Sherwood 2015

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approved2015paperabstract2.pdf2015-01-15 13:10:29Bruno Coppi

Role of Inertial and Inductive Modes in Magnetic Reconnection Events

Author: Bruno Coppi
Requested Type: Consider for Invited
Submitted: 2015-01-15 13:07:04

Co-authors: B.Basu, P,Montag

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Abstract Text:
Recently, an accurate analysis of the database of magnetic island rotation performed with the JET machine [1] has revealed that, in the frame of zero radial electric field, the island rotation frequency is about 〖0.9ω〗_di, where ω_di is the ion diamagnetic frequency. The drift-tearing mode theory of reconnection in low collisionality regimes predicts a phase velocity in the opposite direction [2] and, under strictly collisionless conditions, stability in the presence of electron temperature gradients [3]. To explain the observations, a “mode inductivity” L_(||)≡(4π⁄c^2 )S_L has been introduced [4] whose effects replace those of finite resistivity. This has led to a linear instability [5] with ω close to ω_di. The reconnection layer thickness is proportional to the inductivity [4] and the mode has a dissipative growth rate. When considering plasmas with ultrarelativistic energies, the inertial skin depth c⁄ω_pe becomes significant. However, if c^2⁄(ω_pe^2 ) is the only contribution to S_L, the class of reconnecting modes that must be considered are those close to ideal MHD marginal stability [6]. In this case the width of the reconnection layer is of the order of the inertial skin depth and can be considered as relevant to realistic theories.

[1] P. Buratti et al., 2014 "Magnetic islands rotation in JET", 41st EPS Conference on Plasma Physics (Berlin 2014) ECA vol. 38F, paper P1.014.
[2] B. Coppi, Phys. Fluids 8, (1965) 2273.
[3] B. Coppi, L. Sugiyama, et al., Ann. Phys. 119, (1979) 370.
[4] B. Coppi, Bull. Am. Phys. Soc. 45, (2000) 366.
[5] B. Coppi, B. Basu, P. Montag, L. Sugiyama, T. Zhou, and P. Buratti, Paper presented at the 2014 IAEA Int. Fus. En. Conf. (St. Petersburg, 2014) TH-P7/10; submitted to Nucl. Fusion.
[6] B. Coppi, R. Galvao, R. Pellat, M. Rosenbluth, and P. Rutherford, Fiz. Plazmy 2, (1976) 961 [Sov. J. Plasma Phys. 2, (1976) 533].


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