1. Prominences

(a) Dextral-Sinistral Model

Sara Martin has made an important discovery about the global nature of prominences, namely that most of them are dextral in the northern hemisphere (with right-ward branching barbs when viewed from above and a right-directed axial magnetic field when viewed from the positive polarity side) and sinistral in the southern hemisphere (with a corresponding left-orientated character). We have therefore developed with invaluable suggestions from Sara Martin and other members of the PROM team a model (Priest, van Ballegooijen and MacKay, 1996, Astrophys. J. 460, 530) to explain these properties.

(b) Model for Global and Fibril Structure

More recently, we have developed the above ideas further to give a Dynamic Dextral-Sinistral model for the structure and evolution of prominences (Priest, 1997, Proc IAU Colloq 167, ed. D Webb et al, in press) suggesting the following:

1. On a fine scale, prominences consist of many fine threads with two kinds of origin - some are lifted up from the upper photosphere in response to flux cancellation in small tubes - some continually form from the corona and heat up again in response to a localised heating mechanism.
2. On a large scale, the overall structure is of a large-scale horizontal flux tube along the polarity inversion line, with an overlying arcade linking the network. The structure of the filament channel and of barbs is explained by the distribution of flux sources along the channels, with majority polarity producing plagettes and minority polarity the barbs.
3. The chirality of polar-crown prominences may be produced by a combination of subsurface flows, flux-emergence and reconnection. Most low-latitude prominences have a chirality that are a natural consequence of nonuniform flux distribution and converging flux.

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