A diagnosis of the plasma waves responsible for the explosive energy release of substorm onset

Kalmoni, N. M. E., Rae, Jonathan, Watt, Clare, Murphy, K. R., Samara, M., Michell, R. G., Grubbs, G. and Forsyth, C. (2018) A diagnosis of the plasma waves responsible for the explosive energy release of substorm onset. Nature Communications, 9 (1). ISSN 2041-1723

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Official URL: https://doi.org/10.1038/s41467-018-07086-0

Abstract

During geomagnetic substorms, stored magnetic and plasma thermal energies are explosively converted into plasma kinetic energy. This rapid reconfiguration of Earth’s nightside magnetosphere is manifest in the ionosphere as an auroral display that fills the sky. Progress in understanding of how substorms are initiated is hindered by a lack of quantitative analysis of the single consistent feature of onset; the rapid brightening and structuring of the most equatorward arc in the ionosphere. Here, we exploit state-of-the-art auroral measurements to construct an observational dispersion relation of waves during substorm onset. Further, we use kinetic theory of high-beta plasma to demonstrate that the shear Alfven wave dispersion relation bears remarkable similarity to the auroral dispersion relation. In contrast to prevailing theories of substorm initiation, we demonstrate that auroral beads seen during the majority of substorm onsets are likely the signature of kinetic Alfven waves driven unstable in the high-beta magnetotail.

Item Type: Article
Uncontrolled Keywords: Plasma physics, Magnetospheric physics, Aurora
Subjects: F300 Physics
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 04 Aug 2020 09:29
Last Modified: 04 Aug 2020 09:30
URI: http://nrl.northumbria.ac.uk/id/eprint/43964

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