In this paper, we investigate the 2D singular points and their relevant features in an emerging flux region (NOAA 7321) directly from the observed transverse field on October 27, 1991. Based on a constant- field model, we compare the 2D singular features in the observed field with those in the computed field. The 3D extrapolated field-line connectivity patterns are taken to confirm the relationship between these 2D features and the separatrices. With these results, we explore the role of the inferred separatrices in the heating of SXR loops in the coronal events. Our main conclusions are summarized as follows:
The filtering technique is proven efficient in removing the effect of measurement noises on the determination of 2D singular points, but trivial in changing the large-scale magnetic structures of interest. Moreover, the 2D field line patterns of connectivity can serve as a reference to confirm the 2D singular features.
The distributions of singular points in the observed field and the involved lanes are distinctly different from those in the inferred field. The 2D topology of the observed field shows more characters than those the linear force-free field can interpret. The cells bearing the different values suggest that they are involved in the magnetic fluxes of different origins.
The 2D cells can be grouped into L and H types in the light of the difference of 2D field-line connectivity patterns. They are respectively associated with two kinds of magnetic loops of the different heights and shapes.
An 1N/M1.1 flare and some small events show that the SXR bright loops are interacting where the inferred separatrices are located. This implies that magnetic reconnection may play a role in the heating of these SXR loops.
© European Southern Observatory (ESO) 1999
Online publication: February 23, 1999