Solar proton event patterns: the rising portion of five solar cycles Original Research Article

Using solar proton data from the past four solar cycles we have found that while there is no consistent pattern in the distribution of solar proton events throughout each cycle, there is a surprising consistency in the total number of events over each cycle. In comparing the distribution of solar proton events during the rising portion of cycles 19–23, we find a similarity between the 20th and the 23rd solar cycles. During solar cycle 20, only 17% of the proton events for the entire cycle had occurred during the first three years of the cycle and 28% had occurred during the first four years. If cycles 20 and 23 are similar, we would expect the majority of solar proton events to occur during years 5–8 of the 23rd cycle (i.e. from 2001–2004).