1. 学术报告：“Magnetic Field and Energy Evolution in a Major Active Region Observed by SDO/HMI” 时间：9月18日（星期二）下午3：00 地点：行政科研楼1514会议室 报告人：孙旭东（博士） 单位：美国斯坦福大学 题目：“Magnetic Field and Energy Evolution in a Major Active Region Observed by SDO/HMI” 摘要：Full-disk, high-cadence observations from the the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamic Observatory (SDO) now allow us to study the evolving magnetic field in solar active regions with great detail. Using a vector magnetogram series from SDO/HMI and a non-linear force-free extrapolation, we monitor the field and energy evolution in NOAA AR 11158, where the first X-class flare of Solar Cycle 24 took place. Several findings are as follows. 1) Fast flux emergence and shearing created a quadrupolar system. A substantial amount of electric current and free energy were concentrated near a low-lying sigmoidal filament channel. The inferred magnetic energy showed a sudden decrease during the X-class flare, which was enough to power the explosion. 2) The horizontal magnetic field in the AR core underwent fast, irreversible increase during the flare. As a result, the coronal field displayed a downward collapse motion, consistent with the "coronal implosion" conjecture. 3) A small bipole emerged on the northeastern side of AR led to a series of "homologous eruptions"; all ejecta followed a highly inclined trajectory. The phenomenon can be explained by an asymmetric structure with anisotropic magnetic pressure. A persisting coronal null point was found in the model and observation, which provides further evidence for our interpretation.

李勤秀 Posted at 2012-09-13 14:08 CST Last modified at 2012-09-13 14:16 CST Link to this poster Top