Quasi-linear theory and the phenomenology of interplanetary solar particle transport

Abstract

There is an apparent discrepancy between the scattering mean free paths as derived (1) empirically from solar particle events, and (2) theoretically within the framework of quasi-linear theory from measured magnetic field fluctuation spectra. A quasi-linear theory is applied to Helios data in a form that includes spectral steepening, cross and magnetic helicity, and non-Alfvenic dispersion relations in the resonance condition at high frequencies. Inserting the observed steepening of the power spectra at high wavenumbers leads to significant changes in the predicted mean free paths. Proton scattering mean free paths for three selected solar flare events, using plasma turbulence conditions, are calculated. It is shown, since the three solar flare events display different degrees of scattering, that the extended quasi-linear theory in the wave and slab model context, with implemented local scattering conditions, can correctly describe the dynamics of solar particle events in the interplanetary medium.