Stochastic analysis of subcritical amplification of magnetic energy in a turbulent dynamo

Sergei Fedotov, Irina Bashkirtseva, Lev Ryashko

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We present and analyze a simplified stochastic αΩ-dynamo model which is designed to assess the influence of additive and multiplicative noises, non-normality of dynamo equation, and nonlinearity of the α-effect and turbulent diffusivity, on the generation of a large-scale magnetic field in the subcritical case. Our model incorporates random fluctuations in the α-parameter and additive noise arising from the small-scale fluctuations of magnetic and turbulent velocity fields. We show that the noise effects along with non-normality can lead to the stochastic amplification of the magnetic field even in the subcritical case. The criteria for the stochastic instability during the early kinematic stage are established and the critical value for the intensity of multiplicative noise due to α-fluctuations is found. We obtain numerical solutions of nonlinear stochastic differential equations and find the series of phase transitions induced by random fluctuations in the α-parameter.

    Original languageEnglish
    Pages (from-to)491-506
    Number of pages16
    JournalPhysica A: Statistical Mechanics and its Applications
    Volume342
    Issue number3-4
    DOIs
    Publication statusPublished - 1 Nov 2004

    Keywords

    • Magnetic field
    • Non-normality
    • Stochastic amplification

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