http://arxiv.org/abs/2209.10156
Recent observational and numerical studies show a variety of thermal structures in the solar chromosphere. Given that the thermal interplay across the transition region is a key to coronal heating, it is worth investigating how different thermal structures of the chromosphere yield different coronal properties. In this work, by MHD simulations of Alfv\'{e}n-wave heating of coronal loops, we study how the coronal properties are affected by the chromospheric temperature. To this end, instead of solving the radiative transfer equation, we employ a simple radiative loss function so that the chromospheric temperature is easily tuned. When the chromosphere is hotter, because the chromosphere extends to a larger height, the coronal part of the magnetic loop becomes shorter, which enhances the conductive cooling. A larger loop length is therefore required to maintain the high-temperature corona against the thermal conduction. From our numerical simulations we derive a condition for the coronal formation with respect to the half loop length $l_{\rm loop}$ in a simple form: $l_{\rm loop} > a T_{\rm min} + l_{\rm th}$, where $T_{\rm min}$ is the minimum temperature in the atmosphere and parameters $a$ and $l_{\rm th}$ have negative dependencies on the coronal field strength. Our conclusion is that the chromospheric temperature has a non-negligible impact on coronal heating for loops with small length and weak coronal field. In particular, the enhanced chromospheric heating could prevent the formation of the corona.
H. Washinoue, M. Shoda and T. Suzuki
Thu, 22 Sep 22
4/65
Comments: 18 pages, 19 figures, accepted for publication in ApJ