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T. R. Metcalf (LMSAL), L. Fletcher (LMSAL/Glasgow), D. Alexander (LMSAL), D. S. Brown (U. St. Andrews), L. A. Ryder (UCD)
Based on a multi-wavelength data set and a topological model for the magnetic field, we argue that a M1.9 flare which occurred on 3-May-99 shows evidence of 3-d reconnection through a coronal null. Images from the Transition Region and Coronal Explorer allow the detailed examination of the structures involved in the flare and pre-flare in the 171Å~ (1MK) EUV passband, and the Lyman \alpha (10,000-20,000K) passband. Yohkoh Hard X-ray Telescope maps the position of non-thermal electron precipitation and the Soft X-ray Telescope reveals pre-flare and flare heating on large and small-scales. While the flare appears to trigger in small scale field close to the photosphere, near the interface between strong opposite magnetic polarities, the large-scale field is directly involved in or affected by all phases of the flare. We demonstrate how this observed activity on large and small scales, along with many other aspects of the flare find a qualitative explanation in the three-dimensional reconfiguration of coronal magnetic field, following a small-scale flux cancelation at the photosphere.
This work is supported by the TRACE and SXT projects at LMSAL (contract NAS5-38099 and NAS8-40801).