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Title: Thermal island destabilization and the Greenwald limit

Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. In a fusion device, a magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration. 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. Further 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. An additional 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 near the plasmamore » 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:
; ;  [1]
  1. Plasma Physics Laboratory, Princeton University, P.O.Box 451, Princeton, New Jersey 08543 (United States)
Publication Date:
OSTI Identifier:
22408109
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CONFIGURATION; CURRENT DENSITY; ELECTRIC HEATING; ENERGY LOSSES; MAGNETIC ISLANDS; MAGNETIC RECONNECTION; PLASMA DENSITY; PLASMA IMPURITIES; RADIATIVE COOLING; SOLAR CORONA; THERMONUCLEAR DEVICES