Anomalous diffusion of cosmic rays in magnetic field turbulence - Linkage between diffusion statistics and turbulence statistics

Fumiko Otsuka, Tohru Hada

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Anomalous diffusion of energetic charged particles (cosmic rays) is studied using a simple two-dimensional cross field diffusion model. Both super-diffusion and sub-diffusion can take place in the model. When typical Larmor radius of the particles is much less than the field correlation length, the particles essentially gradient-B drift along equi-contour lines of the magnetic field strength, and thus the diffusion in this parameter regime can essentially be understood by analyzing statistics of the magnetic field islands composed of these equi-contour lines. We numerically evaluate the statistics of the field islands such as the probability distribution function of island radius and fractal dimension of the island contour lines, as functions of the power-law index of the magnetic field turbulence. We find numerically and analytically the scaling laws of time-scale dependent diffusion coefficients using the parameters obtained by analysis of the field islands statistics.

    Original languageEnglish
    Pages (from-to)204-211
    Number of pages8
    JournalProgress of Theoretical Physics Supplement
    Volume162
    DOIs
    Publication statusPublished - Aug 18 2006

    Fingerprint

    linkages
    cosmic rays
    turbulence
    statistics
    magnetic fields
    Larmor radius
    probability distribution functions
    energetic particles
    scaling laws
    fractals
    field strength
    charged particles
    diffusion coefficient
    gradients
    radii

    All Science Journal Classification (ASJC) codes

    • Physics and Astronomy (miscellaneous)

    Cite this

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    abstract = "Anomalous diffusion of energetic charged particles (cosmic rays) is studied using a simple two-dimensional cross field diffusion model. Both super-diffusion and sub-diffusion can take place in the model. When typical Larmor radius of the particles is much less than the field correlation length, the particles essentially gradient-B drift along equi-contour lines of the magnetic field strength, and thus the diffusion in this parameter regime can essentially be understood by analyzing statistics of the magnetic field islands composed of these equi-contour lines. We numerically evaluate the statistics of the field islands such as the probability distribution function of island radius and fractal dimension of the island contour lines, as functions of the power-law index of the magnetic field turbulence. We find numerically and analytically the scaling laws of time-scale dependent diffusion coefficients using the parameters obtained by analysis of the field islands statistics.",
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    AU - Hada, Tohru

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    AB - Anomalous diffusion of energetic charged particles (cosmic rays) is studied using a simple two-dimensional cross field diffusion model. Both super-diffusion and sub-diffusion can take place in the model. When typical Larmor radius of the particles is much less than the field correlation length, the particles essentially gradient-B drift along equi-contour lines of the magnetic field strength, and thus the diffusion in this parameter regime can essentially be understood by analyzing statistics of the magnetic field islands composed of these equi-contour lines. We numerically evaluate the statistics of the field islands such as the probability distribution function of island radius and fractal dimension of the island contour lines, as functions of the power-law index of the magnetic field turbulence. We find numerically and analytically the scaling laws of time-scale dependent diffusion coefficients using the parameters obtained by analysis of the field islands statistics.

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