On the Support of Loop Prominences

The principal feature of the recently published 2002 model of Ashbourn and Woods concerned with the support of a quiescent prominence comprised of a number of closely coupled adjacent magnetoplasma loops was a balance between the upward force due to an electric current I flowing around a typical loop of the prominence and the downward force of gravity, g. If the gradient of the circuit inductance in a direction x is L super('), then the force in that direction is [image] L super(')I super(2), and hence for equilibrium in the vertical direction of a section of the loop of mass M, the equation [image] L super(')I super(2) = Mg must be satisfied. However, in this model lateral stability was not discussed, and there appears to be no force restraining the plasma loop from expanding sideways under the inductance gradient force. In this paper it is shown that lateral stability requires the currents flowing around the loop to be confined to helical threads, the structure of which results in a tension force capable of opposing the gradient force. The problem of stopping the plasma within the loop from flowing along the loop down to the photosphere will be considered in another paper.