Enhanced Acoustic Emission in Relation to the Acoustic Halo Surrounding Active Region 11429

Abstract

The use of acoustic holography in the high-frequency $p$-mode spectrum can resolve the source distributions of enhanced acoustic emissions within halo structures surrounding active regions. In doing so, statistical methods can then be applied to ascertain relationships with the magnetic field. This is the focus of this study. The mechanism responsible for the detected enhancement of acoustic sources around solar active regions has not yet been explained. Furthermore the relationship between the magnetic field and enhanced acoustic emission has not yet been comprehensively examined. We have used vector magnetograms from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) to image the magnetic-field properties in the halo. We have studied the acoustic morphology of an active region, with a complex halo and “glories”, and we have linked some acoustic properties to the magnetic-field configuration. In particular, we find that acoustic sources are significantly enhanced in regions of intermediate field strength with inclinations no different from the distributions found in the quiet Sun. Additionally, we have identified a transition region between the active region and the halo, in which the acoustic-source power is hindered by inclined fields of intermediate field strength. Finally, we have compared the results of acoustic-emission maps, calculated from holography, and the commonly used local acoustic maps, finding that the two types of maps have similar properties with respect to the magnetic field but lack spatial correlation when examining the highest-powered regions.