Isotopic and elemental composition of the anomalous low-energy cosmic-ray fluxes

Recent observations of cosmic rays below ~30 MeV nucleon^(-1) have revealed anomalous enhancements in the energy spectra of oxygen, nitrogen, and helium relative to those of other nuclei such as boron and carbon. We have measured the quiet-time fluxes of the elements hydrogen through oxygen in the ~4-30 MeV nucleon^(-1) energy interval during the period 1972 October through 1974 October. We find that the low-energy fluxes of Li, Be, B, and Care consistent with those expected from adiabatic deceleration and show no significant evidence for secondary fragmentation products arising from the enhanced nitrogen and oxygen fluxes. In the ~6-12 MeV nucleon^(-1) interval, the observed nitrogen and oxygen nuclei are predominantly ^(14)N and ^(16)O, with upper limits (84% confidence level) of ^(15)N/N ≤ 0.26, ^(17)O/O ≤ 0.13, and ^(18)O/O ≤ 0.12 for the other stable nitrogen and oxygen isotopes. These isotopic measurements are consistent with the presumed isotopic composition of the neutral interstellar medium, as would be the case if the anomalous component is locally accelerated. If, on the other hand, the enhanced low-energy cosmic rays result from unusual nucleosynthesis processes which enhance nitrogen and oxygen but not carbon, then these processes are constrained to producing predominantly ^(14)N and ^(16)O

The Elemental Composition of 4-30 MeV/nuc Cosmic Ray Nuclei with 1 ≤ Z ≤ 8

Recent observations of low energy cosmic rays have shown enhanced fluxes of nitrogen and oxygen relative to other elements in the ~8-30 MeV/nuc energy interval. We have extended the measurements of lithium through oxygen down to ~ 4 MeV/nuc with the Caltech Electron/Isotope Spectrometers on IMP-7 and -8 during solar quiet periods from October 1972 to September 1974. We find no evidence for significant enhancements of Li, Be, B. or C, which are found to have energy spectra consistent with those expected from the adiabatic deceleration of higher energy galactic cosmic rays. The He, N, and O fluxes are greatly enhanced when compared to the other elements, with relative abundances of O/He ~ 0.25, O/B ~ 100, and O/C ~ 30 at ~ 5 to 12.5 MeV/nuc

Isotopic Composition of the Anomalous Low Energy Cosmic Ray Nitrogen and Oxygen

The isotopic composition of the enhanced fluxes of cosmic ray nitrogen and oxygen observed below 30 MeV/nuc is of interest, whether the nuclei are a sample from some nearby galactic source region that is underabundant in carbon, or a sample of the neutral interstellar medium. Enhanced fluxes in the 6 to 12 MeV/nuc energy interval were measured over a two year period with the Caltech Electron/Isotope Spectrometer on IMP-7. The observed low-energy nitrogen and oxygen nuclei are predominantly N-14 and O-16, with upper limits (84% confidence level) of N-15/N below 0.26, O-17/0 below 0.13, and O-18/0 below 0.12 for other isotopes in the 6-12 MeV/nuc energy interval. The implications of these results for the origin of the enhanced nitrogen and oxygen fluxes are discussed

Produtividade de forragem de genótipos de trevo-persa em terras baixas.

O objetivo deste trabalho foi avaliar a produtividade de materiais de trevo-persa desenvolvidos pelo programa de Melhoramento de Leguminosas Forrageiras de Clima Temperado da Embrapa