Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹

Abstract

We have made a new analysis of cosmic-ray data from the CRS experiment on the Voyager 2 (V2) spacecraft. This analysis, which includes both penetrating and stopping particles in the HET telescope, extends the energy range from an upper energy limit of 100-300 MeV nucleon À1 for stopping particles to over 1 GeV nucleon À1 . This analysis provides almost continuous spectra over this broad energy range, including the peak in the differential spectra of the various nuclei. This enables us to obtain the relationship between the shape of the low-energy interstellar differential spectrum and the amount of solar modulation. Measurements at V2 at the modulation minimum in 1987 and again in 1997-1998 give nearly the same intensities and therefore the same solar modulation parameter, ¼ 260 MV, which is much lower than the value of 400 MV at the Earth. most of the modulation was occurring beyond 54 AU and also that the interplanetary part of the solar modulation out to $54 AU in the two time periods of opposite solar magnetic polarity was greatly different. The measured secondary/ primary ratios B/C and N/O can be fitted equally well using a simple leaky-box Galactic propagation model with an escape length $ P À0:5 either with a break in the escape dependence at 1 GeV nucleon À1 or with no break in the escape-length dependence to the accuracy of the experimental data itself, AE3%, over the entire energy range from less than 100 MeV nucleon À1 to over 10 GeV nucleon À1 using a combination of both V2 data at the lower energies and HEAO data at the higher energies. This same escape-length dependence also predicts the measured higher Z secondary/primary ratio Z ¼ 21-23/Fe well at all energies.

Cosmic-Ray Propagation and Interactions in the Galaxy

“…It has been claimed that no break in X(R) is required to fit Voyager 2 outerheliosphere B/C, N/O and sub-Fe/Fe data extended to 1.5 GeV, plus HEAO3 data, and adopting suitable solar modulation levels (123). Voyager 2 provides a unique dataset because of the low solar modulation.…”

The Starburst Contribution to the Extragalactic γ‐Ray Background

“…In the Galaxy, the diffusive escape timescale for 10 GeV protons is inferred to be diA $ 3 ; 10 7 yr near the solar circle (Garcia-Munoz et al 1977;Connell 1998). Such protons interact with a mean total column density of $10 g cm À2 before escaping, and the column decreases at higher energies roughly as E À1 = 2 (e.g., Engelmann et al 1990;Webber et al 2003). These observations imply that 10 GeV cosmic rays interact with matter of density n $ 0:2 cm À3 , somewhat below the average density of the ISM in the gas disk of the Milky Way.…”

Astrophysical implications of a visible dark matter sector from a custodially warped GUT

“…The correction factor obeys g = 1 for L ≪ R , and becomes smaller than one if the distance of the solar system from the radial edge is taken comparable to the scale height of the cylinder. For the CR grammage we adopt the parametrization [108] (see also [98,109] for earlier estimates)…”