MAGNETIC RECONNECTION ASSOCIATED WITH EMERGING MAGNETIC-FLUX

Two-dimensional (2D) magnetohydrodynamic (MHD) numerical simulations have been performed in order to study magnetic reconnection between an emerging flux and an overlying coronal magnetic field, while taking into account the effect of gravity, high spatial resolution, and a sufficient time span. The reconnection starts when most of the chromospheric mass in the current sheet between the emerging flux and the coronal field has drained down along the loop due to gravity. This implies that the start of a compact flare, or an X-ray bright point, follows the disappearance of an arch filament. It is also found that multiple magnetic islands are created in the sheet, which confine a cool, dense chromospheric plasma. These islands dynamically coalesce with each other and are ejected along the sheet at the Alfven speed. To check whether these phenomena occur in association with emerging flux would be an interesting subject for a cooperative study between optical and soft X-ray observations using the Yohkoh (Solar A) satellite.