IRIS-6: The Chromosphere

The chromosphere and its connections to the transition region and corona (Invited)

22 Jun 2016, 11:15

30m

FR4 (AlbaNova University Centre)

Session 5

Speaker

Hardi Peter (MPI for Solar System Research)

Description

There is an everlasting mass cycle between the chromosphere and the upper atmosphere, the transition region and the corona. Many suggestions have been made on the nature of this mass cycle, from handwaving arguments to 3D MHD models. However, each of these suggestions has its problems and it is unclear what really governs the mass exchange. For example the transition region emission in the quiet Sun seems to be dominated by spicule-type emission, and spicules are not (yet) well represented in 3D models. In active regions many of the cooler transition region structures seem to be present in the form of small dynamic cool loops and it remains to be seen how loops reaching coronal temperatures are actually connected to such cooler loops. Since long components in the profiles of transition region and coronal lines have been identified in particular in the blue wings, indicating upflows that might indicate the injection of plasma into the corona. But then the question remains unanswered if such upflows are sufficient to feed the corona with mass. Finally, when discussing the connection from the chromosphere to the transition region and corona one also has to consider the relation to the magnetic structure. While tiny loops in the network exist, these unresolved fine structures might not be the dominant source of emission in the transition region, which also is part of solving the puzzle that seemingly loop-like structures are found in unipolar magnetic regions. Here the connection of the transition region structures to the chromosphere might be closer than we think so far, and many of the elongated transition region structures might be closely related to the fibrils in the chromosphere. For these and other observations the data from IRIS have been contributing key information that hopefully will further help unraveling the complex interaction from the chromosphere to the transition region and corona.