Title: The Different Shapes of the LIS Energy Spectra of Cosmic Ray He and C Nuclei Below ~1 GeV/nuc and The Cosmic Ray He/C Nuclei Ratio vs. Energy -V1 Measurements and LBM Propagation Predictions,
Abstract: This paper examines the cosmic ray He and C nuclei spectra below ~1 GeV/nuc,
as well as the very rapid increase in the He/C ratio below ~100 MeV/nuc,
measured by Voyager 1 beyond the heliopause. Using a simple Leaky Box Model
(LBM) for galactic propagation we have not been able to simultaneously
reproduce the individual He and C nuclei spectra and the large increase in He/C
ratio that is observed at low energies. However, using a truncated LBM with
different truncation parameters for each nucleus that are related to their rate
of energy loss by ionization which is ~Z2/A, these different features can be
matched. This suggests that we are observing the effects of the source
distribution of cosmic rays in the galaxy on the low energy spectra of cosmic
ray nuclei and that there may be a paucity of nearby sources. In this
propagation model we start very specific source spectra for He and C which are
~dj/dP = P-2.24, the same for each nucleus and also for all rigidities. These
source spectra become spectra with spectral indices ~-2.69 at high rigidities
for both charges as a result of a rigidity dependence of the diffusion
coefficient governing the propagation which is taken to be ~P-0.45. This
exponent is determined directly from the B/C ratio measured by AMS-2. These
propagated P-2.69 spectra, when extended to high energies, predict He and C
intensities and a He/C ratio that are within +3-5% of the intensities and ratio
recently measured by AMS-2 in the energy range from 10 to 1000 GeV/nuc.