Statistical altitude distribution of Cluster auroral electric fields, indicating mainly quasi-static acceleration below 2.8 R-E and Alfvenic above
2014 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 119, no 11, 8984-8991 p.Article in journal (Refereed) Published
Results are presented from a statistical study of high-altitude electric fields and plasma densities using Cluster satellite data collected during 9.5years between 2 and 4 R-E. The average electric fields are most intense on the nightside and associated with an extensive plasma density cavity, with densities of 1cm(-3) or less. The intense electric fields are concentrated in two regions, separated by an altitude gap at about 2.8 R-E. Below this, the average electric field magnitudes reach about 50mV/m (mapped to the ionosphere) between 22 and 01 magnetic local time (MLT). Above 3 R-E, the fields are about twice as high and spread over a broader MLT range. These fields occur in a region where the (E/B)/V-A ratio is close to unity, which suggests an Alfvenic origin. The intense low-altitude electric fields are interpreted to be quasi-static, associated with the auroral acceleration region. This is supported by their location in MLT and altitude, and by a (E/B)/V-A ratio much below unity. The local electric field minimum between the two regions indicates a partial closure of the electrostatic potentials in the lower region. These results show similarities with model results of reflected Alfven waves by Lysak and Dum (1983), and with the O-shaped potential model, with associated wave-particle interaction at its top, proposed by Janhunen et al. (2000).
Place, publisher, year, edition, pages
2014. Vol. 119, no 11, 8984-8991 p.
quasi-static acceleration, Alfvénic acceleration, Statistical study, auroral electric fields
Other Physics Topics
IdentifiersURN: urn:nbn:se:kth:diva-155703DOI: 10.1002/2014JA020225ISI: 000346792100019OAI: oai:DiVA.org:kth-155703DiVA: diva2:761994
FunderSwedish National Space Board
QC 201501302014-11-102014-11-102015-01-30Bibliographically approved