Title: Thermal island destabilization and the Greenwald limit

Abstract

Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. A magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration is evident in a fusion device. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Furthermore, modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturated island. Because field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. In addition destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island nearmore » the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

Authors:

White, R. B.  ^[1];

• Search DOE PAGES for author "White, R. B."
• Search DOE PAGES for ORCID "0000-0002-4239-2685"

Gates, D. A.  ^[1];

• Search DOE PAGES for author "Gates, D. A."
• Search DOE PAGES for ORCID "0000-0001-5679-3124"

Brennan, D. P. ^[1]

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+ Show Author Affiliations

1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Publication Date:

Tue Feb 24 00:00:00 EST 2015

Research Org.:

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1254744

Alternate Identifier(s):

OSTI ID: 1228225

Report Number(s):

PPPL-5118
Journal ID: ISSN 1070-664X; PHPAEN

Grant/Contract Number:  

AC02-09CH11466

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 22; Journal Issue: 2; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Disruptions; Impurities; Magnetic Islands; Radiation Effects