Sherwood 2015

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approvedmauel_poster_sherwood2015.pdf2015-03-13 14:41:44Mike Mauel

Toroidal Confinement without Parallel Current: Interchange and Entropy Modes in a Warm Electron Dipole Plasma

Author: Mike E. Mauel
Requested Type: Consider for Invited
Submitted: 2015-01-19 12:08:53

Co-authors: J.Kesner, D.Garnier, M.Roberts

Contact Info:
Columbia University
500 West 120th Street
New York, NY   10027

Abstract Text:
The axisymmetric magnetically levitated dipole guarantees omnigeneous particle drifts and is the only high-beta toroidal magnetic configuration that satisfies the Palumbo condition: the divergence of the perpendicular plasma current vanishes. The absence of parallel currents in a dipole-confined plasma is significant. Many tokamak instabilities, e.g. kink, tearing, ballooning, and drift modes, are not found in a plasma torus confined by a magnetic dipole [1]. Instead, interchange and entropy modes dominate plasma dynamics, and plasma profiles determine the level of turbulence. Turbulent transport causes centrally-peaked profiles and self-organization, as the plasma approaches a state of minimum entropy production [2,3]. These unique confinement and stability properties create a new paradigm of toroidal magnetic confinement and also link laboratory plasma confinement studies to the physics of planetary magnetospheres. Interchange mixing also appears in planetary magnetospheres driven by solar wind, but ionospheric currents regulate interchange motion in the magnetosphere [4]. The absence of field-aligned currents in the laboratory causes ion-inertial currents to set the global structure of low-frequency fluctuations. Measurements of electrostatic interchange and entropy modes in dipole-confined plasma show similiar global structures when driven either by energetic trapped electrons, sonic plasma rotation, or warm electron pressure. Recent experiments with localized current-injection feedback and with pellet injection show variations with mode frequency and amplitude that are consistent with linear and quasilinear models of interchange and entropy modes computed from the flux-tube averaged gyrofluid equations [5].

1. Garnier, et al., Phys Plasmas, 6, 3431 (1999).
2. Kesner, et al., Phys Plasmas, 18, 050703 (2011).
3. Kobayashi, at al, Phys Rev Lett, 105, 235004 (2010).
4. Lyon, Science, 288, 1987 (2000).
5. Ricci, et al., Phys Plasmas, 13, 062102 (2006).


March 16-18, 2015
The Courant Institute, New York University