Causal Relations between Hα Loop Emergences and Soft X‐Ray Brightenings

Abstract

We compared high-resolution images of an emerging flux region in Hα and in soft X-ray, using two types of coalignments. Hα images were taken at Hida Observatory. Soft X-ray images were taken by the Soft X-ray telescope onboard Yohkoh. These data were obtained through coordinated observations by Hida Observatory and Yohkoh. Soft X-ray brightenings were found above most of the emerging Hα arch filaments, which are traces of rising magnetic flux tubes. The released energies in the soft X-ray brightenings were found to be ~1027 ergs, which is consistent with an estimate of energy release through magnetic reconnection between coronal fields and rising flux tubes as an Hα arch filament. These observational results indicate that an arch filament or rising magnetic flux tube itself is not heated up to coronal temperature as soon as it has reached coronal heights, but it can induce a change of magnetic structure through magnetic reconnection in the overlying corona. We also studied the structure of an arch filament in detail at its birth stage. Its morphological feature and evolutionary characteristics can be well explained by the asymmetric rising of a flux tube.