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A new auroral phenomenon, the anti-black aurora

A new auroral phenomenon, the anti-black aurora
A new auroral phenomenon, the anti-black aurora

Black auroras are small-scale features embedded in the diffuse background aurora, typically occurring post-substorm after magnetic midnight and with an eastward drift imposed. Black auroras show a significant reduction in optical brightness compared to the surrounding diffuse aurora, and can appear as slow-moving arcs or rapidly-moving patches and arc segments. We report, for the first time, an even more elusive small-scale optical structure that has always been observed occurring paired with ∼ 10% of black aurora patches. A patch or arc segment of enhanced luminosity, distinctly brighter than the diffuse background, which we name the anti-black aurora, may appear adjacent to the black aurora. The anti-black aurora is of similar shape and size, and always moves in parallel to the drifting black aurora, although it may suddenly switch sides for no apparent reason. The paired phenomenon always drifts with the same average speed in an easterly direction. From the first dual-wavelength (427.8 nm and 844.6 nm) optical observations of the phenomenon recorded on 12 March 2016 outside Tromsø Norway, we show that the anti-black and black auroras have a higher and lower mean energy, respectively, of the precipitating electrons compared to the diffuse background.

2045-2322
Nel, A.E.
e9cefed3-2933-44f5-96c6-51d6bbc549b9
Kosch, M. J.
0497f1fb-094b-4f6b-98dd-4ced2faffb3b
Whiter, D.
9a30d7b6-ea41-44fb-bd52-3ff1964eca5c
Gustavsson, B.
d88050c7-3139-4b1f-a0c1-a70d7288a3b6
Aslaksen, T.
cd9975d7-e917-4bde-b47d-0d9a44ae899f
Nel, A.E.
e9cefed3-2933-44f5-96c6-51d6bbc549b9
Kosch, M. J.
0497f1fb-094b-4f6b-98dd-4ced2faffb3b
Whiter, D.
9a30d7b6-ea41-44fb-bd52-3ff1964eca5c
Gustavsson, B.
d88050c7-3139-4b1f-a0c1-a70d7288a3b6
Aslaksen, T.
cd9975d7-e917-4bde-b47d-0d9a44ae899f

Nel, A.E., Kosch, M. J., Whiter, D., Gustavsson, B. and Aslaksen, T. (2021) A new auroral phenomenon, the anti-black aurora. Scientific Reports, 11 (1), [1829]. (doi:10.1038/s41598-021-81363-9).

Record type: Article

Abstract

Black auroras are small-scale features embedded in the diffuse background aurora, typically occurring post-substorm after magnetic midnight and with an eastward drift imposed. Black auroras show a significant reduction in optical brightness compared to the surrounding diffuse aurora, and can appear as slow-moving arcs or rapidly-moving patches and arc segments. We report, for the first time, an even more elusive small-scale optical structure that has always been observed occurring paired with ∼ 10% of black aurora patches. A patch or arc segment of enhanced luminosity, distinctly brighter than the diffuse background, which we name the anti-black aurora, may appear adjacent to the black aurora. The anti-black aurora is of similar shape and size, and always moves in parallel to the drifting black aurora, although it may suddenly switch sides for no apparent reason. The paired phenomenon always drifts with the same average speed in an easterly direction. From the first dual-wavelength (427.8 nm and 844.6 nm) optical observations of the phenomenon recorded on 12 March 2016 outside Tromsø Norway, we show that the anti-black and black auroras have a higher and lower mean energy, respectively, of the precipitating electrons compared to the diffuse background.

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More information

Accepted/In Press date: 18 December 2020
Published date: 19 January 2021

Identifiers

Local EPrints ID: 446479
URI: http://eprints.soton.ac.uk/id/eprint/446479
ISSN: 2045-2322
PURE UUID: e93ad696-3590-453e-8015-2413fd84d8f1
ORCID for D. Whiter: ORCID iD orcid.org/0000-0001-7130-232X

Catalogue record

Date deposited: 11 Feb 2021 17:30
Last modified: 18 Feb 2021 17:11

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Contributors

Author: A.E. Nel
Author: M. J. Kosch
Author: D. Whiter ORCID iD
Author: B. Gustavsson
Author: T. Aslaksen

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