at various radii (from 2 to $10 R_{\star}$) with an isotropic velocity distribution. [Our assumption of a stationary magnetic field distribution implicitly ignores the effects on the disk of transients. Individual propagating shocks due to CMEs travelling across circumstellar space would disrupt the pre-existing large-scale magnetic field, resulting in changes in field topology and possibly in reconnection of field lines.]{}

The rate of energy change, $\Delta E$, for a nearly isotropic population of EPs in a flow with speed $V$ is determined to the lowest order in $V/c$ by the divergence of the flow speed and can be crudely estimated in the plasma frame by $$\Delta E/E = (2V/3r) \Delta t$$ during the elapsed time $\Delta t$ [@Kota:13]. In a stationary wind with speed $V \simeq 800$ km$/$s, an appreciable $\Delta E / E$ occurs only over a $\sim 1$ day time-scale. In our simulations, the vast majority of the EPs hit the disk or return to the stellar surface within 1–2 hours for $\sigma^2=0.1$. Over such a short time-scale as compared with the dynamical time-scale of the advected bulk of the star wind, the energy of the EPs does not change appreciably and the adiabatic approximation is justified. In 