MODEL FOR DEXTRAL AND SINISTRAL PROMINENCES

In a recent paper Martin and coworkers have discussed several striking facts about the structure of solar prominences and the filament chann els in which they lie. They form two classes, called dextral and sinis tral. In a dextral (sinistral) prominence, an observer viewing a promi nence or filament channel from the positive-polarity side would see th e magnetic field point to the right (left) along the axis of the filam ent channel, whereas an observer viewing from above would see the prom inence feet bear off the axis to the right (left). Furthermore, dextra l prominences dominate the northern hemisphere and sinistral the south ern hemisphere, regardless of the cycle. Fibrils in the filament chann els do not cross the prominence but usually stream from or to plagette s parallel to the prominence axis. These pioneering observations sugge st that there is a coherent organizational principle orchestrating the global nature of prominences, and they have led us to reexamine the s tandard paradigms of contemporary prominence theory, such as that (1) prominences form in a sheared force-free arcade, (2) formation is by r adiative instability, (3) the prominence material is static, and (4) e ruption occurs when the shear or twist is too great. We propose a new model which accounts for the above new observational features in a nat ural way, replaces many of the above paradigms, and explains the previ ously puzzling feet of a prominence. It is a dynamic model in which a prominence is maintained by the continual input of mass and magnetic f lux. The correct global dextral and sinistral patterns for high-latitu de east-west prominences (such as those in the polar crown) are create d by an organizational principle that includes the combined effects of differential rotation on subphotospheric flux, its subsequent emergen ce by magnetic buoyancy, and its rearrangement by flux reconnection to form a filament channel with magnetic flux oriented along its axis. C ontinual emergence and reconnection creates a prominence as a flux tub e along the filament channel axis and filled with cool plasma which is lifted up from the photosphere and chromosphere by the reconnection p rocess. Prominences at low latitudes are in this model formed in a sim ilar way, except that it is a general subphotospheric flow (rather tha n differential rotation) which acts and so may produce either dextral or sinistral structures, depending on the sense of the flow. The effec t of neighboring plagettes in avoiding the prominence and making it sn ake its way along the filament channel is modeled. It is suggested tha t feet are short-lived structures caused by the interaction of nearby magnetic fragments with the prominence field and may represent either the addition or the extraction of mass from the prominence.