Dynamics of solar coronal loops

Abstract

Observations in X-ray and EUV of the solar corona reveal the existence of very complex and dynamic structures made of plasma magnetically confined in loops. These structures can be studied by means of one-dimensional hydrodynamical loop models. Here we use a Lagrangian-remap code to simulate the dynamics of solar coronal loops with the purpose of quantifying the effects of varying the initial distribution of energy along the loop, the amount of input heating ( h 0 ), the total loop length ($2L$) and including/excluding the solar gravity term. In particular, the model calculations with no gravity are compared with the results obtained from previous isobaric, time-dependent models. Using a heat function that depends on distance along the loop and temperatures at the base of the loop typical of the solar corona, we find that in the non-gravity cases the plasma is allowed to cool down to chromospheric temperatures only when the decay length of the heating is below a certain critical value ($s_{H}/L=0.043$). For the same initial parameters, the inclusion of gravity produces final equilibrium states which are considerably hotter than those obtained when gravity is neglected and lowers the critical value of the decay length of the heating for which a cool condensation forms. In all cases, the outcome of the evolution can be predicted by a diagnostic diagram which describes the location of possible solutions for thermal equilibrium models.