Uncombed Penumbrae: Formation, Ongoing Reconnections and Fine Substructures

Sunspot penumbrae consist of an ``uncombed'' system of thin, interlaced magnetic flux tubes with varying physical parameters and inclinations. Recent high-resolution observations from space and ground based instruments reveal previously unobservable details in structure and dynamics of penumbra. Based on these observation we propose a mechanism that explains the fine structures of penumbra filaments, their dynamics and their formation process. The mechanism is based on the fact that the umbra itself is a dense conglomerate of twisted, interlaced flux tubes with peripheral filaments branching out from the ``trunk'' at different heights due to ongoing reconnection processes. The twist of individual filaments, and resulting distribution of magnetic fields and temperature forming sub-structure of filaments, is due to the onset of the post-reconnection screw pinch instability, the parameters and details of which are well observed and can be measured from our data.