A statistical study of the low-altitude ionospheric magnetic fields over the north pole of Venus

T. L. Zhang, W. Baumjohann, C. T. Russell, M. N. Villarreal, J. G. Luhmann, Teh Wai Leong

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Examination of Venus Express (VEX) low-altitude ionospheric magnetic field measurements during solar minimum has revealed the presence of strong magnetic fields at low altitudes over the north pole of Venus. A total of 77 events with strong magnetic fields as VEX crossed the northern polar region were identified between July 2008 and October 2009. These events all have strong horizontal fields, slowly varying with position. Using the superposed epoch method, we find that the averaged peak field is about 45 nT, which is well above the average ambient ionospheric field of 20 nT, with a full width at half maximum duration of 32 s, equivalent to a width of about 300 km. Considering the field orientation preference and spacecraft trajectory geometry, we conclude that these strong fields are found over the northern hemisphere with an occurrence frequency of more than 33% during solar minimum. They do not show a preference for any particular interplanetary magnetic field (IMF) orientation. However, they are found over the geographic pole more often when the interplanetary field is in the Venus orbital plane than when it is perpendicular to the orbital plane of Venus. The structures were found most frequently in the -E hemisphere, determined from the IMF orientation. The enhanced magnetic field is mainly quasi perpendicular to solar wind flow direction, and it is suggested that these structures form in the low-altitude collisional ionosphere where the diffusion and convection times are long.

Original languageEnglish
Pages (from-to)6218-6229
Number of pages12
JournalJournal of Geophysical Research A: Space Physics
Volume120
Issue number8
DOIs
Publication statusPublished - 1 Aug 2015

Fingerprint

low altitude
Venus (planet)
magnetic fields
Venus
ionospherics
Arctic region
Poles
poles
Magnetic fields
magnetic field
interplanetary magnetic fields
spacecraft trajectories
Magnetic field measurement
orbitals
Solar wind
Ionosphere
Polar Regions
Northern Hemisphere
Full width at half maximum
hemispheres

Keywords

  • large magnetic fields
  • magnetic belts
  • Venusian ionosphere

ASJC Scopus subject areas

  • Space and Planetary Science
  • Geophysics

Cite this

A statistical study of the low-altitude ionospheric magnetic fields over the north pole of Venus. / Zhang, T. L.; Baumjohann, W.; Russell, C. T.; Villarreal, M. N.; Luhmann, J. G.; Wai Leong, Teh.

In: Journal of Geophysical Research A: Space Physics, Vol. 120, No. 8, 01.08.2015, p. 6218-6229.

Research output: Contribution to journalArticle

Zhang, T. L. ; Baumjohann, W. ; Russell, C. T. ; Villarreal, M. N. ; Luhmann, J. G. ; Wai Leong, Teh. / A statistical study of the low-altitude ionospheric magnetic fields over the north pole of Venus. In: Journal of Geophysical Research A: Space Physics. 2015 ; Vol. 120, No. 8. pp. 6218-6229.
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