Large scale magnetic helicity flux estimated from MDI magnetic synoptic charts over the 23rd solar cycle

Shangbin Yang, yangshb@bao.ac.cn, National Astronomical Observatories, Chinese Academy of Sciences China
Zhang Hongqi, hzhang@bao.ac.cn, National Astronomical Observatories, Chinese Academy of Sciences

Abstract
To investigate the characteristics of large scale and long term evolution of magnetic helicity with solar cycles, we follow the method of Local Correlation Tracking (LCT) to estimate the magnetic helicity evolution over the 23rd solar cycle from 1996 to 2009 by using 795 MDI magnetic synoptic charts. The main results are following: The hemispheric helicity rule still holds in general, i.e. the injection of large-scale negative (positive) magnetic helicity dominates the northern (southern) hemisphere. The large scale magnetic helicity flux of solar disk changes from negative value at the beginning to positive value at the end in the 23rd solar cycle, while the net accumulated magnetic helicity tends to be negative in the period of between 1996 and 2009. The mean large scale magnetic helicity fluxes show the same sign in both hemispheres especially in around 2001 and 2005. Moreover, the global injection of magnetic helicity of the Sun is still an open question.