MHD stability analysis of high beta JET discharges

The theoretical stability of high- beta JET discharges is discussed. For discharges near the beta limit, a significant fraction of the core is found to be marginally stable to high-n ballooning modes. For low-n internal modes (n=1 and 2) the theoretical predictions are found to correlate well with the experimentally observed soft X-ray behaviour, and provide a basis for predicting the central q-profile.