Solar illumination control of ionospheric outflow above polar cap arcs

Maes, L., Maggiolo, R., De Keyser, J., Dandouras, I., Fear, R.C., Fontaine, D. and Haaland, S. (2015) Solar illumination control of ionospheric outflow above polar cap arcs Geophysical Research Letters, 42, (5), pp. 1304-1311. (doi:10.1002/2014GL062972).


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We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between ?94° and ?107°, with the O+ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O+ upflow occurs locally above the polar ionosphere. The same is found for H+, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conductivity.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1002/2014GL062972
ISSNs: 0094-8276 (print)
Organisations: Astronomy Group
ePrint ID: 394178
Date :
Date Event
12 February 2015Accepted/In Press
12 March 2015Published
Date Deposited: 12 May 2016 11:24
Last Modified: 09 Jun 2017 10:32
Further Information:Google Scholar

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