The influence of fishbones on the background plasma

Observations on ASDEX Upgrade show that fishbones can have a much stronger effect on the background plasma parameters than expected from an ideal, fas t particle driven instability. They lead to a redistribution of electron te mperature and impurity densities, similar in form and magnitude to sawteeth , albeit with the plasma parameter variation occurring on a significantly l onger time-scale. Simulations of the current diffusion in discharges with f avourable core confinement require fishbones to be furthermore associated a lso with magnetic reconnection to yield consistency between the conductivit y and current profile information derived from ECE, bremsstrahlung MSE and the localization of m = 1, n = 1 activity.