2016/12/28 by W. R. Webber, Webber, W. R.
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Space Plasma Dynamics #Space Physics (physics.space-ph)
paper · pdf · doi:10.48550/arxiv.1612.08973
openalex publication_date 2016/12/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Voyager observations for over 3 years beyond the heliopause have started to define features of the low energy, less than 100 MeV per nuc, cosmic ray secondary nuclei that have a zero or negligibly small source component. As an example, the abundance of B between about 7 and 15 MeV per nuc is unexpectedly large, greater than the prediction of a LBM by 2 or 3 in the measurement and cross section error. On the other hand, for several other heavier secondary nuclei with a low source abundance such as F and Z equal 17 to 19 and 21 to 23 nuclei, in the corresponding energy channels between about 10-20 MeV/nuc, zero nuclei have been observed. The same LBM calculations would predict about 6 to 7 events for the sum of these three groups of nuclei. The B observed intensities could be more closely matched by considering a nested LBM with 0.3-1.0 g/cm2 of matter near the cosmic ray sources, essentially a source component of B. This nested LBM calculation, if extended to the production of the above groups of secondaries, would however predict a total 8 to 12 events thus leading to an even larger discrepancy with the zero events that are observed. The measurements of heavier secondaries at low energies therefore make it very problematical that a nested LBM with more than a few 0.1 g/cm2 or more of matter near the sources could be the source of the large B abundance seen by Voyager. The large abundance of B at the lowest energies is best understood, so far, as the result of production mostly from a matter traversal of 10 g/cm2 in the galaxy, possibly in combination with uncertainties in the data and cross sections at these low energies.