STEREO-REleASE

STEREO REleASE was developed following the same principles as the original REleASE system (see Posner et al. 2007). About 15 years of data from the STEREO-A High Energy Telescope (HET) and the Solar Electron Proton Telescope (SEPT) were used to create new and improved forecasting matrices for each instruments. As input the 0.125-0.255 MeV SEPT electron channel and the 0.7-4.0 MeV HET electron channel is utilized to predict the 21-40 MeV proton flux. These energy ranges are available in real time as STEREO-A beacon data. Since SEPT uses a Magnet/Foil-technique to measure electrons, proton contamination is possible and can lead to an increased number of false alarms. Therefore an algorithm was developed that can estimate the level of contamination in real time. With that the electron flux can be corrected as long as the contamination level stays below 35%. If the contamination exceeds this limit, the data are not used. A warning is issued as soon as two consecutive forecasts are above a threshold of 0.22 (s sr MeV cm2)-1. Warnings produced from the SEPT are always crosschecked with the forecasts of the ones from HET and require that these are at least above 0.11 (s sr MeV cm2)-1. A systematic validation on historic data resulted in a probability of detection of 87%, a false alarm rate of 25% and an average warning time of ~230 min with a median of ~54 min.

The model uses real-time electron flux measurements from STEREO-A/SEPT and STEREO-A/HET.

The STEREO REleASE model produces two forecasts: one based on inputs from STEREO-A/SEPT and one based on STEREO-A/HET electron data for the proton energy channel 21–40 MeV. Forecasts are produced with a lead time of 30, 60, and 90 minutes. Based on these forecasts, the STEREO REleASE Alert module generates an alert based on the combination of the three most recent forecasts derived from STEREO-A/SEPT and STEREO-A/HET data.

Version 1.0 was deployed on the CCMC CR system on February 4, 2026.

The following sentences and acknowledgements shall appear inline where the STEREO REleASE tool is presented and also when the STEREO REleASE tool is cited, mentioned as well as when the relevant results are presented, cited and mentioned:

"STEREO REleASE has been developed through funding from the National Aeronautics and Space Administration under grant agreement No. TXS0150641A (National Observatory of Athens) and No. TXS0150642 (Christian-Albrechts-Universität) and has been built in the open-source programming language PYTHON."

Moreover, the logo of the HESPERIA project as well as the logo of the National Aeronautics and Space Administration (NASA) will be displayed in due prominence in all these occasions in proper image file format to be provided by NOA.

Any commercial use of the STEREO REleASE SEP forecasting results by NASA/CCMC and/or migration of the STEREO REleASE model to an external system, i.e., other than NASA/CCMC, will be possible only after signature of a separate agreement between NASA/CCMC, the National Observatory of Athens and the Christian-Albrechts Universitaet zu Kiel, Germany.