Solar Quiet Environment

The solar-quiet ("no flare") model in CREME represents the ambient environment which prevails in the absence of solar energetic particle ("flare") events. This environment, which varies slowly in intensity over the 22-year solar cycle, is the basic environment in which all space systems must operate. When you choose this model, you must specify the part of the solar cycle you wish to consider:

• Solar Minimum (Cosmic Ray Maximum, last observed in 1986-87)
• Solar Maximum (Cosmic Ray Minimum, last observed in 1989-91, expected again in 2000-2002.)
• A specific year date (eg. 1996.80)

The solar-quiet environment includes:

• Galactic cosmic rays: Galactic cosmic rays dominate the spectra above ~50 MeV/nuc and extend to very high energies. They cannot be eliminated by either material or geomagnetic shielding and therefore must always be taken into account in the design of space systems.
  • The galactic cosmic ray environment currently available in CREME is based on "A Model of Galactic Cosmic Ray Fluxes", by R.A. Nymmik, M.I. Panasyuk, T. I. Pervaja, and A.A. Suslov, Nucl. Tracks & Radiat. Meas, 20, 427-429 (1992). This model has solar minimum flux levels generally comparable to that found in the old CREME (1986) model but provides a substantially better description of the solar cycle variation.
• Anomalous cosmic rays: These ions dominate the spectra of certain elements at ~10-50 MeV/nuc at solar minimum. Their spectra extend to higher energies with relatively soft spectra. However, unlike galactic cosmic rays, anomalous cosmic rays are not fully stripped of electrons. As a result, they can penetrate Earth's magnetic field with relative ease and can thus be an important source of high-LET ions in some low-inclination orbits.
  • The anomalous cosmic ray model in CREME is based on the latest composition, spectra, and charge state measurements from SAMPEX, as well as the historical record of anomalous cosmic ray measurements extending back to 1972.
• Low-energy component: Additional fluxes, which arise from various acceleration processes at the Sun and in interplanetary space, dominate the spectra of most elements below ~10 MeV/nuc.
  • This low-energy component is highly variable and is therefore represented in the solar-quiet model only at "typical" levels. Fortunately, its low energies make it irrelevant to most space engineering applications.

For more information on solar-quiet environments in CREME, see:

• A.J. Tylka et al. "CREME96: A Revision of the Cosmic Ray Effects on Micro-Electronics Code", IEEE Transactions on Nuclear Science 44