In a linearl=1 stellarator [Phys. Fluids30, 2885 (1987)] internal probes are used to measure the structure and temporal behavior of the plasma and magnetic field. At lower densities (and higher temperatures) diffuse‐profile equilibria are produced that are perturbed by ak≊0 oscillation. At higher densities (and lower temperatures) sharp‐boundary plasmas are produced that are unstable with an exponentially growingm=1,k≊0 mode. Finite Larmor radius (FLR) effects are adduced to explain the absence of the instability in the oscillatory regime.