Both in solar regions of strong (100-1000 gauss) magnetic field (active regions) and in regions of weaker field (quiet regions), filaments of chromospheric material reside in and trace out sheared magnetic fields over magnetic inversion lines. Such filaments, and hence the sheared fields that they trace, often erupt in flares and coronal mass ejections. The basic character of the eruption appears to be expansion and untwisting of the flux tube in which the erupting filament is embedded (Figure i). This paper focuses on the decrease of magnetic energy in this flux tube as the tube erupts. The dependence of the energy on the field expansion and untwisting is given for a simple model flux tube; this is used with estimates of the field expansion and decrease in twist in observed erupting filaments to empirically evaluate the energy decrease. This evaluation is made for three observed eruptive events: a small confined filament-eruption flare, a coronal mass ejection from the eruption of a large quiescent filament without a flare, and a large filament-eruption flare in which the filament was probably ejected in a spray and coronal mass ejection. The estimated decrease in magnetic energy is compared with the total released energy estimated from the observed magnitude of the flare in H-alpha and X-rays or from the observed mechanical energy of the mass ejection. In each case, the estimated decrease in magnetic energy is of the order of the total energy released. This result suggests the following:
1.Both in filament-eruption flares and in coronal mass ejections from filament eruptions, the basic drive is magnetic energy shedding by the filament-field eruption.
- Confined filament-eruption flares, filament-eruption flares with sprays and coronal mass ejections, and coronal mass ejections from quiescent filament eruptions are all events of the same kind.
ACKNOWLEDGEMENT.