Dynamical processes in the solar corona and interplanetary space (invited review)

Abstract

Observations of the solar corona collected over the past decade are discussed from the point of view of short-term (<1 day) and long-term (>1 year) effects. Various phenomena are described, including coronal mass ejections, shock waves, and magnetic sector structures. It is argued that emerging magnetic flux is probably the prime cause of these phenomena, although the details of the interaction processes in the corona are not fully understood.

Short-term changes are caused by the sudden release of energy in the lower corona or chromosphere. The prime cause is thought to be due to the build-up of highly sheared magnetic flux. Theoretical work of late has concentrated on attempting to explain the time-scales of flare events (<10 s) in terms of magnetic reconnection. Other work has concentrated on attempting to explain observed features of coronal mass ejections which last for periods of several hours. Long-term changes last for several years and are characterized by the slow evolution of coronal structures, especially magnetic sectors, which extend into interplanetary space out and beyond the Earth. Recent observations place new restraints on the solar dynamo which is thought to be responsible for the emerging magnetic flux involved in these long-term changes.