One-dimensional and pseudo-two-dimensional hydrodynamic simulations of solar X-ray jets

We present results of one-dimensional hydrodynamic simulations of the chrom ospheric evaporation produced by a microflare in a large-scale loop as a mo del of X-ray jets. The initial conditions of the simulations are based on t he observations of X-ray jets. We deposit thermal energy (similar to1 x 10( 28) ergs) in the corona. The deposited energy is rapidly transported to the chromosphere by conduction, which heats the dense plasma in the upper chro mosphere. As a result, the gas pressure is increased and drives a strong up flow of dense, hot plasma along the magnetic loop. We found the following f eatures 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 enthal py flux; (3) the relationship between the density n(eva), height of energy deposition s(flare), and heating rate F-h is described as n(eva) proportion al to F-h(4/7)/s(flare)(3/7); (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 d ecay phase; (5) in the single-loop model, the temperature decreases with di stance 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 observa tions 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 Yohko h-observed X-ray jet. Since these properties of the evaporation flow are si milar to the observed properties of X-ray jets, we suggest that an X-ray je t is the evaporation flow produced by a flare near the footpoint of a large -scale loop. Furthermore, according to the X-ray intensity distribution alo ng the evaporation flow, we suggest that a multiple-loop model based on the magnetic reconnection mechanism can reproduce the properties of an X-ray j et better than the single-loop model.