On a Surge: Properties of an Emerging Flux Region

Abstract

A surge event with multi-instrument and multiwavelength observations is presented. The event occurred in a surge-productive region on 2001 August 30. TRACE white-light images, Huairou vector magnetograms, and Hβ filtergrams show that this surge was closely associated with new bipoles that emerged in 1 hr. Evidence of enhanced magnetic cancellation is revealed at the footpoints of the surge where a simultaneous surge flare is shown in the Hβ line. In particular, the interesting observational results for this surge are that (1) the surge was associated with pronounced photospheric bright points near the emerging spots; (2) in vector magnetograms, during the surge ascending period, reliable transverse fields appeared between the emerging flux and the ambient fields cancelled at the base of the surge, and these fresh transverse fields disappeared after 20 minutes; (3) the preceding spots of the emerged bipoles almost disappeared in white-light images when the surge activity stopped; and (4) the TRACE UV (1550 Å) channel showed a bright surge (∼10 5 K) well correlated with the dark Hβ surge (∼10 3-104 K). The UV surge had a bright spike shape and spouted out along the outer edges of the Hβ surge. Similarly, the bright components in TRACE EUV (∼106 K) were also located at the edges of the Hβ surge. Both the SOHO/EIT and Yohkoh/SXT observations demonstrate that the jet plasma was ejected from one footpoint of a flaring coronal loop identified during the surge. We estimate the magnetic energy released from the site of the magnetic cancellation, the kinetic energy of the surge, and the thermal energy for the loop brightening in SXR, finding that the magnetic reconnection could supply enough energy for the surge activities and the coronal loop heating. For this surge, all the correlated phenomena in multiwavelengths (Hβ, white light, UV, EUV, and SXR) are in good temporal and spatial relationship. These facts support a magnetic reconnection model in which surges originate in the low atmosphere. Moreover, low-altitude magnetic reconnections can result in the magnetic cancellation observed on the photosphere.