Quiet-time properties of low-energy (less than 10 MeV per nucleon) interplanetary ions during solar maximum and solar minimum

Abstract

We have examined the abundances and spectra of ∼1-10 MeV per nucleon protons, 3He, 4He, C, O Fe during solar quiet periods from 1978 to 1987 in an effort to investigate the recent suggestion by Wenzel et al. that the ions may be of solar origin. We find that the intensities of the ions, other than O, fall by an order of magnitude between solar maximum and solar minimum, and that the > 1 MeV per nucleon ions exhibit weak streaming away from the Sun. More significantly, the quiet-time ions during solar maximum have 3He-rich and Fe-rich abundances which are established characteristics of small impulsive solar flares. Thus, we suggest that small unresolved impulsive flares make a substantial contribution to the "quiet-time" fluxes. 4He from these flares may also contribute strongly to the ion spectra that were reported for the 35-1600 keV energy range by Wenzel et al. © 1990. The American Astronomical Society. All rights reserved.