Occurrence rate of earthward-propagating dipolarization fronts
2012 (English)In: Geophysical Research Letters, ISSN 0094-8276, Vol. 39, L10101- p.Article in journal (Refereed) Published
The occurrence rate of earthward-propagating dipolarization fronts (DFs) is investigated in this paper based on the 9 years (2001-2009) of Cluster 1 data. For the first time, we select the DF events by fitting the characteristic increase in B-z using a hyperbolic tangent function. 303 earthward-propagating DFs are found; they have on average a duration of 4 s and a B-z increase of 8 nT. DFs have the maximum occurrence at Z(GSM) approximate to 0 and r approximate to 15 R-E with one event occurring every 3.9 hours, where r is the distance to the center of the Earth in the XYGSM plane. The maximum occurrence rate at Z(GSM) approximate to 0 can be explained by the steep and large increase of B-z near the central current sheet, which is consistent with previous simulations. Along the r direction, the occurrence rate increases gradually from r approximate to 20 to r approximate to 15 R-E but decreases rapidly from r approximate to 15 to r approximate to 10 R-E. This may be due to the increasing pileup of the magnetic flux from r approximate to 20 to r approximate to 15 R-E and the strong background magnetic field at r <similar to 13 R-E, where the magnetic field changes from the tail-like to dipolar shape. The maximum occurrence rate of DFs (one event per 3.9 hours) is comparable to that of substorms, indicating a relation between the two.
Place, publisher, year, edition, pages
2012. Vol. 39, L10101- p.
IdentifiersURN: urn:nbn:se:uu:diva-176232DOI: 10.1029/2012GL051784ISI: 000304560600004OAI: oai:DiVA.org:uu-176232DiVA: diva2:535232