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Interhemispheric survey of polar cap aurora

Interhemispheric survey of polar cap aurora
Interhemispheric survey of polar cap aurora

This study investigates the interhemispheric nature of polar cap auroras via ultraviolet imaging, combined with particle data, to determine whether they occur on open or closed field lines. Data from the SSUSI (Special Sensor Ultraviolet Spectrographic Imager) instrument on board the DMSP (Defence Meteorological Satellite Program) spacecraft are examined. The DMSP spacecraft are in 90-min orbits; hence, images of each hemisphere are separated by 45 min providing a good opportunity for interhemispheric study. 21 polar cap arc (PCA) events are recorded in December 2015 which have particle data from the SSJ/4 particle spectrometer associated with an arc in at least one hemisphere. Nine events are found to contain "arcs" consistent with a closed field line mechanism, that is, arcs associated with an ion signature present in both hemispheres. Six events contained arcs that were consistent with an "open field line" mechanism, that is, they were associated with electron-only precipitation. Events containing arcs that were not consistent with either of these expectations are also explored, including an example of a "non-conjugate" theta aurora and an interesting example of auroral morphology similar to a PCA which is associated with a geomagnetic storm. Seasonal effects are also investigated through a statistical analysis of PCAs over 4 months in 2015. It is found that PCAs are visible in the SSUSI data at least 20% of the time and that it is likely some are missed due to the spacecraft field of view and poor sensitivity in the summer hemisphere due to increased solar illumination.

interhemispheric survey, polar cap aurora, polar cap precipitation, polar rain
2169-9380
Reidy, J. A.
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Fear, R. C.
8755b9ed-c7dc-4cbb-ac9b-56235a0431ab
Whiter, D. K.
9a30d7b6-ea41-44fb-bd52-3ff1964eca5c
Lanchester, B.
e864533e-eea0-471f-a3f9-7c70c25be55b
Kavanagh, A. J.
9bad686e-dd05-4e7d-8199-76a55d88956c
Milan, S. E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Carter, J. A.
69d76cf8-ce4f-440f-9472-ea14a7692b06
Paxton, L. J.
5aa386de-58fd-4509-a13f-7ba9cb041b83
Zhang, Y.
781720b5-ad61-4120-bc5f-67f14fd61b09
Reidy, J. A.
7dbc1f34-be44-4269-a3f4-9f490aaaadc7
Fear, R. C.
8755b9ed-c7dc-4cbb-ac9b-56235a0431ab
Whiter, D. K.
9a30d7b6-ea41-44fb-bd52-3ff1964eca5c
Lanchester, B.
e864533e-eea0-471f-a3f9-7c70c25be55b
Kavanagh, A. J.
9bad686e-dd05-4e7d-8199-76a55d88956c
Milan, S. E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Carter, J. A.
69d76cf8-ce4f-440f-9472-ea14a7692b06
Paxton, L. J.
5aa386de-58fd-4509-a13f-7ba9cb041b83
Zhang, Y.
781720b5-ad61-4120-bc5f-67f14fd61b09

Reidy, J. A., Fear, R. C., Whiter, D. K., Lanchester, B., Kavanagh, A. J., Milan, S. E., Carter, J. A., Paxton, L. J. and Zhang, Y. (2018) Interhemispheric survey of polar cap aurora. Journal of Geophysical Research: Oceans. (doi:10.1029/2017JA025153).

Record type: Article

Abstract

This study investigates the interhemispheric nature of polar cap auroras via ultraviolet imaging, combined with particle data, to determine whether they occur on open or closed field lines. Data from the SSUSI (Special Sensor Ultraviolet Spectrographic Imager) instrument on board the DMSP (Defence Meteorological Satellite Program) spacecraft are examined. The DMSP spacecraft are in 90-min orbits; hence, images of each hemisphere are separated by 45 min providing a good opportunity for interhemispheric study. 21 polar cap arc (PCA) events are recorded in December 2015 which have particle data from the SSJ/4 particle spectrometer associated with an arc in at least one hemisphere. Nine events are found to contain "arcs" consistent with a closed field line mechanism, that is, arcs associated with an ion signature present in both hemispheres. Six events contained arcs that were consistent with an "open field line" mechanism, that is, they were associated with electron-only precipitation. Events containing arcs that were not consistent with either of these expectations are also explored, including an example of a "non-conjugate" theta aurora and an interesting example of auroral morphology similar to a PCA which is associated with a geomagnetic storm. Seasonal effects are also investigated through a statistical analysis of PCAs over 4 months in 2015. It is found that PCAs are visible in the SSUSI data at least 20% of the time and that it is likely some are missed due to the spacecraft field of view and poor sensitivity in the summer hemisphere due to increased solar illumination.

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Reidy_et_al-2018-Journal_of_Geophysical_Research%3A_Space_Physics - Version of Record
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Accepted/In Press date: 13 July 2018
e-pub ahead of print date: 20 July 2018
Keywords: interhemispheric survey, polar cap aurora, polar cap precipitation, polar rain

Identifiers

Local EPrints ID: 423162
URI: https://eprints.soton.ac.uk/id/eprint/423162
ISSN: 2169-9380
PURE UUID: 01791218-0ae1-436b-a129-cd8ca42d13c2
ORCID for R. C. Fear: ORCID iD orcid.org/0000-0003-0589-7147
ORCID for D. K. Whiter: ORCID iD orcid.org/0000-0001-7130-232X

Catalogue record

Date deposited: 19 Sep 2018 16:30
Last modified: 20 Jul 2019 00:50

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Contributors

Author: J. A. Reidy
Author: R. C. Fear ORCID iD
Author: D. K. Whiter ORCID iD
Author: B. Lanchester
Author: A. J. Kavanagh
Author: S. E. Milan
Author: J. A. Carter
Author: L. J. Paxton
Author: Y. Zhang

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