The Alpha Dynamo Effects in Laboratory Plasmas

Ji, Hantao ; Prager, Stewart C.

Princeton University. Plasma Physics Laboratory.

关键词: Electric Currents;    Magnetic Fields;    70 Plasma Physics And Fusion Technology;    71 Classical And Quantum Mechanics, General Physics;    Helicity;   

DOI  :  10.2172/788451
RP-ID  :  PPPL-3621
RP-ID  :  AC02-76CH03073
RP-ID  :  788451

美国|英语

来源: UNT Digital Library

【 摘 要 】

A concise review of observations of the alpha dynamo effect in laboratory plasmas is given. Unlike many astrophysical systems, the laboratory pinch plasmas are driven magnetically. When the system is overdriven, the resultant instabilities cause magnetic and flow fields to fluctuate, and their correlation induces electromotive forces along the mean magnetic field. This alpha-effect drives mean parallel electric current, which, in turn, modifies the initial background mean magnetic structure towards the stable regime. This drive-and-relax cycle, or the so-called self-organization process, happens in magnetized plasmas in a timescale much shorter than resistive diffusion time, thus it is a fast and unquenched dynamo process. The observed alpha-effect redistributes magnetic helicity (a measure of twistedness and knottedness of magnetic field lines) but conserves its total value. It can be shown that fast and unquenched dynamos are natural consequences of a driven system where fluctuations are statistically either not stationary in time or not homogeneous in space, or both. Implications to astrophysical phenomena will be discussed.