The Drift Coefficient for Energetic Particles in a Turbulent Plasma

Abstract Although the drift effect is well known to play an important role in the transport process of energetic charged particles in the heliosphere, the widely adopted standard drift coefficient only reflects the uniformity of the large-scale magnetic field. The drift arising from the turbulent electromagnetic field was investigated by Stawicki with quasilinear theory. However, some higher-order terms in the Fokker–Planck coefficient were ignored in his model in order to simplify a laborious calculation. We revisit Stawicki’s model by incorporating higher-order terms and discuss extensively the properties of the general form of the drift coefficient. We propose a new parametric form of the suppression factor ( f s ), defined as the ratio of the net and standard drift coefficients, which is very distinct from some previous models. According to the calculated f s , we find that suppression occurs at a similar level during the solar minimum (2008/1–2010/12) and solar maximum (2013/1–2015/12).