The HESPERIA REleASE notification system

The HESPERIA Relativistic Electron Alert System for Exploration (HESPERIA REleASE) makes use of relativistic electrons (v > 0.9 c) provided by the Electron Proton Helium Instrument (EPHIN) on SOHO and near-relativistic (v <0.8 c) electron measurements from the Electron Proton Alpha Monitor (EPAM) aboard the Advanced Composition Explorer (ACE), providing deterministic forecasts of the expected proton flux at two energy ranges: 15.8-39.8 MeV and 28.2-50.1 MeV.

In order to illustrate in real-time and in a user-friendly mode the expected radiation impact, as this is forecasted by REleASE, three discrete levels were chosen. In particular:

─    Quiet l Green color
─    Warning l Orange color
─    Alert l Red Color

As a result, a gauge that incorporates all three stages in real-time mode has been implemented. The needle indicates the expected radiation impact, according to the above labeling. 


Historic (not real-time) data of SOHO/EPHIN and ACE/EPAM from 2009 to 2016 were used to find a good forecast condition for SEP event and to quantify the event-oriented validation metrics (POD, FAR and warning time). We tested different combination of forecasts for different time offsets and found that the following condition delivered the best performance of the forecast systems:

  • Alarm: if any forecast >10-1 (cm2 sec sr MeV)-1 and one 30 minute forecast >10-2 (cm2 sec sr MeV)-1.
  • Event: if real proton flux >10-1 (cm2 sec sr MeV)-1.

Table 1. Results of REleASE implementation utilizing either SOHO/EPHIN or ACE/EPAM.

  True Missed False POD % FAR % Average warning time / min
EPHIN 24 14 10 63 29 107
EPAM 24 14 13 63 35 123

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