Using the compressible resistive MHD equations in a finite aspect ratio cylinder, it is found that the m = 1 mode (the sawtooth oscillation) can saturate when the pressure inside the magnetic island is higher than that of tha original core plasma. The saturation condition is cf the form As_ > 8 E"1^ {1 -q 0 ) 2 . This saturation effect can be used to actively stabilize sawteeth by heating the island and/or by cooling the core plasma. This mechanism together with a stabilizing toroidal effect

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... also explain recent lower-hybrid-wave-driven tokaraak experiments where the saturation of sawteeth has been observed. MASTER 4# DISTRIBUTION OF THIS DOCUMENTS UNLIMITED a density source will somewhat change the time scales of local phenomena, but not the overall physics. This approximation significantly reduces the complexity of the equations and also greatly enhances the numerical accuracy of the calculation. The heat conduction term is not solved by a direct method because the large K., (>C. >> <.) causes a large numerical error. Instead this term is solved using the artificial parallel velocity method described in Ref. 12. This gives the B«vp = 0 condition in an efficient way. By setting x = o in the above equations, the incompressible helical MHD equations > can be obtained. He wish to thank Drs. A.