Modulation of anomalous protons with increasing solar activity Original Research Article

A comprehensive time-dependent drift-modulation model including a solar wind termination shock (TS) is used to study the acceleration and modulation of anomalous protons in the outer heliosphere with increasing solar activity. The development of solar modulation from minimum to maximum is represented by increasing the ‘tilt angle α’ from 10° to 70°, reducing global drifts, changing the effectiveness of the TS directly by decreasing the compression ratio s, and by decreasing the effective radial diffusion coefficient. These changes are studied for both polarity epochs. Surprisingly, the effectiveness of the acceleration of the ACR protons improves with increasing α for the A > 0 polarty cycle but not for A < 0. With α = 70° a switch in HIVIF polarity from A > 0 to A < 0 causes only a slight increase in the intensity between 80 AU and 90 AU. Changing s has a profound effect on all spectra.