Subsurface characteristics of sunspots

Time-distance helioseismology provides 3-D subphotospheric maps of sunspots, emerging magnetic structures and associated convective flows. This gives us new insights into the basic physical processes inside the Sun, formation of magnetic structures in the solar plasma and mechanisms of solar activity. Recent results from the MDI instrument on SOHO reveal complicated stratification and flow patterns of solar plasma beneath sunspots, with a characteristic temperature increase in deeper layers and multiple vortex systems, providing evidence for a cluster model of sunspots. The helioseismic observations provide important clues for understanding the mechanisms of the formation of sunspots and active regions, and the subphotospheric dynamics of convective flows shearing and twisting magnetic fields in the corona. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.