A study of the north-south asymmetry of sunspot area during solar cycle 23

S. R. Habbal1*, H. Morgan1 and M. Druckmüller2
1Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, USA
2Brno University of Technology, Technik´a 2, 616 69 Brno, Czech Republic

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We show how the complement of white light and a suite of Fe coronal forbidden line images taken during total solar eclipses since 2006 have yielded new insights into the physical properties of the coronal plasma and the role of the magnetic field. The unique properties of these spectral lines make them ideal diagnostic tools for exploring the first few solar radii above the photosphere where the expansion of the corona and the acceleration of the solar wind occur. In particular, these observations show how: (1) localized enhancements of the ion densities relative to electrons appear in some magnetic structures, (2) the transition between a collisiondominated to a collisionless plasma occurs within a heliocentric distance of 1.2 - 1.6 Rs, (3) the expanding corona is characterized by an electron temperature of 106 K, and (4) prominences are enshrouded by hot 2 × 106 K coronal plasma. We discuss the implications of these observations for the source and acceleration of the solar wind.

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Keywords : Sun: corona – solar wind – eclipses