' Van Allen probes observations of a three-dimensional field line resonance at a plasmaspheric plume ' , Geophysical Research Letters , vol. 50 , no. 23 , e2023GL106715 . https://doi.org/10.1029/2023GL106715
Geophysical Research Letters
Copyright © 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
DescriptionFunding: JKS, KRM, and IJR acknowledge support from NERC Grants NE/P017185/2, NE/V002554/2, and STFC Grants ST/V006320/1, ST/X001008/1. DPH acknowledges NASA Grant 80NSSC20K1324. ANW was funded in part by STFC Grant ST/W001195/1. AWS was supported by NERC Independent Research Fellowship NE/W009129/1.
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