Increases in the area of coronal holes related to interplanetary shocks

Abstract

The tracking of interplanetary disturbances by means of the interplanetary scintillation (IPS) of stellar radio sources showed that major interplanetary disturbances are originated from solar regions containing coronal holes. Thus interplanetary shocks may originate in changing coronal holes which suddenly emit faster solar wind. In this paper we present two examples of related solar and interplanetary observations corresponding to sudden commencement (SC) events at the Earth which show by different means that interplanetary shocks are, at least in some cases, related to an increase in the area of coronal holes. The events correspond to 6 June 1979 and 1 October 1991. A possible scenario at the Sun for the occurrence of an increase in the area of coronal holes and a mechanism for the formation of the shock are also presented.