On Magnetic Flux Imbalance in Solar Active Regions

Abstract

The magnetic flux imbalance of active regions has been studied using the longitudinal magnetograms obtained from the National Solar Observatory at Kitt Peak. The maximum and the median value of the flux imbalance in 137 active regions situated near the disk center is found to be about 62% and 9.5%, respectively. The detailed analysis of a few selected active regions shows that the local flux asymmetry is compensated on global scales. For example, the NOAA Active Region 7978, which appeared during the solar activity minimum period and evolved during five solar rotations (1996 July-October), shows a flux imbalance of about 9.5%, with an excess of following negative flux. However, on a global scale, the positive and negative flux in the entire solar disk was found to be nearly balanced during the same period. The global flux imbalance of the Sun during a full magnetic cycle is estimated from the Carrington maps. These maps are made by merging the solar images obtained during a complete solar rotation (about 27 days), hence each represents the entire surface of the Sun. The 10°-40° active latitudinal zone in the individual hemispheres during the solar maximum shows a flux imbalance of more than 20%. This is reduced to below 10% when the entire Sun is considered. The present study indicates that a fraction of the magnetic field from the localized active regions connects with far away locations.