Explosive chromospheric evaporation as an origin for X-ray ejections

We report new results of numerical simulations of the response of the chrom osphere to impulsive heating for the cases of powerful and weak nonstationa ry processes. During weak impulsive heating, the response of an atmosphere consisting of the chromosphere, transition region, and corona is characteri zed by the development of two, rather than one, rising flows. The origin of the additional flow at the coronal level is nonuniformity in the heating o f the outer atmosphere with height; the second flow arises when there is ap preciable energy release not only in the chromosphere, but also in the coro nal layers. This second flow can accelerate the process of filling flare lo ops with hot plasma and provides an origin for the small-scale ejections re cently observed at ultraviolet and X-ray wavelengths. We discuss the contri bution of the phenomena considered to the overall mass balance in the coron a.