Forecast of the arrival of interplanetary shocks by measuring cosmic ray fluctuations in the interplanetary medium

Abstract

Here we present a method to forecast the arrival of an interplanetary shock to the Earth's orbit in advance of up to one day, using cosmic ray fluctuations and solar wind parameters measured onboard the ACE spacecraft. The method is based on our previous results [1]. By means of continuous monitoring of the interplanetary space state since April 2010, we conclude that not all shocks can be reliably forecasted by the method. Only those interplanetary shocks, for which a large flux of low-energy particles (10 keV − 10 MeV) of solar or interplanetary origin exists in the upstream region, can be forecasted. This is typically related to quasi-parallel shocks. In the absence of such particles, a forecast cannot be made. This is a typical situation for quasi-perpendicular shocks. Our analysis shows that, on average, an interplanetary shock can be forecasted for several hours up to one day, with the probability about 70%.