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Energization of the ring current by substorms

Energization of the ring current by substorms
Energization of the ring current by substorms

The substorm process releases large amounts of energy into the magnetospheric system, although where the energy is transferred to and how it is partitioned remains an open question. In this study, we address whether the substorm process contributes a significant amount of energy to the ring current. The ring current is a highly variable region, and understanding the energization processes provides valuable insight into how substorm-ring current coupling may contribute to the generation of storm conditions and provide a source of energy for wave driving. In order to quantify the energy input into the ring current during the substorm process, we analyze Radiation Belt Storm Probes Ion Composition Experiment and Helium Oxygen Proton Electron ion flux measurements for H+, O+, and He+. The energy content of the ring current is estimated and binned spatially for L and magnetic local time. The results are combined with an independently derived substorm event list to perform a statistical analysis of variations in the ring current energy content with substorm phase. We show that the ring current energy is significantly higher in the expansion phase compared to the growth phase, with the energy enhancement persisting into the substorm recovery phase. The characteristics of the energy enhancement suggest the injection of energized ions from the tail plasma sheet following substorm onset. The local time variations indicate a loss of energetic H+ ions in the afternoon sector, likely due to wave-particle interactions. Overall, we find that the average energy input into the ring current is ∼9% of the previously reported energy released during substorms.

HOPE, magnetosphere, RBSPICE, ring current, substorms, Van Allen Probes
2169-9380
1-18
Sandhu, J.K.
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Rae, I.J.
25677763-0501-4b69-859e-fab930260c69
Freeman, M.P.
dc974e00-a73d-4d41-a2a8-3c5aebd7a5b5
Forsyth, C.
f3d464cf-81c5-4647-b85a-bc3634bdf076
Gkioulidou, M.
0e6810e5-aa38-47e4-8e9e-07247637445c
Reeves, G.D.
cba38741-5d6c-4eb2-a459-3131819889fc
Spence, H.E.
4d89c525-83ec-4bde-bb80-f1bfeab147fc
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Lam, M.M.
99e04519-04c8-4f47-8658-1c8bb31e1421
Sandhu, J.K.
f7695906-560e-4688-ab02-c387ebc5afc7
Rae, I.J.
25677763-0501-4b69-859e-fab930260c69
Freeman, M.P.
dc974e00-a73d-4d41-a2a8-3c5aebd7a5b5
Forsyth, C.
f3d464cf-81c5-4647-b85a-bc3634bdf076
Gkioulidou, M.
0e6810e5-aa38-47e4-8e9e-07247637445c
Reeves, G.D.
cba38741-5d6c-4eb2-a459-3131819889fc
Spence, H.E.
4d89c525-83ec-4bde-bb80-f1bfeab147fc
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Lam, M.M.
99e04519-04c8-4f47-8658-1c8bb31e1421

Sandhu, J.K., Rae, I.J., Freeman, M.P., Forsyth, C., Gkioulidou, M., Reeves, G.D., Spence, H.E., Jackman, C.M. and Lam, M.M. (2018) Energization of the ring current by substorms. Journal of Geophysical Research: Space Physics, 1-18. (doi:10.1029/2018JA025766).

Record type: Article

Abstract

The substorm process releases large amounts of energy into the magnetospheric system, although where the energy is transferred to and how it is partitioned remains an open question. In this study, we address whether the substorm process contributes a significant amount of energy to the ring current. The ring current is a highly variable region, and understanding the energization processes provides valuable insight into how substorm-ring current coupling may contribute to the generation of storm conditions and provide a source of energy for wave driving. In order to quantify the energy input into the ring current during the substorm process, we analyze Radiation Belt Storm Probes Ion Composition Experiment and Helium Oxygen Proton Electron ion flux measurements for H+, O+, and He+. The energy content of the ring current is estimated and binned spatially for L and magnetic local time. The results are combined with an independently derived substorm event list to perform a statistical analysis of variations in the ring current energy content with substorm phase. We show that the ring current energy is significantly higher in the expansion phase compared to the growth phase, with the energy enhancement persisting into the substorm recovery phase. The characteristics of the energy enhancement suggest the injection of energized ions from the tail plasma sheet following substorm onset. The local time variations indicate a loss of energetic H+ ions in the afternoon sector, likely due to wave-particle interactions. Overall, we find that the average energy input into the ring current is ∼9% of the previously reported energy released during substorms.

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Sandhu et al 2018 Journal of Geophysical Research Space Physics - Version of Record
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Accepted/In Press date: 12 September 2018
e-pub ahead of print date: 17 September 2018
Keywords: HOPE, magnetosphere, RBSPICE, ring current, substorms, Van Allen Probes

Identifiers

Local EPrints ID: 425532
URI: https://eprints.soton.ac.uk/id/eprint/425532
ISSN: 2169-9380
PURE UUID: 723f4f4b-d228-437d-a2c2-e845f583ce2d

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Date deposited: 24 Oct 2018 16:30
Last modified: 02 Dec 2019 17:53

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Contributors

Author: J.K. Sandhu
Author: I.J. Rae
Author: M.P. Freeman
Author: C. Forsyth
Author: M. Gkioulidou
Author: G.D. Reeves
Author: H.E. Spence
Author: C.M. Jackman
Author: M.M. Lam

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