Solar energetic particles (SEPs) are high-energy particles, such as protons, which are accelerated at the Sun and speed outward into the solar system. If they reach Earth, they can be harmful to satellites, ionospheric communications, and humans in space or on polar airline routes. NOAA defines an SEP event as an occasion when the flux of protons with energies higher than 10 MeV exceeds 10 pfu (particle flux units) as measured by the GOES satellites in geosynchronous orbit. The most intense SEP events are associated with shocks, driven by coronal mass ejections (CMEs), which accelerate particles as they move through the corona. However, very few CMEs result in SEP events. In this talk, we present both the development of two operationally useful SEP tools (a nowcast for low Earth orbit and a forecast to predict future events) and research towards improving forecasts through the study of Type II and Type III solar radio bursts.
To assess the risk from SEPs in Low Earth orbit in real-time, we created a web-based nowcast of SEP flux. The tool determines the current solar energetic proton flux level given input position (latitude, longitude, and altitude) and energy of the protons (e.g., > 10 MeV). The effective cutoff energy is calculated for the location and current geomagnetic storm level (i.e., the Kp value from SWPC) using the Shea & Smart (e.g., Smart et al. 1999abc, 2000) geomagnetic cutoff model. Additionally, to predict future events, we developed a web-based SEP forecast tool based on the occurrence of X-ray flares and Type III radio bursts.
Finally, the research results we present are part of summer work funded through the University of Colorado’s LASP REU program in Space Physics. We examined data from the WAVES instrument on the WIND satellite, to characterize the properties of Type II/III radio bursts and local Langmuir waves. A principal component analysis was used to determine which of these factors are most relevant to the occurrence of SEP events. In total, we present the analysis of all type II radio bursts observed by WIND between January 2010 and May 2013.
Lisa Winter (AER), Rick Quinn (AER), and Kathryn Ledbetter (Wellesley College)