Comment on - 'Upstream energetic ions under radial IMF - A critical test of the Fermi model'

A criticism is offered by Fusilier of the conclusion by Sarris and Krimigis (SK, 1988) that the failure to observe energetic ions continuously under near radial interplanetary magnetic field conditions contradicts a fundamental prediction of the Fermi mechanism for the origin of the upstream ions. It is argued that both events reported by SK fall short of critical tests of the Fermi mechanism because the magnetic turbulence required by the Fermi process is not guaranteed to be present. Sarris replies that the ad hoc limit on the local angle between the magnetic field and the shock normal imposed by Fusilier is not a relevant consideration to upstream ion activity.