Fluctuations in Multipole Confined Plasmas

We propose an explanation for different types of fluctuations observed in multipole experiments based on a new formal solution of the general integral equation that yields, besides the known hydromagnetic mode types, modes with frequency smaller than the average ion slow-excursion frequency. The relevant modes are of flute type, have frequency range and phase velocity in agreement with observation, and become almost purely growing and unlikely to be observed as fluctuations in conditions where these have not been detected.