Sigmoidal structures observed in X-rays have been shown to be precursors to CMEs, existing in some cases for several days before an eruption (Sterling and Hudson 1997,ApJ,491,L55; Canfield et al, 1999, GRL, 26, 6, 627). While these S-shaped structures are most apparent in X-ray active region observations, they may be manifestations of a more general helical magnetic structure having observational signatures at other wavelengths. We will present preliminary results of a survey search for sigmoidal structures and other CME tracers in archived SOHO/CDS data for a series of active regions known to contain erupting sigmoidal structures in X-ray observations. We are particularly interested in determining the relative locations and temperatures of these tracers, and will see to what extent the data answers questions such as, if S shapes are observed at different wavelengths do they line up, or is there a spatial displacement and/or rotation of angle of S that corresponds with height/temperature variation ? How does the appearance of the region vary over the lifetime of the observed x-ray sigmoidal structure ? After an eruption, how much if any of the S shape remains, and at what spatial and spectral locations ? We will use the results of this comparison survey to consider what the implications are for the underlying magnetic field structure, and the location and variation of heating throughout it.
8th SOHO Workshop: Plasma Dynamics and Diagnostics in the Solar Transition Region and Corona
- Pub Date:
- October 1999