Motion of solar cosmic rays in the coronal magnetic field

Abstract

Trajectories of solar cosmic rays have been calculated in a static ninth-order coronal magnetic field. It is found that as a result of field curvature and gradients, protons drift across the field lines at a rate of up to 200 y/32 deg hr -a. These drift rates are of the same order as, but somewhat smaller than, empirically derived rates. Localized enhancements of magnetic field have been inserted into the ninth-order field in order to model (in a highly idealized manner) the effects of the small-scale magnetic features which give rise to X-ray bright points. The motions of the particles in the presence of these scattering centers can be parameterized approximately by a cross-field diffusion coefficient. Our estimates of this coefficient, although crude, overlap with empirical values which have been deduced over a wide range of energies.We propose that coronal propagation of solar cosmic rays has two components. One is independent of particle velocity, and is associated with dynamic field phenomena (such as an expanding magnetic bottle): this is the only component which is important in flares which occur close to the foot-point of the Sun-Earth field line. The second component is velocity dependent, but is independent of mass, and is associated with scattering off (relatively static) magnetic inhomogeneities with scale sizes of at least 500 km: the second component contributes to coronal propagation if the flare occurs more than about 50-60 deg away from the Sun-Earth field line.

Solar Cosmic Rays

“…One of them is a coherent (convective) transport which is presumably realized either by flare shock or by expanding magnetic structure (bottle) associated with closed magnetic loops above the flare. Below we consider this issue in some detail relying upon the model of magnetic bottle developed by Schatten and Mullan (1977), Mullan and Schatten (1979), and Mullan (1983).…”

“…It should be noted that the drift effects have been calculated by Mullan and Schatten (1979) to simulate particle motion outside the boundary of the magnetic bottle, in the static corona, using a 9th order harmonic expansion of the coronal field. Their results are therefore applicable only to particle transport in the quiet corona -due to perpendicular diffusion and drift, with gradual escape of particles to interplanetary space.…”

“…A magnetic bottle was chosen by Perez-Peraza et al (1992), as the basis for the interpretation of two-peak SPEs, since this model seems to be well substantiated physically and elaborated numerically (Schatten and Mullan 1977;Mullan and Schatten 1979;Mullan 1983). Besides, as noted by Mullan and Schatten (1979), this model does not contradict the CME concept.…”

A New Model for Solar‐Terrestrial Propagation of Solar Cosmic Rays

“…As the slower propagation process is performed at a rate of 24 [10] and the particles in the LPR are from the FPR, the …”

“…16 cm 2 /s in two step processes according to Perez-Peraza [10] . As the slower propagation process is performed at a rate of 24 [10] and the particles in the LPR are from the FPR, the …”