Occurrence and properties of substorms associated with pseudobreakups
2010 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, A12310- p.Article in journal (Refereed) Published
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.
solar-wind, pseudo-breakup, auroral oval, polar-cap, convection, disturbances, ionosphere, dynamics, flows
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:kth:diva-28586DOI: 10.1029/2010JA015866ISI: 000285256000005ScopusID: 2-s2.0-78650258160OAI: oai:DiVA.org:kth-28586DiVA: diva2:388241
QC 201101172011-01-172011-01-172012-03-19Bibliographically approved