Introduction to STEREO REleASE+:

STEREO REleASE+ combines the existing STEREO REleASE system (the relativistic electron module) with a novel radio module that qualifies type-III radio bursts as a precondition for a proton alert with the aim of reducing specific sources of false alarms. Type-III radio bursts, that are produced by electron beams accelerated in solar eruptive events travelling outward through the corona along open magnetic flux tubes, are used as an independent early evidence of particle escape from the Sun. The radio module automatically detects type-III radio bursts from STEREO-A SWAVES real-time radio spectrograms and determines a set of parameters that narrow down detected type-III radio bursts to those that have the potential of causing significant solar proton events at STEREO’s current location. STEREO REleASE+ issues a proton alert only if the relativistic electron module creates an alert within the forecasting window set by the radio module. STEREO REleASE+ switches back to STEREO REleASE when data gaps in real-time radio data prevent proper identification of relevant type-III bursts.

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.

Posner A. et al., 2025. STEREO REleASE+: Improving Solar Proton Event Forecasting by means of Automated Recognition of Type-III Radio Bursts, Space Weather Journal, in preparation.

Description of plot:

Both upper row panels show real-time proton fluxes measured by STEREO/HET in the energy range of 21.0 to 40.0 MeV. The next three panels show the proton flux forecasts in 30, 60 and 90 minutes (from top to bottom) obtained with the STEREO REleASE forecasting scheme, based on electron measurements by STEREO/HET (left column panels) and STEREO/SEPT (right column panels), respectively. In all forecast panels, vertical dashed blue lines - when present - indicate either the time that a proton alert is first issued by the forecasting system or the time of an updated (12-hour) proton alert within an already ongoing proton event. The fifth-row panels show the respective measured real-time electron fluxes used for the forecasts. The STEREO/HET and STEREO/SEPT electron fluxes cover the energy range of 0.7 to 4.0 MeV and 0.125 to 0.255 MeV, respectively. Both bottom panels show the real time STEREO/A SWAVES beacon radio fluxes (in dB) in the frequency range of 0.125 to 16 MHz, that are used for the identification of type-III radio bursts, indicative of particle escape from the Sun, with the potential of causing significant solar proton events (with fluxes surpassing the 0.22 cm^-2 s^-1 sr^-1 MeV^-1 threshold value). Red rectangles, when present, indicate the forecasting window (FW) set by the radio data, namely the maximum time interval within which a significant proton event is expected to occur after the onset of an associated strong type-III radio burst.

The thin bar just above the panel of STEREO/SEPT electron fluxes indicates whether contamination exists in STEREO/SEPT electron data (orange lines) or not (blue lines) based on the algorithm developed for STEREO REleASE that estimates the level of contamination in real time. When contamination exists (contamination level higher than 35%) no forecasts are produced from STEREO/SEPT data. Likewise, the thin bars above the bottom STEREO/A SWAVES panels show whether the proton flux forecasts above have been issued, at corresponding times, from the STEREO REleASE+ (orange lines) or the STEREO REleASE forecasting system (cyan lines).

In all proton flux panels, horizontal dashed lines indicate the 0.22 cm^-2 s^-1 sr^-1 MeV^-1 proton flux intensity threshold defining significant solar proton events (bottom dashed line), while the top dashed line is shown in order to guide the eye of the user about the peak intensity of the event and whether this crosses the threshold of 10 cm^-2 s^-1 sr^-1 MeV^-1. Furthermore, the vertical grey shaded areas within all panels indicate time periods during which the respective electron input data are available.

At the very bottom of the plots, we indicate if the STEREO REleASE+ forecasting system is presently running, or whether we have alternatively switched to STEREO REleASE due to the presence of significant gaps in STEREO/A SWAVES data.

Historic Data:

Historic data for STEREO REleASE+ can be found from Data Retrieval Tool (DRT).