IMF dependence of high-latitude thermospheric wind pattern derived from CHAMP cross-track measurements

M. Förster, S. Rentz, W. Köhler, H. Liu, S. E. Haaland

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

Neutral thermospheric wind pattern at high latitudes obtained from cross-track acceleration measurements of the CHAMP satellite above both North and South polar regions are statistically analyzed in their dependence on the Interplanetary Magnetic Field (IMF) direction in the GSM y-z plane (clock angle). We compare this dependency with magnetospheric convection pattern obtained from the Cluster EDI plasma drift measurements under the same sorting conditions. The IMF-dependency shows some similarity with the corresponding high-latitude plasma convection insofar that the larger-scale convection cells, in particular the round-shaped dusk cell for ByIMF+ (ByIMF−) conditions at the Northern (Southern) Hemisphere, leave their marks on the dominant general transpolar wind circulation from the dayside to the nightside. The direction of the transpolar circulation is generally deflected toward a duskward flow, in particular in the evening to nighttime sector. The degree of deflection correlates with the IMF clock angle. It is larger for B yIMF+ than for ByIMF− and is systematically larger (∼5°) and appear less structured at the Southern Hemisphere compared with the Northern. Thermospheric cross-polar wind amplitudes are largest for BzIMF−/B yIMF− conditions at the Northern Hemisphere, but for BzIMF−/ ByIMF+ conditions at the Southern because the magnetospheric convection is in favour of largest wind accelerations over the polar cap under these conditions. The overall variance of the thermospheric wind magnitude at Southern high latitudes is larger than for the Northern. This is probably due to a larger "stirring effect" at the Southern Hemisphere because of the larger distance between the geographic and geomagnetic frameworks.

Original languageEnglish
Pages (from-to)1581-1595
Number of pages15
JournalAnnales Geophysicae
Volume26
Issue number6
DOIs
Publication statusPublished - Jun 11 2008
Externally publishedYes

Fingerprint

CHAMP
interplanetary magnetic fields
polar regions
magnetic field
Southern Hemisphere
convection
clocks
acceleration measurement
plasma drift
convection cells
plasma
atmospheric circulation
evening
polar caps
stirring
Northern Hemisphere
polar region
classifying
deflection
sorting

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Geology
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

IMF dependence of high-latitude thermospheric wind pattern derived from CHAMP cross-track measurements. / Förster, M.; Rentz, S.; Köhler, W.; Liu, H.; Haaland, S. E.

In: Annales Geophysicae, Vol. 26, No. 6, 11.06.2008, p. 1581-1595.

Research output: Contribution to journalArticle

Förster, M. ; Rentz, S. ; Köhler, W. ; Liu, H. ; Haaland, S. E. / IMF dependence of high-latitude thermospheric wind pattern derived from CHAMP cross-track measurements. In: Annales Geophysicae. 2008 ; Vol. 26, No. 6. pp. 1581-1595.
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