Evolution Reconstruction of Several Space Weather Events Connected with Forbush Decreases

I. Dorotovic¹, K. Kudela², M. Lorenc¹, M. Rybansk², T. Pinter¹

¹Slovak Central Observatory, 94701 Hurbanovo, Slovak Republic
²Institute of Experimental Physics SAS, Watsonova 47, 043 53 Kosice, Slovak Republic

In our recent paper (Dorotovic et al., Solar Physics, 2008, submitted) we focused on a study of Forbush decrease (FD) of January 17-18 and 21-22, 2005. Two typical FDs with different evolution of the recovery phase to the original level were analyzed and it has been shown that corresponding recovery time can depend on the density of high-energy protons in the CME matter, namely, that absorption of primary cosmic rays in the matter can be described as a possible cause of FD. The latter assumption, hovewer, has to be confirmed by adding more supporting events and this is the main aim of the present paper. We defined the ratio between the density of high-energy protons and low-energy ones as the main parameter to analyse the recovery phase of corresponding FDs. To verify the hypothesis, we identified several additional events and consequently the data on magnetic field and solar wind from GOES 10 and 12, and ACE satellites were used besides of basic input data from neutron monitors (NMs) at Lomnicka St-t, Oulu, South Pole, Haleakala, and Newark. Decreases of the level of neutron counts from NMs, proton flux density at ACE, P1 and P7 at GOES, as well as the IMF in the period of 1995-2007 were tested. Total of approximately 40 events have been analyzed to verify if their evolution can support the previous statements and the results are presented in a tabulat form. Individual events are commented whether a particular FD event can or cannot be connected with a flare at the Sun or a CME passage near the satellites.