Using Sunspot Number as an Indicator of Frequency of Solar Activity

Abstract:

Future solar activity has been predominately gauged by the phase of the solar cycle, with a higher activity level anticipated during solar maximum and a lower during solar minimum. The solar cycle is one of the few characteristics of the sun that can be predicted into the future. This allows models to create predictions of the level of solar activity during a mission when the mission is in its planning and development phases.

Over the past few decades, many models have been developed that can predict the monthly sunspot numbers for an entire solar cycle soon after the onset of the cycle. As these models have had time to mature, more scientists and agencies (e.g. NASA and NOAA) are using their predictions to describe the upcoming solar cycle.

We will present our findings on relating the frequency solar energetic particle (SEP) episodes to the smooth monthly sunspot number. First, we will show how the percentage of time that the energetic particle flux near Earth is elevated due to a SEP episode correlates with the smoothed monthly sunspot numbers. These percentage will be compared alongside similar percentages for both solar maximum and solar minimum. These comparisons will be done using multiple databases to remove the basis in episode identification.

Second, we will present a sunspot proxy model. This model uses the yearly sunspot number to predict the number of episodes that will occur during the year. Together with sunspot number predictions, this model provides the community with a way to accurately predict the number of SEP episodes that can be anticipated each year during the remainder of the solar cycle.

DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Approved for Public Release 20-MDA-10537 (27 Jul 20)