coronal transients

coronal transients

(coronal mass ejections) Huge eruptions of gas from the solar corona into the interplanetary medium, first observed from space in the early 1970s. They seem to occur at a rate of about one per day (around the time of sunspot maximum – see sunspot cycle) and are in many cases associated with the sudden rapid ascent of a quiescent filament (see disparation brusque) or, to a lesser extent, with an energetic flare.

Typically, a coronal transient expels around 1012–1013 kg of coronal material, often in the form of a ‘bubble’ with a clearly defined leading edge. This expands as it is accelerated outward to a final speed of 200–1000 km s–1 after about an hour. The passage of a transient through the corona ‘straightens' the coronal magnetic field lines, making them more nearly radial, and thereby allows magnetic flux emerging from the photosphere to occupy a greater volume.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006