Flaring loop motion and a unified model for solar flares

We performed 2.5-dimensional numerical simulations of magnetic reconnection for several models, some with the reconnection point at a high altitude (t he X-type point in magnetic reconnection), and one with the reconnection po int at a low altitude. In the high-altitude cases, the bright loop appears to rise for a long time, with its two footpoints separating and the field l ines below the bright loop shrinking, which are all typical features of two -ribbon flares. The rise speed of the loop and the separation speed of its footpoints depend strongly on the magnetic held B-0, to a medium extent on the density rho(0), and weakly on the temperature T-0, the resistivity n(0) , and the length scale L-0, by which the size of current sheet and the heig ht of the X-point are both scaled. The strong B-0, dependence means that th e Lorentz force is the dominant factor; the inertia of the plasma may accou nt for the moderate rho(0) dependence; and the weak n dependence may imply that "fast reconnection" occurs; the weak L-0 dependence implies that the f laring loop motion has geometrical self-similarity. In the low-altitude cas e, the bright loops cease rising only a short time after the impulsive phas e of the reconnection and then become rather stable, which shows a distinct similarity to the compact flares. The results imply that the two types of solar flares, i.e., the two-ribbon flares and the compact ones, might be un ified into the same magnetic reconnection model, where the height of the re connection point leads to the bifurcation.