Magnetic Helicity in Emerging Active Regions: A Statistical Study

Liu Yang, yliu@sun.stanford.edu, Stanford University, United States
Team HMI, Stanford University

Abstract
Magnetic helicity in emerging active regions in early phase of solar cycle 24 is studied using HMI vector magnetic field data. Magnetic helicity in active-region corona is computed from the helicity flux across the photosphere, which is derived using the measured vector magnetic field on the photosphere and the velocity field computed from time-series vector magnetic field data using the algorithm DAVE4VM (Schuck 2008). The so-called ``hemisphere rule'' of magnetic helicity is examined. Relationship between solar transient and magnetic helicity in active regions is also explored here.