Solar Particle Events and Self-Organized Criticality: Are Deterministic Predictions of Events Possible?

Evidence is presented that solar particle events are a self-organized critical phenomenon. Using daily and monthly fluences of solar protons measured by the IMP-8 and GOES satellite instrumentation over a 28-year period, long-term correlation of events, fractal characteristics and power function behavior for the density functions of fluence magnitudes and waiting times are demonstrated. The implications are that it is not possible to predict the time of occurrence and magnitude of solar particle events within narrow limits.