2010 August 1-2 sympathetic eruptions: I. Magnetic topology of the source-surface background field

摘要

A sequence of apparently coupled eruptions was observed on 2010 August 1-2 bySDO and STEREO. The eruptions were closely synchronized with one another, eventhough some of them occurred at widely separated locations. In an attempt toidentify a plausible reason for such synchronization, we study the large-scalestructure of the background magnetic configuration. The coronal field wascomputed from the photospheric magnetic field observed at the appropriate timeperiod by using the potential field source-surface model. We investigate the resulting field structure by analyzing the so-calledsquashing factor calculated at the photospheric and source-surface boundaries,as well as at different coronal cross-sections. Using this information as aguide, we determine the underlying structural skeleton of the configuration,including separatrix and quasi-separatrix surfaces. Our analysis reveals, inparticular, several pseudo-streamers in the regions where the eruptionsoccurred. Of special interest to us are the magnetic null points and separatorsassociated with the pseudo-streamers. We propose that magnetic reconnectiontriggered along these separators by the first eruption likely played a key rolein establishing the assumed link between the sequential eruptions. The presentwork substantiates our recent simplified magnetohydrodynamic model ofsympathetic eruptions and provides a guide for further deeper study of thesephenomena. Several important implications of our results for the S-web model ofthe slow solar wind are also addressed.