Astron. Astrophys. 324, 763-769 (1997)

Chromospheric polarity reversals on sunspots

Are they consistent with weak line emission?

J. Sánchez Almeida

Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain

Received 8 November 1996 / Accepted 10 February 1997

Abstract

Photospheric and chromospheric solar magnetograms sometimes show opposite polarity. This intriguing phenomenon is associated with the emergence of magnetic flux and with nearby, but not necessarily superposed, flaring activity. Despite the fact that there may be different explanations, it is shown here that the observed reversals are consistent with weak flare-like line emission all over the reversed polarity regions. Although this emission does not show up as a flare in filtergrams, it exhibits itself as a polarity reversal of the chromospheric magnetograms. If this interpretation were correct, the reversal would not correspond to a real flip of the magnetic field direction from the photosphere to the chromosphere. It would be an artifact due to radiative transfer effects. Observations to support or discard this hypothesis are briefly pointed out.

Key words: line: profiles polarization Sun: chromosphere Sun: flares Sun: magnetic fields sunspots

Send offprint requests to: J. Sánchez Almeida

Contents

• 1. Introduction
  • 1.1. Summary of observations concerning the CAZJ-reversal
• 2. The model polarity reversal
  • 2.1. Synthetic filtergrams and magnetograms
• 3. Comparison of the model reversal with observations
• 4. Wind-up and test
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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