Dynamics and Heating of Chromospheres
Abstract
The chromosphere constitutes the lower part of the transition between the relatively cool photosphere and the extremely hot corona.Detailed observations show the chromosphere to be highly dynamic. Its complicated structure is due to the intricate interaction of the solar plasma with the pervasive magnetic field.
However the solar chromosphere is difficult to study. It lies just above the photosphere where the transitions from optically thick to thin occurs so that the convenient approximation of LTE no longer holds for the calculation of radiative energy transfer. Secondly it is the region where a transition from high to low plasma beta (the ration of gas pressure to magnetic pressure) occurs. In combination these two properties require us to employ full-blown radiation magneto-hydrodynamic simulations to fathom the complexities of the chromosphere. A lingering chromospheric question is the presence of cool material (with temperatures as low as 3700 K) that seems to be required by dark spectral lines due to vibration-rotation transitions of the CO molecule. No physical models at this time can adequately explain the simultaneous presence of this cool material and the omni-presence of chromospheric UV emission which requires high temperatures at similar altitude in the chromosphere.- Publication:
-
Stars as Suns : Activity, Evolution and Planets
- Pub Date:
- January 2004
- Bibcode:
- 2004IAUS..219..115K