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Interplanetary magnetic field control of theta aurora development
KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
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2002 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, no A7Article in journal (Refereed) Published
Abstract [en]

[1] We ascertain the influence of the B-y component of the interplanetary magnetic field (IMF) on theta aurora evolution. During most cases where a transpolar arc is observed to move across the polar region, and form a theta aurora, there are brief (minutes) southward excursions of IMF B-z, however northward IMF is required prior to theta aurora formation. Observations show that theta aurora can form during strictly northward IMF with its motion consistent with a change in sign of IMF B-y. It is important to note that since transpolar arcs can persist for 20-30 min after the IMF turns southward, errors will occur in assigning instantaneous IMF conditions to snapshots'' of particular auroral patterns. We consider the entire evolution of the theta aurora and the changing IMF conditions. The influence of IMF B-y is best illustrated by examples which occur during steady northward IMF as compared to times when the IMF is northward on average. We show examples, provided by the Polar UV imager, when the IMF is steady northward. For one case, DMSP F13 and F14 provide in situ measurements of precipitating particles, ionospheric plasma flows and ion density. This unique data set enables us to analyze in detail the evolution of a theta aurora, in one case crossing the entire polar region. No sign change in B-z is needed for theta aurora formation.

Place, publisher, year, edition, pages
2002. Vol. 107, no A7
Keyword [en]
auroral ionosphere, plasma convection, magnetosphere/ionosphere interactions, polar-cap, transpolar arcs, northward, dynamics, pattern, model, times, wind, imf
National Category
Fusion, Plasma and Space Physics
URN: urn:nbn:se:kth:diva-22013DOI: 10.1029/2001ja009126ISI: 000178982500042OAI: diva2:340711
QC 20100525 NR 20140804Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2012-03-19Bibliographically approved

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Cumnock, J. A.Blomberg, Lars G.
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