ﻻ يوجد ملخص باللغة العربية
We study diffusion of charged particles in stationary stochastic magnetic field ${bf B}$ with zero mean, $langle {bf B} rangle = 0 $. In the case when electric current is carried by electrons, the field is force-free, $mathrm{curl} ,{bf B} = alpha{bf B} $, where $alpha({bf r})$ is an arbitrary scalar function. In a small region where the function $alpha $ and the field magnitude $|{bf B}|$ are approximately constant, the equations of motion of charged particles are integrated and reduced to the equation of mathematical pendulum. The transition from trapped to untrapped particles is continuously traced. Averaging over the magnetic field spectrum gives the spatial diffusion coefficient $D$ of particles as a function of the Larmor radius $r_L$ in the large-scale magnetic fields ($B_{LS}$) and magnetic field correlation length $L_0$. The diffusion coefficient turns out to be proportional to the Larmor radius, $Dpropto r_L $, for $r_L <L_0 / 2pi $, and to the Larmor radius squared, $ D propto r_L^2 $, for $ r_L> L_0 /2pi $. We apply obtained results to the diffusion of cosmic rays in the Galaxy, which contains a large number of independent regions with parameters $L_0$ and $B_{LS}$ varying in wide range. We average over $B_{LS}$ with the Kolmogorov spectrum and over $L_0$ with the distribution function $f(L_0)propto L_0^{- 1+ sigma}$. For the practically flat spectrum $sigma = 1/15$, we have $ Dpropto r_m^{0.7}$, which is consistent with observations.
The radial spread of charged particles emitted from a point source in a magnetic field is a potential source of systematic error for any experiment where magnetic fields guide charged particles to detectors with finite size. Assuming uniform probabil
3D picture of the coronal magnetic field remains an outstanding problem in solar physics, particularly, in active regions. Nonlinear force-free field reconstructions that employ routinely available full-disk photospheric vector magnetograms represent
Extrapolations of solar photospheric vector magnetograms into three-dimensional magnetic fields in the chromosphere and corona are usually done under the assumption that the fields are force-free. The field calculations can be improved by preprocessi
Force-free extrapolations are widely used to study the magnetic field in the solar corona based on surface measurements. The extrapolations assume that the ratio of internal energy of the plasma to magnetic energy, the plasma-beta is negligible. Desp
A formalism for describing charged particles interaction in both a finite volume and a uniform magnetic field is presented. In the case of short-range interaction between charged particles, we show that the factorization between short-range physics a