Abstract
Realistic modeling of complex physical phenomena is always quite a challenging task. The main problem usually concerns the uncertainties surrounding model input parameters, especially when not all information about a modeled phenomenon is known. In such cases, Approximate Bayesian Computation (ABC) methodology may be helpful. The ABC is based on a comparison of the model output data with the experimental data, to estimate the best set of input parameters of the particular model. In this paper, we present a framework applying the ABC methodology to estimate the parameters of the model of Forbush decrease (Fd) of the galactic cosmic ray intensity. The Fd is modeled by the numerical solution of the Fokker–Planck equation in five-dimensional space (three spatial variables, the time and particles energy). The most problematic in Fd modeling is the lack of detailed knowledge about the spatial and temporal profiles of the parameters responsible for the creation of the Fd. Among these parameters, the diffusion coefficient plays a central role. We employ the ABC Sequential Monte Carlo algorithm, scanning the space of the diffusion coefficient parameters within the region of the heliosphere where the Fd is created. Assessment of the correctness of the proposed parameters is done by comparing the model output data with the experimental data of the galactic cosmic ray intensity. The particular attention is put on the rigidity dependence of the rigidity spectrum exponent. The proposed framework is adopted to create the model of the Fd observed by the neutron monitors and ground muon telescope in November 2004.
Highlights
The galactic cosmic rays (GCR) are the charged particles traveling from the outer interplanetary space into the heliosphere
The rigidity dependence of the exponent γ( R) defines the parameter ζ. We present how these values are estimated by the Approximate Bayesian Computation (ABC) method so that the amplitudes of the Forbush decrease (Fd) stochastic model matched the observational amplitudes of Fd registered in November 2004 by the neutron monitors and muon telescopes
We have selected the data from four neutron monitors and two channels of Nagoya muon telescope
Summary
The galactic cosmic rays (GCR) are the charged particles traveling from the outer interplanetary space into the heliosphere. During their travel through the interplanetary medium, GCRs are undergoing the influence (modulation) of the solar wind and the combination of the regular and turbulent interplanetary magnetic field (IMF) being the sources of various kind of drifts and diffusion of the GCR particles. The most known are the 22-years, 11-years and 27-days variations connected with the recurrent changes in the Sun activity. We observe the short time (a few days) sporadic changes connected directly with the Sun activity and solar wind.
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