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Energy and flux variations across thin auroral arcs

Energy and flux variations across thin auroral arcs
Energy and flux variations across thin auroral arcs
Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small and medium field-of-view imagers and the EISCAT radar. The energy and flux of the precipitating electrons, volume emission rates and local electric fields in the ionosphere have been determined at high temporal (up to 30 Hz) and spatial (down to tens of metres) resolution. A new time-dependent inversion model is used to derive energy spectra from EISCAT electron density profiles. The energy and flux are also derived independently from optical emissions combined with ion-chemistry modelling, and a good agreement is found. A robust method to obtain detailed 2-D maps of the average energy and number flux of small scale aurora is presented. The arcs are stretched in the north-south direction, and the lowest energies are found on the western, leading edges of the arcs. The large ionospheric electric fields (250 mV m?1) found from tristatic radar measurements are evidence of strong currents associated with the region close to the optical arcs. The different data sets indicate that the arcs appear on the boundaries between regions with different average energy of diffuse precipitation, caused by pitch-angle scattering. The two thin arcs on these boundaries are found to be related to an increase in number flux (and thus increased energy flux) without an increase in energy
0992-7689
1699-1712
Dahlgren, H.
8d021086-b328-46fd-affd-a7c8d2b4687e
Gustavsson, B.
5ef90805-5748-4626-a3b6-85554fac934d
Lanchester, B.S.
e864533e-eea0-471f-a3f9-7c70c25be55b
Ivchenko, N.
c892df9e-e2a0-450f-bf77-2673e029f565
Brändström, U.
5d98b892-2553-4f92-a78e-b8524018cfbb
Whiter, D.K.
9a30d7b6-ea41-44fb-bd52-3ff1964eca5c
Sergienko, T.
f29518bd-fb08-4dcb-ad38-ad48fc8689f0
Sandahl, I.
f0c1ca8b-f5ff-4c5b-9856-8a79fe002f84
Marklund, G.
ca3a83f3-e335-4d69-b5e3-2dad226e339f
Dahlgren, H.
8d021086-b328-46fd-affd-a7c8d2b4687e
Gustavsson, B.
5ef90805-5748-4626-a3b6-85554fac934d
Lanchester, B.S.
e864533e-eea0-471f-a3f9-7c70c25be55b
Ivchenko, N.
c892df9e-e2a0-450f-bf77-2673e029f565
Brändström, U.
5d98b892-2553-4f92-a78e-b8524018cfbb
Whiter, D.K.
9a30d7b6-ea41-44fb-bd52-3ff1964eca5c
Sergienko, T.
f29518bd-fb08-4dcb-ad38-ad48fc8689f0
Sandahl, I.
f0c1ca8b-f5ff-4c5b-9856-8a79fe002f84
Marklund, G.
ca3a83f3-e335-4d69-b5e3-2dad226e339f

Dahlgren, H., Gustavsson, B., Lanchester, B.S., Ivchenko, N., Brändström, U., Whiter, D.K., Sergienko, T., Sandahl, I. and Marklund, G. (2011) Energy and flux variations across thin auroral arcs. Annales Geophysicae, 29, 1699-1712. (doi:10.5194/angeo-29-1699-2011).

Record type: Article

Abstract

Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small and medium field-of-view imagers and the EISCAT radar. The energy and flux of the precipitating electrons, volume emission rates and local electric fields in the ionosphere have been determined at high temporal (up to 30 Hz) and spatial (down to tens of metres) resolution. A new time-dependent inversion model is used to derive energy spectra from EISCAT electron density profiles. The energy and flux are also derived independently from optical emissions combined with ion-chemistry modelling, and a good agreement is found. A robust method to obtain detailed 2-D maps of the average energy and number flux of small scale aurora is presented. The arcs are stretched in the north-south direction, and the lowest energies are found on the western, leading edges of the arcs. The large ionospheric electric fields (250 mV m?1) found from tristatic radar measurements are evidence of strong currents associated with the region close to the optical arcs. The different data sets indicate that the arcs appear on the boundaries between regions with different average energy of diffuse precipitation, caused by pitch-angle scattering. The two thin arcs on these boundaries are found to be related to an increase in number flux (and thus increased energy flux) without an increase in energy

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Accepted/In Press date: 27 September 2011
Published date: 4 October 2011
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 397228
URI: http://eprints.soton.ac.uk/id/eprint/397228
ISSN: 0992-7689
PURE UUID: 4c313017-49b3-40e9-82b1-d5a8a86de007
ORCID for D.K. Whiter: ORCID iD orcid.org/0000-0001-7130-232X

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Date deposited: 24 Jun 2016 11:05
Last modified: 15 Aug 2019 00:41

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