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SUMMARY:Turbulence Acceleration - Dynamo mechanism by transport flow - Pro
 f Chang-Mo RYU (POSTECH\, Pohang\, Korea)
DTSTART:20090227T143000Z
DTEND:20090227T153000Z
UID:TALK17244@talks.cam.ac.uk
CONTACT:Christian Franzke
DESCRIPTION:A problem which is intimately related to solar radio bursts is
  the solar energetic\nelectrons. The in-situ detection of energetic electr
 ons of solar origin shows that the\ndistribution function almost invariabl
 y features enhanced energetic tails. In the\nliterature such a feature is 
 often modeled with the so-called kappa distribution. The\ntendency in the 
 literature is to treat the problem of particle acceleration/heating as a\n
 separate research topic from radio bursts problem. However\, the Langmuir 
 turbulence\ngeneration by the bump-on-tail instability (that eventually le
 ad to solar radio burst)\nand the electron acceleration problem are two di
 fferent manifestations of the same\nnonlinear and turbulent beam-plasma in
 teraction problem. The beam-plasma instability\nand Langmuir wave generati
 on takes place on the fastest time scale\, mode-coupling\nand radiation ge
 neration occurs over a longer time scale\, and the superthermal tail\nform
 ation takes place over a much longer time scale of quasi-stationary turbul
 ence\nregime\, the so-called turbulent quasi-equilibrium. In this talk\, I
  will discuss the recent\nresearch effort to understand the electron accel
 eration by beam-generated Langmuir\nturbulence.\n\n\nDynamo mechanism gene
 rating large scale magnetic fields in many astrophysical\nbodies as well a
 s in laboratory plasmas is still mysterious. I will talk about a new\nslow
  dynamo mechanism driven by transport flow. The distinguishing feature of 
 this\nnew mechanism compared to the conventional ones which are based on t
 he\nconvective flow lies in the intrinsic nature of the random flow motion
  to break the\nline-tying effect\, bringing in the net flux change. It is 
 shown that the anomalous\nplasma diffusion can induce a substantial amount
  of magnetic flux under certain\ncircumstances\, much greater than the res
 istive dissipation\, making the anomalous (or\nturbulence) transport flow 
 an attractive dynamo mechanism.
LOCATION:British Antarctic Survey\, Room 330B
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