报告题目：Solar magnetic activity and space weather

报告人：Dr. Thomas Wiegelmann (德国马普太阳系所)

时间：7月2日，星期四，下午3点

地点：闻天楼南楼208

报告摘要：The source region of space weather events like flares and coronal mass ejections is in the solar corona. Due to the low plasma beta, these eruptions are driven by instabilities in the coronal magnetic field. Consequently a detailed knowledge of the 3D-structure and evolution of the solar coronal magnetic field is important for understanding coronal eruptions. Direct measurements of the coronal magnetic field are not routinely available, but in the solar photosphere the magnetic field vector is measured with high accuracy, e.g. ground based from SOLIS and space-born with SDO. Under suitable model assumptions, e.g. the force-free field assumption (the Lorentz-force vanishes), these measurements can be extrapolated to model the coronal magnetic field. The resulting 3D magnetic field models provide information relevant for space-weather events, e.g. the free magnetic energy and the occurrence of current sheets and flux ropes. Furthermore the coronal field models help to guide the analysis of coronal images and pectroscopic data.