Formation and Development of Shock Waves In The Solar Corona and Interplanetary Space

At the Sun shock waves are produced either by flares or by coronal mass ejections and are regarded to be the source of solar energetic particle events. In the solar corona shock waves appear as type II radio bursts. The propagation of a disturbance away from an active region from the corona into the interplanetary space is considered by evaluating the radial behaviour of the Alfven speed. The magnetic field of an active region is modelled by a magnetic dipole superimposed on that of the quiet Sun. Such a magnetic field structure leads to a local minimum of the Alfvén speed in the middle of the corona and a maximum of 740 km/s at a distance of 3.8 solar radii from the center of the Sun. The occurrence of such a minimum and maximum has important consequences on the formation and development of shock waves in the corona and the interplanetary space and their ability to accelerate particles leading to a special temporal delay of the on-set of solar energetic particle events.