Lower limit to the altitude of coronal particle storage regions deduced from solar proton energy spectra

The spectrum of low energy protons observed at 1 AU following solar flares shows little or no evidence of energy degradation down to approximately 0.3 MeV. Such observations may be used to set a lower limit on the altidue of hypothetical coronal particle storage regions, ranging from 2 to 7 R, (Krimigis and Verzanu, 1971; Verzanu and Krimigis, 1972). It is pointed out that closed coronal magnetic loop structures are observed to extend to less than 2 R, so that long term (greater than 1 day) storage of low energy protons does not take place in the immediate vicinity of the sun. It is further suggested that in the few cases where the proton spectrum appears to be degraded at low energies, the energy loss may be due to adiabatic deceleration in the expanding solar wind (Parker, 1965). The alternative of continual accleration is suggested as a plausible substitute for the particle storage hypothesis. (U.S.)