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Occurrence and properties of substorms associated with pseudobreakups
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.ORCID iD: 0000-0002-0349-0645
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.ORCID iD: 0000-0003-1270-1616
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
2010 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, A12310- p.Article in journal (Refereed) Published
Abstract [en]

We investigate how substorms with and without growth-phase pseudobreakups are affected by solar wind and ionospheric conditions. The study is based on 874 events identified with Polar UVI. An AE index analysis shows that substorms with growth-phase pseudobreakups are typically weak and appear as isolated events after hours of low geomagnetic activity. During the hours before onset the average solar wind merging field E-m is weaker, and the length of time with enhanced values shorter than for regular substorms. Integrating E-m over the last southward IMF period before onset shows an upper limit above which these substorms do not occur. To estimate how much E-m reaches the ionosphere, polar cap potential drop and unified PC indices are examined. It is found that substorms with growth-phase pseudobreakups have on average lower PC index values than regular substorms. The temporal evolution of the PC indices is similar for both substorm groups; the summer index correlates better with E-m, the winter index with AE. Also the average polar cap potential drop curves for both types of substorms resemble one other; the dayside and nightside curves are mainly influenced by E-m and AE, respectively. Comparing growth-phase, isolated and recovery pseudobreakups shows that solar wind and ionospheric conditions around the first substorm after a pseudobreakup are similar, independent of whether the last pseudobreakup appeared hours (recovery and isolated pseudobreakups) or minutes before substorm onset (growth-phase pseudobreakups). Isolated and recovery pseudobreakups are less often associated with a northward IMF rotation than growth-phase pseudobreakups or substorms.

Place, publisher, year, edition, pages
2010. Vol. 115, A12310- p.
Keyword [en]
solar-wind, pseudo-breakup, auroral oval, polar-cap, convection, disturbances, ionosphere, dynamics, flows
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-28586DOI: 10.1029/2010JA015866ISI: 000285256000005ScopusID: 2-s2.0-78650258160OAI: diva2:388241
QC 20110117Available from: 2011-01-17 Created: 2011-01-17 Last updated: 2012-03-19Bibliographically approved

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Kullen, AnitaKarlsson, TomasCumnock, Judy A.Sundberg, Torbjörn
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