### Abstract

The probability distribution functions (PDFs) of momentum flux and zonal flow formation in ion-temperature-gradient (ITG) turbulence are investigated in two different models. The first is a general five-field model (n_{i}, , T_{i},φT_{e}, v_{i∥}) where a reductive perturbation method is used to derive dynamical equations for drift waves and a zonal flow. The second is a reduced two-field model (φ, T_{i}) that has an exact non-linear solution (bipolar vortex soliton). In both models the exponential tails of the zonal flow PDFs are found with the same scaling (PDF ∼ exp{?cZFφ^{3}ZF}), but with different coefficients c _{ZF}. The PDFs of momentum flux is, however, found to be qualitatively different with the scaling (PDF ∼ exp{-c_{M}R^{s}}), where s = 2 and s = 3/2 in the five and two-field models, respectively.

Original language | English |
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Article number | 075027 |

Journal | Nuclear Fusion |

Volume | 49 |

Issue number | 7 |

DOIs | |

Publication status | Published - 1 Jul 2009 |

Externally published | Yes |

### ASJC Scopus subject areas

- Condensed Matter Physics
- Nuclear and High Energy Physics