Models of normal and inverse polarity filament eruptions and coronal mass ejections

Abstract

An important problem in contemporary solar research is the relation between flares, filament eruptions, and coronal mass ejections (CMEs). Suppose that we take the viewpoint that flares, filament eruptions, and CMEs are all different aspects of the destabilization of a global magnetic configuration. In this case, to be successful a flare and filament eruption model such as that of Martens and Kuin (1989; hereafter MK) should not lead to predictions that contradict CME observations. We recount some observational properties. Hundhausen (1988) and Kahler (1988) note that CME structure often has three parts: a bright loop of enhanced density (1) encloses a dark region of depleted material (2) containing a bright core (3). They relate these satellite coronagraph observations to ground-based coronagraph and coronameter observations, and show that the bright loop is the initial overlying corona, the dark region is the prominence cavity, and the bright core is the erupting prominence. The basis of this association can be seen clearly in Figure 4 of Illing and Hundhausen (1985) which leads to the following inference. Since the difference in velocities between the bright loop's leading and trailing edges is much smaller than the difference in velocities between the loop's trailing edge and the bright core, the loop's transverse dimension (its thickness) increases much more slowly than does the depleted region or cavity dimension. Kahler (1988) states that the three-component model fits many, but not all observed CMEs. To explain the large fraction of CMEs that do exhibit this structure, a successful theory must not lead to more compression of material immediately above the prominence or filament than in the region of the bright loop. This requirement was compared with predictions for the MK flare-filament eruption model as extended by us. The field lines in this model with the values of the filament current and background dipole field as in MK are shown in Figure 1 for two different filament heights, H. Like MK, our results are zero-conductivity or infinite time plots; they assume that magnetic field evolution dominates compression or other effects, appropriate for a low beta coronal plasma. They are static equilibria and do not include dynamic effects. We shall be careful to clarify the effect of dynamics on our arguments. Suppose that we identify the innermost