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Probabilistic 3D Outer Zone Radiation Belt Model




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OBJECTIVE: The objective of this topic is to create an accurate predictive 3 dimensional radiation belt model which can support a capability that can provide an actionable forecast for "All Clear" or give the likelihood of an internal charging hazard. This will require forecasts of flux levels at a range of energies from as low as 500 keV to >2MeV electrons. The forecasts should be for up to 7 days, with probabilities and confidence levels. While the confidence levels at higher that 2 or 3 days out will likely be small given the current level of science, this will give us a base to work from for future improvements.


DESCRIPTION: The outer-zone radiation belts are a highly variable and dynamic population of very energetic electrons that exist between about 10,000 km and 40,000 km above the Earth’s surface at the equator, but penetrate to Low Earth Orbit at high latitudes. They can penetrate satellite surfaces and deposit their charge into or near the interior electronics, which can lead to damaging discharges. With the recent National Defense Strategy’s emphasis on resilient satellites, it is important to develop specification and forecast capabilities that can provide good estimates of the current and near future radiation belt threat levels to allow decision makers the best knowledge of the environment when planning upcoming operations. A knowledge of the environment also allows satellite operators the ability to quickly determine the probability of space environment contributions to anomalies, and more readily ascertain the possibility of pacing competitor "gray zone" activities that could lead to satellite malfunctions.


Current operational specification and forecast models such as the Spacecraft Environmental Anomalies Expert System – Real time (SEAESRT) and the Relativistic Electron Forecast Model used by the National Oceanic and Atmospheric Administration/Space Weather Prediction Center (NOAA/SWPC) only address geosynchronous orbit. Current science addresses the full outer-zone electron radiation belts, and should be able to significantly improve upon the existing capability. Some example 3D radiation belt models are the AFRL model [1], Dynamic Radiation Environment Assimilation Model (DREAM) [2], the British Antarctic Survey Radiation Belt Model [3] and others. For forecasting there are current efforts from simple approaches such as The Satellite Risk Prediction and Radiation Forecast System (SaRIF), to sophisticated efforts like SafeSpace model [5].


This is a call for new capabilities that can specify and forecast the energetic electron fluxes in the outer-zone for up to 7 days. These nowcasts and forecasts should include the probabilities of different flux levels at locations within the region and the confidence level of each probability. These fluxes will be used to drive a hazard specification capability.


PHASE I: Demonstrate a capability that can accurately specify hazardous radiation belt fluxes for energies in the range from 0.75 to 6 MeV and >2MeV using operational data.

  1. The fluxes must be specified throughout the outer radiation belt zone using accuracy and bias metrics which will be provided and for periods of time which will be specified.
  2. There will also be a demonstration that the capability can make accurate 24 and 48 hour forecasts of the same fluxes throughout the radiation belts with acceptable probabilities and confidence levels, using the provided metrics.


AFRL will specify the observations to be used for the truth data.


PHASE II: Phase II will have X objectives:

  1. Demonstrate that the performance in Phase I can be obtained with a real-time model that only uses operational data.
  2. The specification will be demonstrated for a more significant time period, as will the original forecast.
  3. The forecast with probabilities and confidence levels will be extended to 7 days, we will look for a reasonable fall-off in accuracy with time.
  4. The capability will be compared with a model being developed by a partner.


AFRL will specify the observations to be used for the truth data.

If the results are satisfactory, we will recommend this model to our customers, who will be following the effort, for a phase III transition.


PHASE III DUAL USE APPLICATIONS: The phased III will have as objectives:

  1. Further validation of the model to provide our customer with a more complete understanding of the model's strengths and weaknesses.
  2. Where time and resources permit, there may be further upgrades to the model based on the previous validation results.
  3. The main effort in phase III will be to produce an Algorithm Theoretical Basis Document and provide support to the team transitioning the capability to operations.



  1. Albert, J. M., N. P. Meredith, and R. B. Horne (2009), Three-dimensional diffusion simulation of outer radiation belt electrons during the 9 October 1990 magnetic storm, J. Geophys. Res., 114, A09214, doi:10.1029/2009JA014336.
  2. Reeves, G. D., Chen, Y., Cunningham, G. S., Friedel, R. W. H., Henderson, M. G., Jordanova, V. K., Koller, J., Morley, S. K., Thomsen, M. F., and Zaharia, S. (2012), Dynamic Radiation Environment Assimilation Model: DREAM, Space Weather, 10, S03006, doi:10.1029/2011SW000729.
  3. Glauert, S. A., Horne, R. B., and Meredith, N. P. (2014), Three-dimensional electron radiation belt simulations using the BAS Radiation Belt Model with new diffusion models for chorus, plasmaspheric hiss, and lightning-generated whistlers, J. Geophys. Res. Space Physics, 119, 268–289, doi:10.1002/2013JA019281.
  4. Horne, R. B., Glauert, S. A., Kirsch, P., Heynderickx, D., Bingham, S., Thorn, P., et al. (2021). The satellite risk prediction and radiation forecast system (SaRIF). Space Weather, 19, e2021SW002823.
  5. Brunet, A., Dahmen, N., Katsavrias, C., Santolík, O., Bernoux, G., Pierrard, V., et al. (2023). Improving the electron radiation belt nowcast and forecast using the SafeSpace data assimilation modeling pipeline. Space Weather, 21, e2022SW003377.
  6. Brunet, A., Dahmen, N., Katsavrias, C., Santolík, O., Bernoux, G., Pierrard, V., et al. (2023). Improving the electron radiation belt nowcast and forecast using the SafeSpace data assimilation modeling pipeline. Space Weather, 21, e2022SW003377.;


KEYWORDS: Radiation Belts; Outer-Zone; Forecast; Prediction

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