CMEs Associated with Eruptive Prominences: How to Predict?

Solar prominences can be viewed as pre-eruptive states of coronal mass ejections (CMEs). Eruptive prominences are the phenomena most related to CMEs observed in the lower layers of the solar atmosphere. The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fills the whole volume of the dark cavity stretched in the corona along the photospheric polarity inversion line. Cold dense prominence matter accumulates in the lower parts of helical flux tubes, which serve as magnetic traps in the gravitation field. Coronal cavity is rather inconvenient feature for observation owing to reduced emission, so prominences and filaments are the best tracers of the flux ropes in the corona long before the beginning of eruption. Thus, the problem of the CME prediction can be reduced to the analysis of the filament equilibrium and estimation of the stability store. The height of a prominence (or a filament when observed against the disk) increases with its age and the death of a filament is usually an eruption which is followed by a CME. The filament height, then, can be a measure of its age and its readiness for eruption. In inverse-polarity models the equilibrium height of a filament is related to the value of the filament electric current. The stronger the electric current, the greater the height of the filament. However, the equilibrium and stability of a filament depend not only on its current but also on the characteristics of the external magnetic field. In order to estimate the probability of eruption, we should therefore compare the observed prominence height with a value characterizing the photospheric magnetic field. This value is the critical height, which can be found in the distribution of the magnetic field vertical gradient above the polarity inversion line. We had analyzed three dozens of filaments and found that eruptive prominences were near the limit of stability a few days before eruptions. We believe that the comparison of the real heights of prominences with the calculated critical heights could be a basis for predicting filament eruptions and following CMEs.