Van Allen Probes Observations of a Three-Dimensional Field Line Resonance at a Plasmaspheric Plume

Jasmine Kaur Sandhu*, Alexander W. Degeling, Andrew N. Wright, Andy Smith, David Paul Hartley, Jonathan Rae, Kyle Robert Murphy, Tom Elsden

*Corresponding author for this work

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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.

Original languageEnglish
Article numbere2023GL106715
Number of pages10
JournalGeophysical Research Letters
Issue number23
Early online date30 Nov 2023
Publication statusPublished - 16 Dec 2023

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