Temporal variations in fibril orientation

Abstract

We measure variations in orientation of fourteen dynamic fibrils as a function of time in a small isolated plage and nearby network using a 10- min time sequence of Hα filtergrams obtained by the Dutch Open Telescope. We found motions with average angular velocities of the order of 1 deg min−1 suggesting systematic turning from one limit position to another, particularly apparent in the case of fibrils with lifetimes of a few minutes. Shorter fibrils tend to turn faster than longer ones, which we interpret as due to vortex flows in the underlying granulation that twist magnetic fields.