A major impact on human and robotic space exploration activities is the sudden and prompt occurrence of solar energetic ion events. The fact that near relativistic electrons (1 MeV electrons have 95% of the speed of light) travel faster than ions (30 MeV protons have 25% of the speed of light) and are always present in Solar Energetic Particle (SEP) events can be used to forecast the arrival of protons from SEP events with real-time measurements of near relativistic electrons. The faster electrons arrive at L1 30 to 90 minutes before the slower protons. The Relativistic Electron Alert System for Exploration (REleASE) forecasting scheme uses this effect to predict the proton flux by utilizing the actual electron flux and the increase of the electron flux in the last 60 minutes. A detailed description of the REleASE scheme can be found in Posner et al. (2007). The original REleASE code uses real-time electron flux measurements from the Electron Proton Helium Instrument (EPHIN) onboard the Solar Heliosperic Observatory (SOHO) to make forecasts of the the expected proton flux. This REleASE version provides SEP forecasting since 2008. The results can be found at http://costep2.nascom.nasa.gov
In the framework of the HESPERIA project, a clone of the REleASE system was built in the open source programming language PYTHON. The same forecasting principle with use of the same forecasting matrices were in addition adapted to real-time electron flux measurements from the Electron, Proton & Alpha Monitor (EPAM) onboard the Advanced Composition Explorer (ACE). It is shown, that the REleASE forecasting scheme can be adapted to work with any near relativistic electron flux measurements. The two resulting forecasts, one based on SOHO/EPHIN and one based on ACE/EPAM electron data, are shown below.
Posner, A., Up to 1-hour forecasting of radiation hazards from solar energetic ion events with relativistic electrons, Space Weather, Vol. 5, S05001, doi:10.1029/2006SW000268, 2007.
Description of plot:
The upper panel on both sides shows real-time proton fluxes measured by SOHO/EPHIN. The proton flux in the energy range of 15.8 to 39.8 MeV is shown in red and the proton flux in the energy range of 28.2 to 50.1 MeV is shown in green. The next three panels show the proton flux forecasts obtained with the RELEASE forecasting scheme. From top to bottom the panels show expected proton fluxes in 30, 60 and 90 minutes. On the left and right side the forecasts are based on electron measurements by SOHO/EPHIN and ACE/EPAM, respectively. All forecasts use the same color code as the real-time proton flux in the top panel. The bottom panels on both sides show the measured real-time electron fluxes used for the forecasts. The SOHO/EPHIN and ACE/EPAM electron fluxes cover the energy range of 0.25 to 1.0 MeV and 0.175 to 0.315 MeV, respectively.
Historic Data :
Historic data for REleASE can be found from Data Retrieval Tool.