Investigation of surface effects of flux tubes in an artificially stabilized atmosphere
Matthias Waidele and Markus Roth
Leibniz-Institut für Sonnenphysik (KIS)
We use the SPARC code for MHD simulations with monolithic flux tubes of varying subsurface topology in an artificially stabilized atmosphere. Our studies involve the interactions of waves caused by a single source with subsurface magnetic fields. Mode conversion causing acoustic power to trickle downwards along the flux tube has been described before and can be visualized in our simulations. We show that this downward propagation causes the flux tube to act as an isolated source, creating a characteristic surface wavefield. Measuring this wavefield at the surface shows differences depending on the flux tube model. Using time distance helioseismology, we demonstrate how to detect such a flux tube signal based on a group travel-time delay of dt = 282.6 s due to the wave packet spending time subsurface as a slow mode wave. This kind of study has the potential to reveal subsurface information of sunspots based on the analysis of a surface signal, therefore helping in understanding the emergence and early evolution of active regions.