Variation in the Longitudinal Dependence of Solar Proton Intensities with Solar Cycles

Abstract: Based on a study of two-dimensional solar flare distributions according to the intensity of soft X‑ray burst peaks and solar proton peaks, it is concluded that the heliolongitudinal dependence of solar proton peak intensity varies with solar cycles. GOES spacecraft data on X-ray bursts in the wavelength range of 0.1–0.8 nm and data on solar proton events with proton energies above 30 MeV are used. It is found that the heliolongitudinal reduction in the peak intensity of proton events in different cycles can differ by an order of magnitude. The reduction in the peak intensities of proton events after flares in the heliolongitudinal interval of 0–30 E relative to the peak intensities of proton events from flares on the western hemisphere of the Sun’s disk is 30 for solar cycle 23 and only 3 for solar cycle 22. The variation in the longitudinal dependence of solar proton peak intensities with solar cycles must be considered in all statistical studies of proton events. © 2019, Allerton Press, Inc.