Voyager-1 Energy Spectra at Very Low Modulation Level
for Cosmic-Ray Nuclei - C, N, O, Ne, Mg, Si and Fe
and Deduced Local Interstellar Spectra.
A. Lukasiak, F.B. McDonald
Institute for Physical Science and Technology
University of Maryland, College Park, MD 20742, USA
W.R. Webber
Astronomy Department, New Mexico State University,
Las Cruces, NM 88003, USA
Data from the High Energy Telescope of the CRS experiment on Voyager-1 have been
used to measure absolute energy spectra of Galactic cosmic rays for C, N, O, Ne,
Mg, Si and Fe in the energy range from 20 - 350 MeV/n for carbon and up to
700 MeV/n for iron at two solar minimum periods 1986-1988 and 1997-1998 yrs. The
solar modulation deceleration parameter relevant for these data is estimated to
be around 380 MV and 315 MV. These very low modulation parameters are results of
the measurements being made in the outer heliosphere at heliocentric distances
of 30 and 69 AU, and centered on the solar minimum periods of cycles 21 and 22.
Local Interstellar Spectra are deduced using these Voyager-1 energy spectra,
propagation calculations and spherical-diffusion model. The Voyager-1 energy
spectra are compared with ACE energy spectra and the corresponding modulation
level of ACE measurement is discussed.