Precise and Accurate Short-term Forecasting of Solar Energetic Particle Events with Multivariate Time Series Classifiers

Abstract

Solar energetic particle (SEP) events are one of the most crucial aspects of space weather that require continuous monitoring and forecasting using robust methods. We demonstrate a proof of concept of using a data-driven supervised classification framework on a multivariate time series data set covering solar cycles 22, 23, and 24. We implement ensemble modeling that merges the results from three proton channels (E$\geq$10 MeV, 50 MeV, and 100 MeV) and the long band X-ray flux (1-8{\AA}) channel from the Geostationary Operational Environmental Satellite missions. Our task is binary classification, such that the aim of the model is to distinguish strong SEP events from nonevents. Here, strong SEP events are those crossing the Space Weather Prediction Center's "S1" threshold of solar radiation storm and proton fluxes below that are weak SEP events. In addition, we consider periods of non-occurrence of SEPs following a flare with magnitudes $\geq$C6.0 to maintain a natural imbalance of sample distribution. In our data set, there are 244 strong SEP events comprising the positive class. There are 189 weak events and 2,460 "SEP-quiet" periods for the negative class. We experiment with summary statistic classifier, one-nearest neighbor and supervised time series forest (STSF), and compare their performances to validate our methods for prediction windows from 5 min up to 60 min. We find STSF to perform better under all circumstances. For an optimal classification threshold of $\approx$0.3 and a 60 min prediction window, we obtain: TSS = 0.850, HSS = 0.878, GSS = 0.783.