engleski

Numerical diffusion-expansion Forbush decrease model, ForbMod

An analytical diffusion-expansion Forbush decrease (FD) model, ForbMod, first presented in Dumbović et al. (2018) provides a method to calculate FD amplitude from the parameters of the flux rope (FR) part of the ICME. In this model, FR has a cylindrical shape and it is initially free of cosmic ray (CR) particles. FR moves with a constant velocity and expands in an interplanetary space while the magnetic field inside it decreases. It's radius is a function of time and it expands self-similarly slowly filling with CR particles by perpendicular diffusion. We first modified the original ForbMod to include particles of all energies. Then we used it to obtain the values of power-law indices for the radius and magnetic field changes from the observed FD amplitudes in the center of the FR. Since power-law indices need to be calculated numerically, we test the numerical method and examine the range of values of FR parameters which would result in power-law indices being in the expected range. We apply the model to several events and analyse the results.

Sun, Heliosphere, coronal mass ejection, forbush decreases, galactic cosmic rays

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