ON THE MAGNETIC FIELDS SUPPORTING QUIESCENT SOLAR PROMINENCES

摘要

We present a theory for the magnetic fields supporting a quiescent prominence comprised of a number of adjacent magnetoplasma loops―the treatment is essentially three-dimensional. The principal feature is a balance between the upward force due to an electric current flowing around a typical loop of the prominence and the downward forces of gravity. A new treatment is that the electric current force is derived from the expression for the circuit energy, 1/2LI~2, where Ⅰ is the total electric current and L is the inductance. The equilibrium condition relates the angle α between the magnetic field and the axis of the prominence to the nondi-mensional height h/l, where l is the distance between the footpoints. We deduce from this condition that to support a typical prominence, we need a magnetic field greater than 6 G and a value for α of about 30°, not far from the observed mean value of 25°. We also show that prominences for which α exceeds 55° are unstable.