THE MODULATION OF GALACTIC COSMIC-RAY ELECTRONS IN THE HELIOSHEATH

Journal Article · Fri Dec 10 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/725/1/121· OSTI ID:21474441

Caballero-Lopez, R A ^[1]; Moraal, H ^[2]

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1. Instituto de Geofisica, UNAM, 04510 Mexico, D. F. (Mexico)
2. Unit for Space Physics, School of Physical and Chemical Sciences, North-West University, Potchefstroom 2520 (South Africa)

Voyager 1 has observed strong increases in the intensities of 2-160 MeV electrons since crossing the termination shock of the heliosphere in 2004 December. Before this time these intensities were submerged below the detector background, except for occasional transient events. These increases are large compared to the concurrent increases of positive ions such as H, He, and O. A significant part is probably due to temporal effects as the heliosphere was recovering to solar minimum conditions from 2005 to early 2010. The intensity observed by Voyager 2 since its crossing of the shock in 2007 September is 5-10 times lower than that observed by Voyager 1, which is so low that the electron intensity may still be below the background produced by high-energy protons in the detector. This points to a large north-south asymmetry in the properties of the heliosheath. It is shown that the observations suggest that these electrons are not freshly accelerated on the termination shock, but rather that they are of galactic origin-while they may be re-accelerated by that shock. In this paper, these intensities are modeled with numerical solutions of the cosmic-ray transport equation. It is shown that because they are relativistic, the electrons are much more sensitive to the form of the diffusion coefficient at low rigidities than ions, and that this can explain the asymmetry.

• OSTI ID: 21474441
• Journal Information: Astrophysical Journal, Vol. 725, Issue 1; Other Information: DOI: 10.1088/0004-637X/725/1/121; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
CATIONS
COSMIC RADIATION
ELECTRONS
HELIOSPHERE
MAGNETIC FIELDS
NORTH-SOUTH ASYMMETRY
NUMERICAL SOLUTION
PROTONS
RELATIVISTIC RANGE
SUN
TRANSPORT THEORY
TURBULENCE
VOYAGER SPACE PROBES
ASYMMETRY
ATMOSPHERES
BARYONS
CHARGED PARTICLES
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRONS
IONIZING RADIATIONS
IONS
LEPTONS
MAIN SEQUENCE STARS
MATHEMATICAL SOLUTIONS
NUCLEONS
RADIATIONS
SOLAR ATMOSPHERE
SPACE VEHICLES
STARS
STELLAR ATMOSPHERES
VEHICLES