Research Plan

• Year 1: Explore secondary instabilities near the magnetic X-line during the sawtooth crash with a fixed magnetic island, using analytic analysis and with gyrokinetic code(s).
• Year 2: Explore the nonlinear development of secondary instabilities and and the development of a turbulent front around the X-line. Again at a fixed island with gyrokinetic code(s). Comparison with fluctuation data during the sawtooth crash on NSTX and DIII-D.
• Year 3: Explore the development of turbulence with an evolving magnetic island using BATS-R-US to evolve the external MHD solution and gyrokinetics to evolve an annulus around the X-line using projective integration. Continue comparison with experimental sawtooth fluctuation data.
• Year 4: Explore complete crash with self-consistent development of turbulence. Compare the relative roles of large scale convection and turbulent transport in driving energy expulsion from the core during the sawtooth crash. Continue comparisons with experiment.
• Year 5: Explore the influence of plasma shape on the development of the sawtooth crash and the final state of the central q profile.

Key personnel and their roles

The attack on the sawtooth crash problem involves MHD and gyrokinetic computations, experimental observations and analysis. Jim Drake will play the leadership role on this project. Experimental comparisons will be led by Buttery (JET) and La Haye (GA). In the early phases of the effort MHD modeling of the early phase of the crash will be carried by the Michigan group led by Tamas Gombosi. The stability of the resulting island state and associated steep gradients will be explored with analytic analysis and gyrokinetic simulation. Steve Cowley, Drake and Rogers will focus on the analysis with Dorland taking the lead on the simulations. Nonlinear gyrokinetic simulations will be coupled to MHD external solutions obtained from BATS-R-US. In parallel with these activities, Shay and Dorland with Kevrekidis and Gear will develop p3d and GS2 as the timestepping kernels for a projective integrator appropriate for the reconnection problem.