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Seasonal dependence and solar wind control of transpolar arc luminosity
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.ORCID iD: 0000-0003-1270-1616
2008 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, no A8Article in journal (Refereed) Published
Abstract [en]

The influence of the solar wind and the interplanetary magnetic field (IMF) on the luminosity of transpolar arcs (TPAs) is examined by taking into account seasonal effects. The study focuses on those transpolar arcs that appear after an IMF By sign change during steady northward IMF. It includes 21 northern hemisphere events identified in a previous study from global UV images taken by the Polar spacecraft between 1996 and 2000. Sorting the TPA events by sign of the Earth dipole tilt we find that the TPAs which appear in the dark hemisphere are on average much weaker than TPAs in the sunlit hemisphere. For the dark hemisphere events, no clear correlation between solar wind parameters and TPA luminosity is found. However, in the sunlit hemisphere, a clear dependence on solar wind and IMF conditions is seen. The TPA brightness is strongly influenced by IMF magnitude, northward IMF Bz and solar wind speed. A weak, negative correlation with the ion density is found. The TPA luminosity in the sunlit hemisphere is much more strongly controlled by the magnetic energy flux than by the kinetic energy flux of the solar wind. This explains the absence of transpolar arcs for the two By sign change cases for positive dipole tilts with lowest magnetic energy flux values. The strong influence of the Earth dipole tilt on the transpolar arc luminosity appears due to the dependence of the ionospheric conductivity on solar EUV emissions.

Place, publisher, year, edition, pages
2008. Vol. 113, no A8
Keyword [en]
interplanetary magnetic-field, polar auroral arcs, theta-aurora, ultraviolet imager, northward imf, cap arcs, magnetosphere, emissions, precipitation, brightness
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-17791DOI: 10.1029/2008ja013086ISI: 000258824700004Scopus ID: 2-s2.0-55849129291OAI: oai:DiVA.org:kth-17791DiVA: diva2:335836
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-03-19Bibliographically approved

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