Turbulence Acceleration - Dynamo mechanism by transport flow

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• Prof Chang-Mo RYU (POSTECH, Pohang, Korea)
• Friday 27 February 2009, 14:30-15:30
• British Antarctic Survey, Room 330B.

If you have a question about this talk, please contact Christian Franzke.

A problem which is intimately related to solar radio bursts is the solar energetic electrons. The in-situ detection of energetic electrons of solar origin shows that the distribution function almost invariably features enhanced energetic tails. In the literature such a feature is often modeled with the so-called kappa distribution. The tendency in the literature is to treat the problem of particle acceleration/heating as a separate research topic from radio bursts problem. However, the Langmuir turbulence generation by the bump-on-tail instability (that eventually lead to solar radio burst) and the electron acceleration problem are two different manifestations of the same nonlinear and turbulent beam-plasma interaction problem. The beam-plasma instability and Langmuir wave generation takes place on the fastest time scale, mode-coupling and radiation generation occurs over a longer time scale, and the superthermal tail formation takes place over a much longer time scale of quasi-stationary turbulence regime, the so-called turbulent quasi-equilibrium. In this talk, I will discuss the recent research effort to understand the electron acceleration by beam-generated Langmuir turbulence.

Dynamo mechanism generating large scale magnetic fields in many astrophysical bodies as well as in laboratory plasmas is still mysterious. I will talk about a new slow dynamo mechanism driven by transport flow. The distinguishing feature of this new mechanism compared to the conventional ones which are based on the convective flow lies in the intrinsic nature of the random flow motion to break the line-tying effect, bringing in the net flux change. It is shown that the anomalous plasma diffusion can induce a substantial amount of magnetic flux under certain circumstances, much greater than the resistive dissipation, making the anomalous (or turbulence) transport flow an attractive dynamo mechanism.

This talk is part of the British Antarctic Survey series.

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