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Small and meso-scale properties of a substorm onset auroral arc
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2010 (Engelska)Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, s. A10209-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present small and meso-scale properties of a substorm onset arc observed simultaneously by the Reimei and THEMIS satellites together with ground-based observations by the THEMIS GBO system. The optical observations revealed the slow equatorward motion of the growth-phase arc and the development of a much brighter onset arc poleward of it. Both arcs showed the typical particle signature of electrostatic acceleration in an inverted-V structure together with a strong Alfven wave acceleration signature at the poleward edge of the onset arc. Two THEMIS spacecraft encountered earthward flow bursts around the times the expanding optical aurora reached their magnetic footprints in the ionosphere. The particle and field measurements allowed for the reconstruction of the field-aligned current system and the determination of plasma properties in the auroral source region. Auroral arc properties were extracted from the optical and particle measurements and were used to compare measured values to theoretical predictions of the electrodynamic model for the generation of auroral arcs. Good agreement could be reached for the meso-scale arc properties. A qualitative analysis of the internal structuring of the bright onset arc suggests the operation of the tearing instability which provides a 'rope-like' appearance due to advection of the current in the sheared flow across the arc. We also note that for the observed parameters ionospheric conductivity gradients due to electron precipitation will be unstable to the feedback instability in the ionospheric Alfven resonator that can drive structuring in luminosity over the range of scales observed.

Ort, förlag, år, upplaga, sidor
2010. Vol. 115, s. A10209-
Nationell ämneskategori
Astronomi, astrofysik och kosmologi
Identifikatorer
URN: urn:nbn:se:kth:diva-31618DOI: 10.1029/2010JA015537ISI: 000286992800010Scopus ID: 2-s2.0-77958119468OAI: oai:DiVA.org:kth-31618DiVA, id: diva2:406091
Anmärkning
QC 20110324Tillgänglig från: 2011-03-24 Skapad: 2011-03-21 Senast uppdaterad: 2017-12-11Bibliografiskt granskad

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Karlsson, Tomas

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Rymd- och plasmafysik
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Journal of Geophysical Research
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