Physics of Coronal Mass Ejections (CMEs): Theory and Observation

Solar eruptions are manifested as coronal mass ejections (CMEs), solar flares, and eruptive promi nences (EPs) depending on observing methods. The amount of energy released is estimated to be 1031–1033 erg. CMEs and EPs represent acceleration of magnetized coronal structures (1014–1016 g in mass) to a few thousand km/s in tens of minutes. The physical mechanisms responsible for these closely associated processes have been a major question in modern solar physics for more than half a century.  Observationally, the recent STEREO mission has yielded data on CME dy namics from the Sun to 1 AU, providing much more stringent constraints on CME models than previously available. The prevailing paradigm envisions releasing magnetic energy stored in the coronal magnetic arcades via reconnection, and several large scale numereical simulation models have been developed to model CMEs and EPs in which reconnection is accomplished by speci fied and/or numerical dissipations.  They have not yet produced quantitative agreement with the observed CME acceleration and propagation to 1 AU. In this talk, I will present a new concept that yields model CME EP dynamics in good quantitative agreement with data. The basic driving force is the toroidal Lorentz hoop force acting on a flux rope with two legs anchored in the Sun. The prominence mass is The initial flux rope is driven out of equilibrium by increasing its poloidal flux. The calculated acceleration and subsequent propagation of model CMEs have been shown to correctly replicate the observed CME dynamics from the Sun to 1 AU. The increasing poloidal flux produces an electromotive force (EMF) that is sufficient to accelerate particles to X ray energies. The new model shows that the predicted temporal profile of the EMF for a CME is in close agree ment with the observed X ray light curve of the associated falre. Furthermore, it is demonstrated that the EFR model can be driven by the observed CME position data alone to correctly yield the CME magnetic field structure observed in situ at 1 AU.

Work supported by Naval Research Laboratory Base Program