Clarify how Qin & Shalchi (2014) constructed PADCs under strong turbulence

Establish how Qin and Shalchi (2014) constructed a constant pitch-angle diffusion coefficient from full-orbit simulations in regimes of strong turbulence where the mean-squared-displacement-based running coefficient loses its constant plateau and exhibits 1/t decay, and assess the validity of that approach for reproducible numerical studies.

Background

The paper reviews prior simulation studies that compute pitch-angle diffusion coefficients (PADCs) from test-particle transport in synthetic turbulence, noting that several methods produce running coefficients with initial oscillations followed by 1/t decay as turbulence strength increases. Qin & Shalchi (2009) reported difficulty finding constant PADCs at high turbulence levels, and Riordan & Pe’er (2019) described the disappearance of constant plateaus with increased turbulence.

Against this backdrop, the authors note that it is unclear how Qin & Shalchi (2014) addressed the stronger turbulence regime in their simulations, motivating clarification of the methodology used to obtain stable PADC estimates under such conditions.