A solar cycle statistical model for the projection of space radiation environment

The interplanetary plasma and radiation fields are affected by the degree of disturbance in the solar surface. Sunspot number is well correlated with many observable space quantities and is used herein to represent variations in the space radiation environment. A solar cycle statistical model is developed based on the accumulating cycle sunspot data in order to estimate future levels of cycle activity. In developing the model, the odd and even cycles are treated as two independent populations. Furthermore, the rising and declining phases of each cycle are treated separately due to the randomization through the remainder of the cycle. It is shown that all the historical sunspot cycles are reasonably consistent with each respective activity level, as the cycle progresses from its solar minimum/solar maximum. The ranges of mean percentile groups containing up-to-date cycle data are calculated in order to estimate future levels of cycle activity. The resultant projection of sunspot numbers will be used to estimate future space-related quantities of interest in radiation protection.