UPDATE OF THE ESP MODEL FOR SOLAR PROTON RISK ASSESSMENT* M.A. Xapsos 1, C. Stauffer 2, G.B. Gee 2, J.L. Barth 1, E.G. Stassinopoulos 1 and R.E. McGuire 1 1 NASA Goddard Space Flight Center, Greenbelt, MD SGT Inc., Greenbelt, MD *Supported by the NASA SEE Program

OUTLINE Background on Solar Particle Models for Cumulative Fluence Results  Construction of an Integrated Data Set of solar proton data from IMP and GOES series of satellites  Inclusion of solar minimum time period  Extension of statistical model to higher energies Summary

SOLAR PROTON MODELS King and Stassinopoulos IMPSolar Max10 – 100 MeV JPLIMP and OGOSolar Max1 – 60 MeV ESPIMP and GOESSolar Max1 – 100 MeV (extrap. to 300) Model:Data*:Time Period:Energy Range: * Data from different instruments evaluated independently

CONSTRUCTION OF AN INTEGRATED DATA SET (IDS) The measurements made by IMP and GOES instruments are to a large extent complementary  IMP-8 GME Instrument  Data has outstanding energy resolution (30 energy bins ranging from 0.88 to 485 MeV)  Low detector noise levels  Detectors saturate at high fluxes  GOES Instruments  Provide 10 energy bins ranging from 0.6 to 700 MeV  Relatively high noise levels, especially at high energy  Performs very well at high flux rates Integrating these features together produces a better overall data base.

Integrated Data – October 19, 1989 Event

Fluence-Energy Spectra October 19, 1989 Event

SOLAR CYCLE DEPENDENCE Solar activity levels vary substantially for solar max  use statistical model, e.g. King, JPL, ESP Solar min activity level is low and reasonably constant  model as low “background” activity, always present

Model Solar Minimum Flux Levels

Models for Solar Maximum

Model Solar Cycle Dependence Confidence = 90%

SUMMARY An integrated data set of IMP and GOES solar proton data has been developed  Used to extend the model energy range out to 327 MeV  Used to model the solar minimum time period, thus giving a complete solar cycle description Generally during solar minimum:  Event frequencies are smaller  Event magnitudes are smaller  Energy spectra are softer Also nearly finished:  Model for 1 to 100 MeV/nucleon alpha particles based on IMP and GOES data  Model for elements C thru Fe (~10 to ~100 MeV/nucleon) based on ACE data