Large-Angle Spectrometric Coronagraph Measurements of the Energetics of Coronal Mass Ejections

We examine the energetics of coronal mass ejections (CMEs) with data from the large-angle spectrometric coronagraphs (LASCO) on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity, and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for several CMEs that exhibit flux-rope morphologies. Assuming flux conservation, we use observations of the magnetic flux in a variety of magnetic clouds near the Earth to determine the magnetic flux and magnetic energy in CMEs near the Sun. We find that the potential and kinetic energies increase at the expense of the magnetic energy as the CME moves out, keeping the total energy roughly constant. This demonstrates that flux-rope CMEs are magnetically driven. Furthermore, since their total energy is constant, the flux-rope parts of the CMEs can be considered a closed system above ~2 R_solar.