On shock strength and electric fields in the inner heliosphere

I explore the scaling of shock strength, cross-shock and convection electric field with heliospheric radius in the inner heliosphere. In the low β _e inner heliosphere, the primary contribution to the cross-shock field may be due to Hall currents, which are shown to scale non-monotonically with Mach number and exhibit a local minimum near the Alfvèn speed peak at several solar radii. This allows that the shock and cross-shock component of the convection fields are nearly equal |ěc{E}_shock| ≈ (ěc{v} × ěc{B})_x, which is a condition for high efficiency of the shock-surfing mechanism of ion acceleration. Shock-surfing is thought to be a injection mechanism to diffusive acceleration and, indeed, observations show that energetic ion events are often accelerated at near this same heliospheric radius.