This version of the propagation code does not propagate protons, and it does not propagate Li and Be correctly. Therefore the data for these elements on this website should not be trusted.
The propagation code is capable of producing spectra for individual isotopes, but the user is only given access to element spectra on this website.
Solar modulation of the interstellar spectra is performed using the smod Fortran code developed by Mark Wiedenbeck. This code implements the spherically symmetric model of Fisk(1971), with a solar wind speed of 400 km/s, a diffusion coefficient kappa(R) = kappa_0 beta R, where R is the rigidity and beta the velocity of the cosmic ray, and a modulating volume extending to 120 AU. The strength of the modulation can then be described by a single parameter, Phi, as in Gleeson and Axford (1968).
The propagation/modulation model described above is used to fit ACE Oxygen spectra during the indicated time periods below. The climax neutron monitor averages for the same time periods are also obtained.
Start End Phi (MV) Climax 8/14/1997 3/18/1998 325 4274 12/13/1998 4/27/1999 430 4068 9/9/1998 1/22/2000 590 3881 1/22/2000 6/5/2000 765 3766 7/29/2000 2/3/2001 1050 3645 1/1/1990 1/1/1991 1300 3445 Note: derived from IMP8 He data
A smooth fit is calculated for Phi vs. Climax-data.
The modulation parameter for times in the past are calculated by looking up the Climax NM average for the appropriate time, and then calculating Phi from the fit to Phi vs. Climax-data.
The modulation parameter for times in the future are calculated by assuming that Climax data will repeat into the future with a 20.5-year period.
NOTE!!! The last update to this "prediction" method was in mid-2004. So, any "predictions" of the modulation parameter beyond ~2005 will be prettty bad, as we all know that the Sun has not behaved as expected since then...
NOTE: No attempt is made to account for well-known hysteresis effects that are observed when neutron-monitor data are plotted against Phi values derived from lower-energy satellite data. The Phi-Climax relationship is derived strictly from the table of Phi and Climax values listed above.