Logotyp: till Uppsala universitets webbplats

uu.sePublikationer från Uppsala universitet
Ändra sökning
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary
Visa övriga samt affilieringar
2008 (Engelska)Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, nr 1, s. 87-105Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromso (66.6 degrees cgmLat) and Longyearbyen (75.2 degrees cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5 degrees cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 R-E mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H+ and O+ ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2 degrees during similar to 5 min. The beginning of the poleward motion of the PCB was associated with an intensification of the downward FAC at the boundary. We suggest that the downward FAC sheet at the PCB is the high-altitude counterpart of the Earthward flowing FAC produced in the vicinity of the magnetotail neutral line by the Hall effect (Sonnerup, 1979) during a short-lived reconnection pulse.

Ort, förlag, år, upplaga, sidor
2008. Vol. 26, nr 1, s. 87-105
Nyckelord [en]
ionosphere, auroral ionosphere, electric fields and currents, storms and substorms
Nationell ämneskategori
Fysik
Identifikatorer
URN: urn:nbn:se:uu:diva-149885ISI: 000253672400008OAI: oai:DiVA.org:uu-149885DiVA, id: diva2:405890
Tillgänglig från: 2011-03-24 Skapad: 2011-03-24 Senast uppdaterad: 2017-12-11Bibliografiskt granskad

Open Access i DiVA

Fulltext saknas i DiVA

Person

Vaivads, Andris

Sök vidare i DiVA

Av författaren/redaktören
Vaivads, Andris
Av organisationen
Institutet för rymdfysik, Uppsalaavdelningen
I samma tidskrift
Annales Geophysicae
Fysik

Sök vidare utanför DiVA

GoogleGoogle Scholar

urn-nbn

Altmetricpoäng

urn-nbn
Totalt: 537 träffar
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf