Astron. Astrophys. 356, 301-307 (2000)

Consistent determination of quasi force-free magnetic fields from observations in solar active regions

R. Berton

Observatoire de Paris, DASOP, 92195 Meudon Principal Cedex, France

Received 11 January 1999 / Accepted 10 November 1999

Abstract

The classical concept of extrapolating the photospheric magnetic field from line-of-sight measurements assuming a pure force-free field is revisited and a new procedure is proposed which is based on:

1. non-vanishing magnetic forces,

2. known horizontal forces from direct measurement of pressure or a related quantity (continuum brightness),

3. a small perturbation to the potential or linear force-free field which matches the distribution.

Orders of magnitude are estimated from observational data and they show that magnetic forces should be actually as large as expected from dimensional analysis.

Key words: Sun: activity Sun: magnetic fields

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Radiative model
• 3. Perturbation method
  • 3.1. Initial potential field
  • 3.2. Initial force-free field
• 4. Discussion
• Appendices
  • A: components of and with respect to
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: March 28, 2000
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