As an interplay of plasma and magnetic field the solar prominences represent a nice example of cosmical hydromagnetics. Due to stronger magnetic fields in active regions the prominence processes are more violent there than in non-active regions. Observing with a coronagraph or watching prominence movies one recognizes some characteristic processes in prominences of active regions:
(a)Condensation of Hα material in coronal space without any direct observational evidence of the material supply. It seems that the material had been ejected in the form of corpuscular radiation, captured, thermalized and cooled down to 104 °K, when it becomes observable in the Hα line.(b)Dissolution of the Hα material. Knots, streamers of sprays, surges and puffs often undergo a reverse process: they dissolve and disappear when observed in Hα. Similar dissolution is typical for a great part of the material in eruptive prominences.(c)Spiraling motion and detwisting of streamers are observed in surges, sprays, funnels and also in eruptive prominences. In the prominence movies of HAO Boulder, Sacramento Peak Observatory and Pic-du-Midi we have found many nice examples. In most cases (if not in all) the detwisting resulted in a marked simplification of the prominence structure.(d)Emerging magnetic fields may be seen in form of small rising and expanding Hα loops (velocities about 50 km/sec). In this type of loops the material is dragged out of the chromosphere. A similar process with low velocities has been observed in 5303 Å movies of coronal condensations.(e)Capture of a surge by transversal magnetic fields has been observed and photographed on October 7, 1956. Surge material has been captured in a complex loopy structure and then streamed sunwards along the loops. This event shows that capturing of plasma streamers by transversal magnetic fields does occur on the Sun and that the material supply for AS prominences (see item (a)) would thus be possible.(f)Collisional processes occur in different forms. One has been just described in item (e). However, the well-known prominence of Lyot from 1937 shows that a surge hits a prominence without being (completely) captured. The prominence which has been hit decays and the surge material seems to be reflected (at least partly) downwards. Two colliding knots may bypass each other in complicated trajectories. Cases have been recorded of falling prominence knots being stopped and accelerated upwards, with measured acceleration more than 10 solar g.(g)Oscillating prominences at the limb have been photographed. The oscillations followed shortly after a nearby flare-spray event. This may be the counterpart of the disk phenomenon discovered by astronomers of Lockheed Observatory.
The spin-1/2 anisotropic Heisenberg-chain in longitudinal aaand transversal magnetic fields: a DMRG study