The influence of the energy emitted by solar flare soft X-ray bursts on the propagation of their associated interplanetary shock waves

Abstract

We have investigated the relationship between the thermal energy released from 29 solar flares and the propagation features of their associated interplanetary shock waves that were detected at 1 AU. The 29 interplanetary shock waves were identified unambiguously and their tracking from each solar flare was deduced by tracking their associated interplanetary type-II radio emission. The thermal energy released in the solar flares was estimated from the time-intensity profiles of 1–8 A soft X-ray bursts from each flare. We find a good relationship between the flares' thermal energy with the IP shock-waves' transient velocity and arrival time at the Earth — that is, the largest flare energy released is associated with the faster shock waves. The IP shock velocity (without influence of solar wind) varies asW+0.32 and transit time varies asW−0.32, wereW is the energy. The actual transit velocity at the IP shock (shock velocity + solar wind velocity) is exponentially proportional to the associated flare's thermal energy,Vactual≈W0.13. The flare thermal energy-shock velocity relationship could, we suggest, be used to predict the arrival time at the flare-generated IP shock at the Earth. Finally, we discuss a possible scenario of formation of a shock wave during the early phase of the flare and its propagation features.