2018/10/19 by W. R. Webber, Webber, W. R., N. Lal +4
Earth and Planetary Sciences · Physics and Astronomy · #Astro and Planetary Science #Atmospheric Ozone and Climate #FOS: Physical sciences #Solar and Space Plasma Dynamics #Space Physics (physics.space-ph)
paper · pdf · doi:10.48550/arxiv.1810.08589
openalex publication_date 2018/10/19 · openalex created_date 2022/08/02 · openalex updated_date 2026/07/28
In this paper we report a study of the isotopic composition of Li, Be, B and\nN, Ne nuclei from a 5 year time period beyond the heliopause using the CRS\ninstruments on Voyager. By comparing the isotopic ratios, 15N/14N and 22Ne/20Ne\noutside the heliosphere as measured at Voyager, and which are found to be\nsignificantly lower than those measured at the same energy inside the\nheliosphere, we have provided strong evidence that cosmic rays of this energy\nhave lost as much as 200 MeV/nuc or more in the solar modulation process. This\nis in accordance with the so called force field description of this overall\nmodulation by Gleeson and Axford. The measurements at Voyager confirm that the\nunusual 14N and 22Ne cosmic ray source abundances relative to solar abundances\nmade earlier inside the heliosphere extend to the lower energies not accessible\nfrom near Earth measurements. The low energy Li, Be and B nuclei, which are\nbelieved to be purely secondary nuclei, are found to have a (previously\nunobservable) peak in the differential intensity spectrum at ~100 MeV/nuc. This\nis in agreement with propagation predictions. The intensities of these nuclei\nare ~10-20% higher than those predicted in a propagation model with a matter\npath length lambda = 9 g/cm2 at these low energies. The isotopic composition of\nLi, Be and B nuclei is also consistent with that expected from propagation\nthrough interstellar matter.\n