Presentation #102.06 in the session Coronal Heating: Present Understanding and Future Progress I.
The brightness of the emission from coronal loops in the solar atmosphere is strongly dependent on the temperature and density of the confined plasma. After a release of energy, these loops undergo a heating and upflow phase, followed by a cooling and downflow cycle. Throughout, there are significant variations in the properties of the coronal plasma. In particular, the increased coronal temperature leads to an excess downward heat flux that the transition region (TR) is unable to radiate. This generates an enthalpy flux from the TR to the corona, increasing the coronal density. The enthalpy exchange is highly sensitive to the TR resolution in numerical simulations. With a numerically under-resolved TR, major errors occur in simulating the coronal density evolution and, thus, the predicted loop emission. We present a new method that addresses the difficulty of obtaining the correct interaction between the corona and corona/chromosphere interface. In the TR, an Adaptive Conduction method is used that broadens any unresolved parts of the atmosphere. I will show that this approach, referred to as TRAC, successfully removes the influence of numerical resolution on the coronal density response to heating while maintaining high levels of agreement with fully resolved models. A detailed analytical assessment of the TRAC method will also be presented to demonstrate why the approach works through all phases of an impulsive heating event.