Dependence of Forbush-decrease characteristics on parameters of solar eruptions
 

I.M. Chertok (1), A.A. Abunin (1), A.V. Belov (1), V.V. Grechnev (2)

(1) Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Troitsk, Russia
(2)  Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia

Abstract. We analyze relations between characteristics of an extended ensemble of Forbush decreases (FDs) caused by CMEs from the central zone of the solar disk during the 23^rd solar cycle, on the one hand, and such solar eruption parameter as a summarized unsigned magnetic flux of CME-associated EUV dimmings and arcades, on the other hand. This eruption parameter is shown to have a pronounced direct correlation with the FD magnitude and a conspicuous reverse correlation with the ICME transit time from the Sun to the Earth. The revealed correlations indicate that main quantitative characteristics of major non-recurrent FDs (and geomagnetic storms as well) are largely determined by parameters of solar eruptions, in particular such as the summarized magnetic flux of dimmings and arcades.

An example of FD and geomagnetic storm (Kp and Dst indexes)

 

Figure: Dimmings and arcades in sources of the strongest FDs of the 23rd cycle  

 

Table: parameters of FDs and their solar eruptive sources  

 

Figure 1: FD magnetude vs. Eruptive magnetic flux  

Figure 2: FD onset and peak transit times vs. Eruptive magnetic flux  

 PDF file  of the 4-page paper prepared to the 23rd European Cosmic Ray Symposium  and 32nd Russian Cosmic Ray Conference, Lomonosov Moscow state university, Moscow, Russia,  July, 2 – 6, 2012