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Intense high-altitude auroral electric fields: temporal and spatial characteristics
KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.ORCID iD: 0000-0003-1270-1616
KTH, Superseded Departments, Alfvén Laboratory.ORCID iD: 0000-0002-1594-1861
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2004 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, no 7, 2485-2495 p.Article in journal (Refereed) Published
Abstract [en]

Cluster electric field, magnetic field, and energetic electron data are analyzed for two events of intense auroral electric field variations, both encountered in the Plasma Sheet Boundary Layer (PSBL), in the evening local time sector, and at approximately 5 R-E geocentric distance. The most intense electric fields (peaking at 450 and 1600 mV/m, respectively) were found to be quasi-static, unipolar, relatively stable on the time scale of at least half a minute, and associated with moving downward FAC sheets (peaking at similar to10 muA/m(2)), downward Poynting flux (peaking at similar to35 mW/m(2)), and upward electron beams with characteristic energies consistent with the perpendicular potentials (all values being mapped to 1 R-E geocentric distance). For these two events in the return current region, quasi-static electric field structures and associated FACs were found to dominate the upward acceleration of electrons, as well as the energy transport between the ionosphere and the magnetosphere, although Alfven waves clearly also contributed to these processes.

Place, publisher, year, edition, pages
2004. Vol. 22, no 7, 2485-2495 p.
Keyword [en]
Magnetospheric physics (electric fields; auroral phenomena; magnetosphere-ionosphere interactions); electric field; magnetic field; magnetosphere
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-7556DOI: 10.5194/angeo-22-2485-2004ISI: 000223620300020Scopus ID: 2-s2.0-4344694040OAI: oai:DiVA.org:kth-7556DiVA: diva2:12619
Note
QC 20100730. Meeting on Spatio-Temporal Analysis and Multipoint Measurements in Space. Orleans, FRANCE. MAY 12-16, 2003 Available from: 2007-10-22 Created: 2007-10-22 Last updated: 2011-10-20Bibliographically approved
In thesis
1. Investigations of auroral electric fields and currents
Open this publication in new window or tab >>Investigations of auroral electric fields and currents
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The Cluster spacecraft have been used to investigate auroral electric fields and field-aligned currents (FACs) at geocentric distances between 4 and 7 Re. The electric fields have been measured by the EFW instrument, consisting of two pairs of spherical probes, and the FACs have been calculated from measurements of the magnetic field by the FGM fluxgate magnetometer. CIS ion and PEACE electron measurements have also been used. Event studies as well as statistical studies have been used to determine the characteristics of the auroral electric fields. In two events where regions of both spatial and temporal electric field variations could be identified, the quasi-static electric fields were, compared to the Alfvén waves, found to be more intense and contribute more to the downward Poynting flux. With the use of the four Cluster spacecraft, the quasi-static electric field structures were found to be relatively stable on the time scale of at least half a minute. Quasi-static electric fields were found throughout the altitude range covered by Cluster in the auroral region. The electric field structures were found both in the upward and downward current regions. Bipolar and monopolar electric fields, corresponding to U- and S-shaped potential structures, have been found at different plasma boundaries, consistent with the view that the plasma conditions and the geometry of the current system are related to the shape of the electric field. The type of the bipolar electric field structures (convergent or divergent) was further found to be consistent with the FAC direction. The typical scale sizes of the electric field structures have been determined to be between 4 and 5 km, when mapped to ionospheric altitude. The most intense FACs associated with intense electric fields were found for small FAC widths. The widths of upward and downward FACs were similar.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. vii, 48 p.
Series
Trita-EE, ISSN 1653-5146 ; 2007:056
Keyword
auroral physics, auroral electric fields, auroral potential structures, auroral particle acceleration
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-4512 (URN)978-91-7178-761-3 (ISBN)
Public defence
2007-11-09, F3, Lindstedsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100730Available from: 2007-10-22 Created: 2007-10-22 Last updated: 2010-07-30Bibliographically approved

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Karlsson, TomasMarklund, GöranLindqvist, Per-Arne

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