Current and Kinetic Helicity of Long-Lived Activity Complexes

Abstract:

We focus on long-lived activity complexes and their helicity below and above the solar surface. These locations of recurrent flux emergence in or close to a pre-existing active region, last for typically five to seven solar rotations. It is known that emergence of new magnetic flux in pre-existing magnetic region causes an increase in topological complexity of the magnetic field which leads to flares and Coronal Mass Ejections (CMEs). A quantitative measure of topological complexity of magnetic fields is given by the magnetic helicity which measures twisting and linking of the magnetic field. The current helicity determined from vector magnetograms is the equivalent of the kinetic helicity determined from subsurface flows. The helicity is thus an ideal quantity to investigate the linkage of magnetic fields in the solar atmosphere with flows in the upper solar convection zone. The subsurface flows from the surface to a depth of 16 Mm are determined with a ring-diagram analysis of GONG and SDO/HMI Dopplergrams and the current helicity density is determined from SOLIS vector magnetograms. We will study the kinetic and current helicity as a function of time and Carrington longitude, averaged over a suitable range of latitudes in either hemisphere. We will present the latest results.