Measuring Magnetic Helicity Transport in Solar Active Regions: a Practical Implementation

The causes of solar eruptions are not well understood, but it is clear that the emergence of magnetic flux and the accumulation of twisted (helical) magnetic fields in the solar atmosphere are preconditions for eruption. It has been very difficult to study these indicators because the magnetic data were unreliable due to varying `seeing' conditions. However, SOHO produces reliable magnetograms every 95 minutes. Chae (Astrophys. J. 560, L95, 2001) showed how SOHO (Solar and Heliospheric Observatory) data can yield reliable estimates of magnetic flux and magnetic helicity accumulation in the solar atmosphere. Chae's results suggest that regular time-series analyses of magnetograms could provide a useful early indicator of the build up of energy in the solar corona. Our objective has been to develop simple quantitative indicators of pre-eruption build-up and thereby warn of potential space weather related disturbances in space systems. We use the SOHO data, but in the near future the Solar B and SDO missions will provide much better magnetograms. So far, we have used Chae's method to map helicity transport in several regions with solar flares. We will show how advective helicity transport influences flare rate. We will also compare our results with analyses of vector magnetograms, which show both advective and convective helicity transport.