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.