In situ spatiotemporal measurements of the detailed azimuthal substructure of the substorm current wedge
2014 (English)In: Journal of Geophysical Research: Space Physics, ISSN 2169-9380, Vol. 119, no 2, 927-946 p.Article in journal (Refereed) Published
The substorm current wedge (SCW) is a fundamental component of geomagnetic substorms. Models tend to describe the SCW as a simple line current flowing into the ionosphere toward dawn and out of the ionosphere toward dusk, linked by a westward electrojet. We use multispacecraft observations from perigee passes of the Cluster 1 and 4 spacecraft during a substorm on 15 January 2010, in conjunction with ground-based observations, to examine the spatial structuring and temporal variability of the SCW. At this time, the spacecraft traveled east-west azimuthally above the auroral region. We show that the SCW has significant azimuthal substructure on scales of 100km at altitudes of 4000-7000km. We identify 26 individual current sheets in the Cluster 4 data and 34 individual current sheets in the Cluster 1 data, with Cluster 1 passing through the SCW 120-240s after Cluster 4 at 1300-2000km higher altitude. Both spacecraft observed large-scale regions of net upward and downward field-aligned current, consistent with the large-scale characteristics of the SCW, although sheets of oppositely directed currents were observed within both regions. We show that the majority of these current sheets were closely aligned to a north-south direction, in contrast to the expected east-west orientation of the preonset aurora. Comparing our results with observations of the field-aligned current associated with bursty bulk flows (BBFs), we conclude that significant questions remain for the explanation of SCW structuring by BBF-driven wedgelets. Our results therefore represent constraints on future modeling and theoretical frameworks on the generation of the SCW.
Place, publisher, year, edition, pages
2014. Vol. 119, no 2, 927-946 p.
Substorm current wedge, Field-aligned current, Wedgelets, Aurora, Magnetosphere, Earth
IdentifiersURN: urn:nbn:se:kth:diva-146159DOI: 10.1002/2013JA019302ISI: 000333041000021ScopusID: 2-s2.0-84911212804OAI: oai:DiVA.org:kth-146159DiVA: diva2:722502
QC 201406092014-06-092014-06-092014-06-09Bibliographically approved