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How Do Ultra‐Low Frequency Waves Access the Inner Magnetosphere During Geomagnetic Storms?
Author(s) -
Rae I. Jonathan,
Murphy Kyle R.,
Watt Clare E.J.,
Sandhu Jasmine K.,
Georgiou Marina,
Degeling Alex W.,
Forsyth Colin,
Bentley Sarah N.,
Staples Frances A.,
Shi Quanqi
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082395
Subject(s) - magnetosphere , ring current , physics , van allen probes , van allen radiation belt , geomagnetic storm , solar wind , geophysics , ultra low frequency , coronal mass ejection , earth's magnetic field , wave power , computational physics , atmospheric sciences , plasma , power (physics) , magnetic field , astronomy , quantum mechanics
Abstract Wave‐particle interactions play a key role in radiation belt dynamics. Traditionally, ultra‐low frequency (ULF) wave‐particle interaction is parameterized statistically by a small number of controlling factors for given solar wind driving conditions or geomagnetic activity levels. Here we investigate solar wind driving of ULF wave power and the role of the magnetosphere in screening that power from penetrating deep into the inner magnetosphere. We demonstrate that during enhanced ring current intensity, the Alfvén continuum plummets, allowing lower frequency waves to penetrate deeper into the magnetosphere than during quiet periods. With this penetration, ULF wave power is able to accumulate closer to the Earth than characterized by statistical models. During periods of enhanced solar wind driving such as coronal mass ejection driven storms, where ring current intensities maximize, the observed penetration provides a simple physics‐based reason for why storm time ULF wave power is different compared to nonstorm time waves.