Comparison of theoretical expectations and observationally inferred values of the Poynting flux from sub-Alfvénic interaction in Proxima, for an open Parker spiral magnetic field geometry, as a function of the radial distance to the Proxima Cen star. Upper panel: Alfvén number, M_A. The curves in the lower panel correspond to the theoretical Poynting flux, , for two different models of the interaction: the Saur/Turnpenney model (Saur et al. 2013; Turnpenney et al. 2018; solid blue line) and the Zarka-Lanza model (Zarka 2007; Lanza 2009; solid green line). The orange shaded region corresponds to the range of observationally inferred Poynting fluxes, , allowed by our observed radio flux densities, and the dashed line is drawn at the orbital distance of Proxima b.