Solar Energetic Proton forecasting with REleASE during STEREO-A’s flyby of Earth

Solar Energetic Particle (SEP) events can pose a significant radiation hazard for human and robotic space exploration activities. Therefore SEP forecasting systems are needed to support operations. The REleASE system (A. Posner, 2007) utilizes the fact that near relativistic electrons (1 MeV electrons have 94% of the speed of light) travel faster than ions (30 MeV protons have 25% of the speed of light) and are always present in hazardous SEP events. Their early arrival can be used to forecast the expected proton flux. Originally REleASE uses real time data from SOHO/EPHIN near Earth. Since the instrument is aging we recently adapted the method to STEREO-A/HET and used the period from June to November 2023 when STEREO-A passed the Earth to compare the REleASE forecasts from the different instruments.This study has received funding from the National Aeronautics and Space Administration under grant agreement No. TXS0150642 (HESPERIA RELEASE).