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Cluster multi-point observations of the auroral acceleration region
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , ix, 45 p.
Series
Trita-EE, ISSN 1653-5146 ; 2011:041
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-35500ISBN: 978-91-7415-999-8 (print)OAI: oai:DiVA.org:kth-35500DiVA: diva2:428851
Presentation
2011-05-31, AL seminarierum, Teknikringen 31, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20110701Available from: 2011-07-01 Created: 2011-07-01 Last updated: 2012-01-17Bibliographically approved
List of papers
1. Altitude Distribution of the Auroral Acceleration Potential Determined from Cluster Satellite Data at Different Heights
Open this publication in new window or tab >>Altitude Distribution of the Auroral Acceleration Potential Determined from Cluster Satellite Data at Different Heights
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2011 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 5, 055002- p.Article in journal (Refereed) Published
Abstract [en]

Aurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by electron beams hitting the upper atmosphere, after being accelerated by quasistatic electric fields at 1-2 RE altitudes, or by wave electric fields. Although aurora was studied by many past satellite missions, Cluster is the first to explore the auroral acceleration region with multiprobes. Here, Cluster data are used to determine the acceleration potential above the aurora and to address its stability in space and time. The derived potential comprises two upper, broad U-shaped potentials and a narrower S-shaped potential below, and is stable on a 5 min time scale. The scale size of the electric field relative to that of the current is shown to depend strongly on altitude within the acceleration region. To reveal these features was possible only by combining data from the two satellites.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-30986 (URN)10.1103/PhysRevLett.106.055002 (DOI)000286878500008 ()2-s2.0-79551585415 (Scopus ID)
Note
QC 20110317Available from: 2011-03-17 Created: 2011-03-07 Last updated: 2017-12-11Bibliographically approved
2. Spatiotemporal features of the auroral acceleration region as observed by Cluster
Open this publication in new window or tab >>Spatiotemporal features of the auroral acceleration region as observed by Cluster
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2011 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, no 12, A00K19- p.Article in journal (Refereed) Published
Abstract [en]

A pair of negative electric potential structures associated with inverted-V aurora is investigated using electric and magnetic field, ion and electron data from the Cluster spacecraft, crossing the auroral acceleration region (AAR) at different altitudes above the Northern hemisphere midnight auroral oval. The spatial and temporal development of the acceleration structures is studied, given the magnetic conjunction opportunity and the one minute difference between the Cluster spacecraft crossings. The configuration allowed for estimation of characteristic times of development for the two structures and of the parallel electric field and potential drop for the more stable one. The first potential structure had a width of similar to 80 km (projected to the ionosphere) and was relatively short-lived, developing in less than 40 s and decaying in one minute. The parallel potential drop increased between altitudes of 1.13 R(E) and 1.3 R(E), whereas the acceleration potential above 1.3 R(E) remained almost unchanged during that time. This intensification occurred mainly after the time when the associated upward current had reached its maximum value. The second structure had a width of similar to 50 km and was subject to an increase by a factor of 3 of the parallel potential drop below 1.3 R(E), during about 40 s, after which it remained rather stable for one minute or more. Similarly here, the acceleration potential above 1.3 R(E) remained roughly unchanged. For the more stable second structure, an average parallel electric field between 1.13 and 1.3 R(E) could be estimated (similar to 0.56 mV/m). The conductance along the flux tube was also stable for one minute or more.

Keyword
Aurora, Quasi-static potential structures, Magnetosphere-Ionospher interaction, field-aligned currents, FAC, auroral acceleration region, AAR
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-35499 (URN)10.1029/2011JA016505 (DOI)000297979400001 ()2-s2.0-83455201438 (Scopus ID)
Note
Updated from submitted to published. Previous title: Spatio-temporal features of the auroral acceleration region as observed by Cluster. QC 20120117Available from: 2011-07-01 Created: 2011-07-01 Last updated: 2017-12-11Bibliographically approved

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