Work

Voyager 1 Observations of Galactic Cosmic Ray Isotopes in the Very Local Interstellar Medium: Evidence for Primary 2H and B

Year: 2025

Type: conference-paper

Abstract: We present the first measurements of the energy spectra of the isotopes of Galactic cosmic rays (GCRs) with nuclear charge $Z$=1--14 in the very local interstellar medium (VLISM). The observations are from the Cosmic Ray Subsystem (CRS) on the Voyager~1 (V1) spacecraft and cover the $Z$-dependent energy range from $\sim$3-661 MeV/nucleon. The data are fit to eight models using the GCR propagation code \galprop{}, and provide a new set of GCR elemental source abundances. The models all have injection spectra as power laws in rigidity, all with the same power-law index, and fit exclusively to the V1 data. The eight models differ in the relative abundances and by having two options for production cross sections and four options for total fragmentation cross sections. The VLISM energy spectra generated by all eight models agree reasonably well with the observed VLISM energy spectra for the isotopes with $Z$ from 1--14. However, in all models it was necessary to add contributions from a primary source of $^2$H and B.

Source: International Cosmic Ray Conference

DOI: 10.22323/1.501.0098

Authors: Igor V Moskalenko, Alan C. Cummings, Bryant C. Heikkila, Gudlaugur Johannesson, Troy A. Porter

Institutions: Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, California Institute of Technology, Goddard Space Flight Center, University of Iceland

Language: English

Topic: Astrophysics and Cosmic Phenomena

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Funders: National Aeronautics and Space Administration, Nuclear Safety and Security Commission

Awards: G2164914035, G6542238805, G8242476543