One‐dimensional and Pseudo–Two‐dimensional Hydrodynamic Simulations of Solar X‐Ray Jets

Abstract

We present results of one-dimensional hydrodynamic simulations of the chromospheric evaporation produced by a microflare in a large-scale loop as a model of X-ray jets. The initial conditions of the simulations are based on the observations of X-ray jets. We deposit thermal energy (~1 × 1028 ergs) in the corona. The deposited energy is rapidly transported to the chromosphere by conduction, which heats the dense plasma in the upper chromosphere. As a result, the gas pressure is increased and drives a strong upflow of dense, hot plasma along the magnetic loop. We found the following features of evaporation in the results of our simulations: (1) the maximum temperature of the evaporating plasma is determined by the balance between the conductive flux and the heating flux; (2) the total mass of evaporating plasma is controlled by the balance between the conductive flux and enthalpy flux; (3) the relationship between the density neva, height of energy deposition sflare, and heating rate Fh is described as neva ∝ F/s; (4) the X-ray intensity along the evaporation-flow plasma decreases exponentially with distance from the footpoint, and that exponential intensity distribution holds from the early phase to the decay phase; (5) in the single-loop model, the temperature decreases with distance from the energy deposition site (on the other hand, a hot region is present in front of the evaporation front in the multiple-loop model); (6) we compare the physical parameters of the evaporation flow with the observations of the X-ray jet that occurred on 1992 September 3 and find that the physical parameters of evaporating plasma are similar to those of the Yohkoh-observed X-ray jet. Since these properties of the evaporation flow are similar to the observed properties of X-ray jets, we suggest that an X-ray jet is the evaporation flow produced by a flare near the footpoint of a large-scale loop. Furthermore, according to the X-ray intensity distribution along the evaporation flow, we suggest that a multiple-loop model based on the magnetic reconnection mechanism can reproduce the properties of an X-ray jet better than the single-loop model.