Measurement of the dynamo effect in a plasma

H. ji, S. C. Prager, A. F. Almagri, J. S. Sarff, Y. Yagi, Y. Hirano, K. Hattori, H. Toyama

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

A series of detailed experiments has been conducted in three laboratory plasma devices to measure the dynamo electric field along the equilibrium field line (the α effect) arising from the correlation between the fluctuating flow velocity and magnetic field. The fluctuating flow velocity is obtained from probe measurement of the fluctuating E×B drift and electron diamagnetic drift. The three major findings are the following: (1) The α effect accounts for the dynamo current generation, even in the time dependence through a ‘‘sawtooth’’ cycle; (2) at low collisionality the dynamo is explained primarily by the widely studied pressureless magnetohydrodynamic (MHD) model, i.e., the fluctuating velocity is dominated by the E×B drift; (3) at high collisionality, a new ‘‘diamagnetic dynamo’’ is observed, in which the fluctuating velocity is dominated by the electron diamagnetic drift. In addition, direct measurements of the helicity flux indicate that the dynamo activity transports magnetic helicity from one part of the plasma to another, but the total helicity is roughly conserved, verifying Taylor's [Phys. Rev. Lett. 33, 1139 (1974); Rev. Mod. Phys. 58, 741 (1986)] conjecture.

Original languageEnglish (US)
Pages (from-to)1935-1942
Number of pages8
JournalPhysics of Plasmas
Volume3
Issue number5
DOIs
StatePublished - May 1996

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Keywords

  • FLUCTUATIONS
  • HELICITY
  • MAGNETIC FLUX
  • MAGNETOHYDRODYNAMICS
  • OHM LAW
  • PLASMA DRIFT
  • REVERSE−FIELD PINCH
  • TURBULENCE

Fingerprint Dive into the research topics of 'Measurement of the dynamo effect in a plasma'. Together they form a unique fingerprint.

  • Cite this

    ji, H., Prager, S. C., Almagri, A. F., Sarff, J. S., Yagi, Y., Hirano, Y., Hattori, K., & Toyama, H. (1996). Measurement of the dynamo effect in a plasma. Physics of Plasmas, 3(5), 1935-1942. https://doi.org/10.1063/1.871989