# Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence

## Abstract

The transport of energetic particles in a mean magnetic field and in the presence of anisotropic magnetic turbulence is studied numerically, for parameter values relevant to astrophysical plasmas. A numerical realization of magnetic turbulence is set up, in which the degree of anisotropy is varied by changing the correlation lengths l{sub x}, l{sub y}, and l{sub z}. The ratio {rho}/{lambda} of the particle Larmor radius {rho} over the turbulence correlation length {lambda} is also varied. It is found that for l{sub x},l{sub y}>>l{sub z}, and for {rho}/{lambda} < or approx. 10{sup -2} transport can be non-Gaussian, with superdiffusion along the average magnetic field and subdiffusion perpendicular to it. In addition, the spatial distribution of particles is clearly non-Gaussian. Such regimes are characterized by a Levy statistics, with diverging second-order moments. Decreasing the ratio l{sub x}/l{sub z}, nearly Gaussian (normal) diffusion is obtained, showing that the transport regime depends on the turbulence anisotropy. Changing the particle Larmor radius, normal diffusion is found for 10{sup -2} < or approx. {rho}/{lambda} < or approx. 1 because of increased pitch angle diffusion. New anomalous superdiffusive regimes appear when {rho}/{lambda} > or approx. 1 showing that the interaction between particles and turbulence decreases in thesemore »

- Authors:

- Physics Department, University of Calabria, Arcavacata di Rende, 87036 Rende (Italy)

- Publication Date:

- OSTI Identifier:
- 20960099

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2434795; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANISOTROPY; CHARGED PARTICLES; CORRELATIONS; DIFFUSION; LARMOR RADIUS; LENGTH; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; NUMERICAL ANALYSIS; PARTICLES; PLASMA; SPATIAL DISTRIBUTION; STATISTICS; TURBULENCE

### Citation Formats

```
Pommois, P., Zimbardo, G., and Veltri, P.
```*Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence*. United States: N. p., 2007.
Web. doi:10.1063/1.2434795.

```
Pommois, P., Zimbardo, G., & Veltri, P.
```*Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence*. United States. doi:10.1063/1.2434795.

```
Pommois, P., Zimbardo, G., and Veltri, P. Mon .
"Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence". United States.
doi:10.1063/1.2434795.
```

```
@article{osti_20960099,
```

title = {Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence},

author = {Pommois, P. and Zimbardo, G. and Veltri, P.},

abstractNote = {The transport of energetic particles in a mean magnetic field and in the presence of anisotropic magnetic turbulence is studied numerically, for parameter values relevant to astrophysical plasmas. A numerical realization of magnetic turbulence is set up, in which the degree of anisotropy is varied by changing the correlation lengths l{sub x}, l{sub y}, and l{sub z}. The ratio {rho}/{lambda} of the particle Larmor radius {rho} over the turbulence correlation length {lambda} is also varied. It is found that for l{sub x},l{sub y}>>l{sub z}, and for {rho}/{lambda} < or approx. 10{sup -2} transport can be non-Gaussian, with superdiffusion along the average magnetic field and subdiffusion perpendicular to it. In addition, the spatial distribution of particles is clearly non-Gaussian. Such regimes are characterized by a Levy statistics, with diverging second-order moments. Decreasing the ratio l{sub x}/l{sub z}, nearly Gaussian (normal) diffusion is obtained, showing that the transport regime depends on the turbulence anisotropy. Changing the particle Larmor radius, normal diffusion is found for 10{sup -2} < or approx. {rho}/{lambda} < or approx. 1 because of increased pitch angle diffusion. New anomalous superdiffusive regimes appear when {rho}/{lambda} > or approx. 1 showing that the interaction between particles and turbulence decreases in these cases. A new regime, called generalized double diffusion, is proposed for the cases when particles are able to trace back field lines. A summary of the physical conditions which lead to non-Gaussian transport is given.},

doi = {10.1063/1.2434795},

journal = {Physics of Plasmas},

number = 1,

volume = 14,

place = {United States},

year = {Mon Jan 15 00:00:00 EST 2007},

month = {Mon Jan 15 00:00:00 EST 2007}

}