Terrestrial Ionospheric Signatures of Field-Aligned Currents

  1. C. T. Russell,
  2. E. R. Priest and
  3. L. C. Lee
  1. E. Friis-Christensen

Published Online: 21 MAR 2013

DOI: 10.1029/GM058p0605

Physics of Magnetic Flux Ropes

Physics of Magnetic Flux Ropes

How to Cite

Friis-Christensen, E. (1990) Terrestrial Ionospheric Signatures of Field-Aligned Currents, in Physics of Magnetic Flux Ropes (eds C. T. Russell, E. R. Priest and L. C. Lee), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM058p0605

Author Information

  1. Division of Geophysics, Danish Meteorological Institute, Lyngbyvej 100 DK-2100, Copenhagen, Denmark

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1990

ISBN Information

Print ISBN: 9780875900261

Online ISBN: 9781118663868



  • Solar photosphere;
  • Magnetic flux;
  • Astrophysics


Field-aligned currents play an important role in the magnetosphere and in particular in the physical processes involved in the coupling between the solar wind plasma and the Earth's magnetic field. The field-aligned currents consist of a large-scale part which is closely related to the solar wind magnetic fields and plasma. In addition to the large-scale part, a number of observations indicate the importance of small-scale field-aligned current filaments for the understanding of the magnetospheric plasma processes. Based on extensive magnetic field measurements collected by low altitude satellites, the large-scale field-aligned currents have been relatively well described. It is, however, considerably more difficult to deduce small-scale field-aligned currents from single satellite magnetic field observations. Since, however, the field-aligned current filaments close in the ionosphere, they will set up ionospheric currents, which may be observed by using ground-based magnetometers. With measurements of good spatial and temporal resolution it is possible to observe the ionospheric distribution and motion of the field-aligned current filaments. One type of field-aligned current filaments observed in this way corresponds to a pair of oppositely directed current fillaments moving primarily tailward along the auroral oval in the ionospheric projection of the dayside polar cleft. Since the cleft is associated with the low-latitude boundary layer of the magnetosphere, the presence of these field-aligned current filaments is probably a manifestation of boundary layer processes associated with reconfigurations of the magnetosphere due to sudden changes in the solar wind.