(a) Normalized B_θ time–distance plot. The magnetic field initially exhibits a series of small twists that correspond to the Alfvén wave. These gradually amplify and form a standing shock, as is the case with v_θ. The twist is continual in the same direction and the time taken for the twists to travel from the shock to the photopshere and back to the shock decreases upon each reflection. Panel (b) shows that amplification and direction of the magnetic twist more clearly at z = 0.3. Panel (c) highlights that the twist is not confined to the region between the shock and photosphere as a large amount of twisting occurs before the shock passes through z = 0.99. Once the shock propagates beyond the low-chromosphere, the magnetic flux tube remains permanently twisted.

(An animation of this figure is available.)

The video/animation of this figure is available in the online journal.