Abstract
One of the main aims of SOHO is to try and determine how the solar corona is heated. Here we first of all propose answers to the questions: why do some loops have a higher pressure than others and how are they contained? Then we summarise the main theories that have been proposed to heat the corona by waves, by reconnection in current sheets or by MHD turbulence, and in particular give some new results on the signature of braiding. Advances in solving the coronal heating problem are described, including the realisations that: most x-ray bright points are heated by driven reconnection (the converging flux model); Yohkoh observations suggest that loops are heated by two distinct mechanisms, namely an impulsive mechanism (probably reconnection) and a steadier background mechanism. Finally, a new technique is proposed for identifying the form of the heating mechanism, namely comparing observations of the temperature structure with loop models having different heating forms. This is a spur to theorists to deduce the form of heating produced by different models and to observers to determine temperature profiles with high accuracy. Applied to the large-scale diffuse corona as observed by Yohkoh, this technique implies that the heating is likely to be uniformly distributed along a loop: unless Alfvén waves can heat uniformly, the evidence is therefore in favour of turbulent microflare heating.
Original language | English |
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Pages (from-to) | 93-102 |
Number of pages | 10 |
Journal | European Space Agency, (Special Publication) ESA SP |
Issue number | 404 |
Publication status | Published - 1997 |
Keywords
- Corona
- Magnetic fields
- Reconnection