Geomagnetic Weather Conditions

Disturbances in current systems in Earth's magnetosphere can change the magnetic fields in near-Earth space. In general, these disturbances reduce the magnetic shielding and increase the cosmic ray fluxes in Earth orbits.

Two magnetic weather levels are presently available in the CREME GTRN routine, a "quiet" magnetosphere (in which all fields are at nominal levels) and a very "stormy" magnetosphere (in which cosmic-ray access to Earth orbits is significantly increased).

For calculations intended to reflect long-term averages, the quiet condition should be selected. However, for "worst case" and "peak rate" calculations, the "stormy" condition should be considered.

In particular, large magnetospheric storms often accompany solar energetic particle ("SEP") events. The "stormy" option should always be used in conjunction with the "worst-day" and "peak-flux" SEP options in the FLUX routine.

Note that when making a GTRN calculation for an arbitrary orbit (ie., using the orbital parameters input instead of one of the pre-calculated orbits), the magnetic weather condition is approximated using the techniques from the original CREME model. The weather conditions for arbitrary orbits do not correspond exactly to those used in the pre-calculated orbits.