STEREO REleASE+: Adding Robustness to Solar Proton Event Forecasting in the Heliosphere by Means of Automated Recognition of Type‐III Radio Bursts

We report on the real‐time implementation of a local solar proton event forecasting system at the Solar Terrestrial Relations Observatory-Ahead (STEREO-A) spacecraft, namely STEREO REleASE+. The forecasting uses the finding that relativistic electrons provide the “earliest indication” that a solar particle event has started. They arrive at near‐Earth distance earlier than protons at ∼30% of the speed of light. In addition to relativistic electrons, we use a requirement of a radio burst of type III to be observed before issuing a proton alert. A similar system, HESPERIA REleASE+, has already been implemented using electrons observed by SOHO and ACE near Earth, which creates local forecasts for the Earth‐moon system. The radio observations from STEREO‐A are used in both systems, given that radio bursts in parts of their emission spectrum can be observed from all around the Sun. Usefulness of adding a radio burst requirement to an electron‐based forecasting system lies in the potential for suppression of known sources of false alarms, adding robustness. While this work describes the establishment of the real‐time system, we have also started investigating the two local and robust forecasts to test how far away from the spacecraft the validity and usefulness of the local forecasts extend (Droege et al., submitted Abstract EGU26-8207, this conference). Moreover, the STEREO REleASE+ system, currently located between Earth and Earth‐Sun L4, adds an additional safeguard for exploration of the moon, in particular from solar particle events originating behind the western limb of the Sun.