Helicity of magnetic clouds and their associated active regions

Abstract

In this work we relate the magnetic and topological parameters of twelve interplanetary magnetic clouds to associated solar active regions. We use a cylindrically symmetric constant-α force-free model to derive field line twist, total current, and total magnetic flux from in situ observations of magnetic clouds. We compare these properties with those of the associated solar active regions, which we infer from solar vector magnetograms. Our comparison of fluxes and currents reveals: (1) the total flux ratios ΦMC/ ΦAR tend to be of order unity, (2) the total current ratios IMC/IAR are orders of magnitude smaller, and (3) there is a statistically significant proportionality between them. Our key findings in comparing total twists αL are that (1) the values of (αL) MC are typically an order of magnitude greater than those of (αL)AR and (2) there is no statistically significant sign or amplitude relationship between them. These findings compel us to believe that magnetic clouds associated with active region eruptions are formed by magnetic reconnection between these regions and their larger-scale surroundings, rather than simple eruption of preexisting structures in the corona or chromosphere. Copyright 2004 by the American Geophysical Union.