Carriers and sources of magnetopause current: MMS Case Study

Carriers and sources of magnetopause current: MMS Case Study

We investigate the current carriers and current sources of an ion scale tangential magnetopause current layer using the Magnetospheric Multiscale four spacecraft data. Within this magnetopause current layer, ions and electrons equally contribute to the perpendicular current, while electrons carry nearly all the parallel current. The energy range of all these current carriers is predominantly from middle to high (>100 eV), where particles with higher energies are more efficient in producing the current. By comparing each term, two-fluid magnetohydrodynamic (MHD) theory is able to describe the current sources to a large degree because the sum of all the perpendicular currents from MHD theory could account for the currents observed. In addition, we find that the ion diamagnetic current is the main source of the total perpendicular current, while the curvature current can be neglected. Nevertheless, ions and electrons both carry comparable current due to the redistribution of the electric field and show features beyond the classic Chapman-Ferraro model, particularly on the front side of the boundary layer where the electric field reversal is most intense. We also show a second, comparative event in which ions do not satisfy MHD theory, while the electrons do. The small-scale, adiabatic parameter (square of curvature radius/gyroradius) supports our interpretation that this second event contains ion scale substructure. We suggest that comparing the predicted MHD current with plasma current can be a good method to judge whether the MHD theory is satisfied in each specific circumstance, especially for high-precision Magnetospheric Multiscale data.

Current carriers, Current sources, Magnetopause current, Two-fluid MHD

5464-5475

Dong, X. C.

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Dunlop, M. W.

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Wang, T. Y.

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Cao, J. B.

4fcb5435-f978-467a-93c4-11ce0d25035f

Trattner, K. J.

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Bamford, R.

f7b0d205-7772-4720-b5ba-7980b7a000b7

Russell, C. T.

0beb88bf-9d0e-4b75-80ae-61ba3776ce59

Bingham, R.

9f16ac1d-06df-4aac-bf65-aa06c2c2f55a

Strangeway, R. J.

2fd4cc7c-d923-448d-babf-ce95399ed494

Fear, R. C.

8755b9ed-c7dc-4cbb-ac9b-56235a0431ab

Giles, B. L.

eceb7be2-b272-40cb-a9af-82687b2708fd

Torbert, R. B.

dfb49866-d44d-4404-81cd-22cef59d8f03

Dong, X. C.

061141e9-b73b-43d5-aed8-b97142972657

Dunlop, M. W.

88ebb777-3e0c-43b2-9684-0ef314439ec5

Wang, T. Y.

a15c5a01-2590-4ed1-9f15-289c6a29d15f

Cao, J. B.

4fcb5435-f978-467a-93c4-11ce0d25035f

Trattner, K. J.

16c79a6f-f7b9-4be8-bf69-b64445a72f2c

Bamford, R.

f7b0d205-7772-4720-b5ba-7980b7a000b7

Russell, C. T.

0beb88bf-9d0e-4b75-80ae-61ba3776ce59

Bingham, R.

9f16ac1d-06df-4aac-bf65-aa06c2c2f55a

Strangeway, R. J.

2fd4cc7c-d923-448d-babf-ce95399ed494

Fear, R. C.

8755b9ed-c7dc-4cbb-ac9b-56235a0431ab

Giles, B. L.

eceb7be2-b272-40cb-a9af-82687b2708fd

Torbert, R. B.

dfb49866-d44d-4404-81cd-22cef59d8f03

Dong, X. C., Dunlop, M. W., Wang, T. Y., Cao, J. B., Trattner, K. J., Bamford, R., Russell, C. T., Bingham, R., Strangeway, R. J., Fear, R. C., Giles, B. L. and Torbert, R. B.
(2018)
Carriers and sources of magnetopause current: MMS Case Study.
*Journal of Geophysical Research: Space Physics*, 123 (7), .
(doi:10.1029/2018JA025292).

## Abstract

We investigate the current carriers and current sources of an ion scale tangential magnetopause current layer using the Magnetospheric Multiscale four spacecraft data. Within this magnetopause current layer, ions and electrons equally contribute to the perpendicular current, while electrons carry nearly all the parallel current. The energy range of all these current carriers is predominantly from middle to high (>100 eV), where particles with higher energies are more efficient in producing the current. By comparing each term, two-fluid magnetohydrodynamic (MHD) theory is able to describe the current sources to a large degree because the sum of all the perpendicular currents from MHD theory could account for the currents observed. In addition, we find that the ion diamagnetic current is the main source of the total perpendicular current, while the curvature current can be neglected. Nevertheless, ions and electrons both carry comparable current due to the redistribution of the electric field and show features beyond the classic Chapman-Ferraro model, particularly on the front side of the boundary layer where the electric field reversal is most intense. We also show a second, comparative event in which ions do not satisfy MHD theory, while the electrons do. The small-scale, adiabatic parameter (square of curvature radius/gyroradius) supports our interpretation that this second event contains ion scale substructure. We suggest that comparing the predicted MHD current with plasma current can be a good method to judge whether the MHD theory is satisfied in each specific circumstance, especially for high-precision Magnetospheric Multiscale data.

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## More information

Accepted/In Press date: 22 June 2018

e-pub ahead of print date: 17 July 2018

Keywords:
Current carriers, Current sources, Magnetopause current, Two-fluid MHD

## Identifiers

Local EPrints ID: 425599

URI: http://eprints.soton.ac.uk/id/eprint/425599

ISSN: 2169-9380

PURE UUID: 3c3dd243-c00a-4472-ab60-12b046a49bef

## Catalogue record

Date deposited: 25 Oct 2018 16:30

Last modified: 08 Nov 2022 02:43

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## Contributors

Author:
X. C. Dong

Author:
M. W. Dunlop

Author:
T. Y. Wang

Author:
J. B. Cao

Author:
K. J. Trattner

Author:
R. Bamford

Author:
C. T. Russell

Author:
R. Bingham

Author:
R. J. Strangeway

Author:
B. L. Giles

Author:
R. B. Torbert

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