题 目：Measuring the magnetic energy and helicity in the emerging active regions with HMI vector magnetograms
报告人：Dr. Yang Liu (刘扬 博士)
(Stanford University)
摘 要：The magnetic energy and helicity in emerging active regions are calculated using the HMI vector magnetic field data and DAVE4 VM (Schuck 2008) technique. The active regions studied in the paper, from simple to complicated, are AR11072, AR11117 and AR11158. It is found that (1) in two active regions the sign of the helicity is against the hemisphere rule; (2) the helicity in the corona are predominantly contributed by the surface flows; (3) comparing with the emergence of magnetic flux, the helicity flux through the photosphere shows a slight delay in phase; (4) the energy and helicity fluxes due to surface flows are significant during emergence of magnetic flux, and become much smaller after the emergence stops, while the energy flux from the vertical flow is still significant. A discussion is also placed here.
时 间：2011年9月14日（星期三）上午9:30
地 点：（北京西路2号）紫台大楼517会议室
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