6.A2 The solar component consists of a fairly constant flux of electrons, protons and a few ions, flowing radially out, known as the solar wind, and of anomalous, only partially periodic events called solar particle events. The latter are correlated with solar flares. VI.A.2.1: The Solar Wind: The solar wind is a neutral plasma of total density of about 10 particles per cubic centimeter with a mean radial velocity of 425 km/sec at one AU from the sun. Figures 6.Al and 6.A2 and Table 6.Al illustrate typical solar wind parameters. VI.A.2.2: Solar Particle Events: Solar particle events consist mostly of protons of 10-100 MeV and are correlated with solar flares. They have a sharp flux rise for several hours, after which they decay exponentially with time periods on the order of several days. As a rule they are anisotropic with respect to the Sun. Solar particle events are generally described in terms of probabilities for accumulating a given dose over a given period of time, given certain particle parameters, such as ability to pass through a given mass shielding column density. There seem to be two claspes of events, labeled OR or ordinary and AL or anomalously large. Each of these event classes is treated separately statistically. A typical probability chart of intensity for solar particle events is shown on Figure 6.A3. VI.A.2.3: The Galactic Background Radiation: The galactic cosmic ray background consists of a variety of particles with energies up to at least 10 20 eV. The particles are mostly protons, with significant fluxes of electrons, heavy nuclei to at least Fe, positrons and y-rays. Of significance is that the cosmic ray flux is relatively low compared to the solar wind and particle events. The cosmic ray background is isotropic to better than .1%, and for purposes here will be considered isotropic. Even though it is not exactly known how the cosmic rays are accelerated to their very high energies, there is a vast amount of data on cosmic rays and their effects. Reference (6.Al) gives what is probably the best available empirical fit at this time to the galactic cosmic ray background over the entire range of energies.
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