Acceleration of energetic protons by interplanetary shocks

Abstract

The University of Iowa instrument aboard Pioneer 11 detected 69 energetic proton events (EPE) (0.6 ≤ E p ≤3.4 MeV) during 1973–1974 in the heliocentric radial range 1–5 AU. Sixty percent of the EPE peak within ±5 hours of a corotating interaction region (CIR) boundary, while 19% peak inside and 21% peak outside the interaction regions. Of the CIR boundaries at which an EPE peaks within ±5 hours, 80% have associated shocks. The observed intensities and pitch angle distributions of protons near shock fronts are consistent with a theoretical simulation of the acceleration of protons by a ▽| B | drift in a V × B electric field at the shock front.