EFFECT OF FINITE LARMOR RADIUS ON COSMIC-RAY PENETRATION INTO AN INTERPLANETARY MAGNETIC FLUX ROPE

Journal Article · Wed Sep 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/720/1/853· OSTI ID:21460088

Kubo, Yuki ^[1]; Shimazu, Hironori ^[2]

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1. Space Environment Group, National Institute of Information and Communications Technology, Tokyo 184-8795 (Japan)
2. Department of Information System Fundamentals, University of Electro-Communications, Tokyo 182-8585 (Japan)

We discuss a mechanism for cosmic-ray penetration into an interplanetary magnetic flux rope, particularly the effect of the finite Larmor radius and magnetic field irregularities. First, we derive analytical solutions for cosmic-ray behavior inside a magnetic flux rope, on the basis of the Newton-Lorentz equation of a particle, to investigate how cosmic rays penetrate magnetic flux ropes under an assumption of there being no scattering by small-scale magnetic field irregularities. The results show that the behavior of a particle is determined by only one parameter f{sub 0}, that is, the ratio of the Larmor radius at the flux rope axis to the flux rope radius. The analytical solutions show that cosmic rays cannot penetrate into the inner region of a flux rope by only gyration and gradient-curvature drift in the case of small f{sub 0}. Next, we perform a numerical simulation of a cosmic-ray penetration into an interplanetary magnetic flux rope by adding small-scale magnetic field irregularities. The results show that cosmic rays can penetrate into a magnetic flux rope even in the case of small f{sub 0} because of the effect of small-scale magnetic field irregularities. This simulation also shows that a cosmic-ray density distribution is greatly different from that deduced from a guiding center approximation because of the effect of the finite Larmor radius and magnetic field irregularities for the case of a moderate to large Larmor radius compared to the flux rope radius.

• OSTI ID: 21460088
• Journal Information: Astrophysical Journal, Vol. 720, Issue 1; Other Information: DOI: 10.1088/0004-637X/720/1/853; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANALYTICAL SOLUTION
COMPUTERIZED SIMULATION
COSMIC RADIATION
EQUATIONS
GUIDING-CENTER APPROXIMATION
INTERPLANETARY SPACE
LARMOR RADIUS
MAGNETIC FIELDS
MAGNETIC FLUX
MASS
SOLAR CORONA
SUN
APPROXIMATIONS
ATMOSPHERES
CALCULATION METHODS
IONIZING RADIATIONS
MAIN SEQUENCE STARS
MATHEMATICAL SOLUTIONS
RADIATIONS
SIMULATION
SOLAR ATMOSPHERE
SPACE
STARS
STELLAR ATMOSPHERES
STELLAR CORONAE