EARLY-TIME VELOCITY AUTOCORRELATION FOR CHARGED PARTICLES DIFFUSION AND DRIFT IN STATIC MAGNETIC TURBULENCE

Journal Article · Mon Aug 20 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/755/2/114· OSTI ID:22039094

Fraschetti, F; Giacalone, J ^[1]

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1. Department of Planetary Sciences and Astronomy, University of Arizona, Tucson, AZ 85721 (United States)

Using test-particle simulations, we investigate the temporal dependence of the two-point velocity correlation function for charged particles scattering in a time-independent spatially fluctuating magnetic field derived from a three-dimensional isotropic turbulence power spectrum. Such a correlation function allowed us to compute the spatial coefficients of diffusion both parallel and perpendicular to the average magnetic field. Our simulations confirm the dependence of the perpendicular diffusion coefficient on turbulence energy density and particle energy predicted previously by a model for early-time charged particle transport. Using the computed diffusion coefficients, we exploit the particle velocity autocorrelation to investigate the timescale over which the particles 'decorrelate' from the solution to the unperturbed equation of motion. Decorrelation timescales are evaluated for parallel and perpendicular motions, including the drift of the particles from the local magnetic field line. The regimes of strong and weak magnetic turbulence are compared for various values of the ratio of the particle gyroradius to the correlation length of the magnetic turbulence. Our simulation parameters can be applied to energetic particles in the interplanetary space, cosmic rays at the supernova shocks, and cosmic-rays transport in the intergalactic medium.

• OSTI ID: 22039094
• Journal Information: Astrophysical Journal, Vol. 755, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTRONOMY
ASTROPHYSICS
CHARGED PARTICLES
CHARGED-PARTICLE TRANSPORT
COMPUTERIZED SIMULATION
CORRELATION FUNCTIONS
CORRELATIONS
COSMIC RADIATION
DIFFUSION
ENERGY DENSITY
EQUATIONS OF MOTION
INTERPLANETARY SPACE
MAGNETIC FIELDS
MATHEMATICAL SOLUTIONS
TEST PARTICLES
THREE-DIMENSIONAL CALCULATIONS
TURBULENCE