COMPUTATION OF THE MAGNETIC-FIELD AROUND A QUIESCENT PROMINENCE FROM OBSERVATIONAL DATA

A prominence is often modelized by a vertical infinitely thin massive current sheet Sigma embedded in the coronal half-space {z > 0}, and su pported against a uniform gravitational field -g (z) over cap by an x- invariant magnetic field which is potential outside Sigma. In the fram ework of this simple model, we reconsider the problem of the determina tion of the magnetic field from the knowledge of its normal components on both Sigma and the photospheric plane {z = 0}, the values of these quantities being assumed to be extracted from actual observational da ta. It is shown that there is in general no regular field satisfying t hese boundary conditions. A sensible ''regularization'' procedure can however be applied to the problem, which allows to determine a field i n a unique way. Conditions on the data for this field being actually a ble to support a prominence are established, and an explicit example i s computed.