Abstract:
We have studied the evolution of two dark H-alpha filaments as prominences during their disk passage from February 12 to February 19, 1992 and from March 6 to March 17, 1992, using Kodaikanal Observatory H-alpha and Ca II K spectroheliograms. Both the filaments were well outside the spot regions. However, they were connected to sunspots by small threads. Outside the spot regions, the filaments were also anchored between opposite polarity plage regions. Both the filaments were almost straight in the beginning. However, they acquired a curved shape (inverted U-shape) as the spot and plages underwent rotation. It is shown that rotation of the plage and spot plays an important role in the evolution of prominences, one serving as the anchor and the other imparting necessary shear. Once the shear reaches a critical value, it starts unwinding the filaments, resulting in the fine structure of the two prominences studied.
