A Model of FTE Footprints in the Polar Cap

  1. C. T. Russell,
  2. E. R. Priest and
  3. L. C. Lee
  1. F. R. Toffoletto,
  2. T. W. Hill and
  3. P. H. Reiff

Published Online: 21 MAR 2013

DOI: 10.1029/GM058p0599

Physics of Magnetic Flux Ropes

Physics of Magnetic Flux Ropes

How to Cite

Toffoletto, F. R., Hill, T. W. and Reiff, P. H. (1990) A Model of FTE Footprints in the Polar Cap, 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/GM058p0599

Author Information

  1. Department of Space Physics and Astronomy, Rice University, Houston, TK 77251-1892

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


We have investigated the mapping of FTE's onto the polar cap ionosphere using the closed magnetic field model of Voigt [1981] and the perturbed (open) version of that model by Toffoletto and Hill [1989]. We have assumed that the magnetic flux associated with the FTE's crosses the magnetopause through small regions of large normal component, and that these small flux tubes map down to the polar cap ionosphere. This procedure essentially follows that of Crooker and Siscoe [1988], using a more realistic magnetopause and internal field model. In agreement with Crooker and Siscoe, we find that the footprint of a circular hole in the magnetopause of an otherwise closed magnetosphere becomes increasingly distorted as the hole moves from the day side to the night side. However, a similar region of enhanced open flux in an otherwise open magnetosphere maintains an approximately circular footprint. The first case, representing the hypothesis that magnetopause merging is an intrinsically sporadic process, results in a polar cap constructed from a scattered distribution of FTE's at the magnetopause. The second case, representing the hypothesis that FTE's are formed by sudden localized enhancements of merging along an already active quasisteady-state merging line, results in an open polar cap dotted with FTE footprints. Such regions moving through the ionosphere at a different rate than the background, would produce the dipolar electric-field and current structures predicted by Southwood [1987] and observed by Bering et al. [1988] and Lockwood et al. [1989].