STK SEET Galactic Cosmic Rays (GCR)

The STK SEET Galactic Cosmic Rays (GCR) capability provides three different model options: CREME86, ISO-15390, and Badhwar-O’Neill 2010. The primary differences among these models are the amount of data on which the model is based and the way they model solar modulation. All three models calculate particle fluxes in free space outside the Earth’s magnetosphere (untrapped radiation). No geomagnetic cutoff effects are currently applied. Therefore, the models only apply to geosynchronous orbit or beyond; application to lower orbits will result in an upper limit to the GCR fluxes. SEET outputs for GCRs currently consist only of reports and graphs with no 2D or 3D graphics.

For additional background information, consult: SEET: Space Environment and Effects Tool for STK (PDF).

Options for STK SEET Environment - Galactic Cosmic Rays

Option Description
Model Options are:
  • BO10 - Badhwar-O'Neill 2010 model, based on measurements of GCR flux from solar cycles 19 to 24 (1955 - 2010) mainly from the NASA Advanced Composition Explorer (ACE) Cosmic Ray Isotope Spectrometer (CRIS), measuring the low-energy (50-300 MeV/n) spectrum for all ions from lithium (3) to nickel (28). Solar modulation is determined using functions similar to those in ISO-15390.
  • CREME86 - The Cosmic Ray Effects on Microelectronics model (Adams, 1987). Energy spectra are based primarily on measurements of hydrogen and helium in the energy range 10 MeV/n to 100 GeV/n. For most other elements, fluxes are scaled from the helium spectrum using either a constant or energy-dependent factor. Solar-cycle modulation is modeled as a sinusoidal variation with solar minimum in February 1975 and solar maximum in August 1980. Because the sinusoidal variation does not represent the true solar-cycle modulation, CREME86 should only be used for the solar extrema.
  • ISO15390 - An internationally adopted standard for computing GCR spectra based on measurements until about the year 2000 (Nymmik, 2000). Multi-parameter fits relate the solar modulation to observed sunspot numbers, accounting for the time lag between solar activity and the GCR flux at Earth, which varies between about 8 and 15 months depending on the phase and polarity of the solar magnetic field and on the magnetic rigidity of the particles.
Atomic Number

Elements from 1 (Hydrogen) to 92 (Uranium)
Solar Influence

This option is available with BO10 or CREME86.

  • "Solar Max" - Corresponds to either Φ = 1100 (BO10) or influence at 1908/08/05T10:04:04.8 UT (CREME86)
  • "Solar Min" - Corresponds to either Φ = 450 (BO10) or influence at 1975/02/21T14:18:14.4 UT (CREME86)
Interplanetary Weather Index

CREME86 model only. Specifies the contribution of singly- or fully-ionized anomalous cosmic rays (ACRs):

  • M=1 - Normal background environment providing the best approximation to the galactic cosmic ray flux at the given date (default).
  • M=2 - The fully-ionized "anomalous" component, added to galactic cosmic rays.
  • M=3 - "90%" worst-case galactic cosmic ray fluxes that allow uncertainties in flux data and solar activity, i.e., fluxes that are so severe that they have only a 10% chance of being exceeded by actual fluxes at any moment.
  • M=4 - Singly-ionized anomalous component. The singly-ionized particles are affected differently than fully-ionized particles by geomagnetic cutoff.
PHI (Φ) Displays the value of Φ used to compute the solar modulation for the BO10 model. (This value cannot be edited and is displayed for informational purposes only.)
Sample Time Frequency interval of the GCR computation, defining the cadence of the flux spectral output. Input unit is fractional years. If the sample interval exceeds the scenario time range, only one spectrum is returned.

Adams, J. H., Jr, (1987), Cosmic Ray Effects on Microelectronics, Part IV. NRL Memo Rep. 5901, Naval Research Laboratory, Washington, DC.

Badhwar, G. D., and P. M. O'Neill (2010), "Badhwar-O'Neill 2010 Galactic Cosmic Ray Flux Model--Revised." IEEE Trans. Nucl. Sci., Vol. 57, No. 6, pp. 3148-3153.

Nymmik, R.A. (2000) “Time lag of galactic cosmic ray modulation: Conformity to general regularities and influence on particle energy spectra,” Adv. Space Res., v. 26, no. 11, pp. 1875–2000.