Solving numerically the integro-differential equation for plasma oscillations, the authors study the effect of the size of the ion Larmor radius ri and of an intrinsic electric field on the flute instability of a plasma. It is shown that, in a dilute plasma (, where ω0i and ωi, are the plasma and Larmor frequencies of the ions), effects attributable to the finiteness of ri are small and cannot explain the stabilization of oscillations in the Phoenix device. Intrinsic electric fields due to an excess of ions improve the stability of such a plasma. If the magnetic field gradient is small (aH'/H ∼ 0.1, where a is the characteristic dimension of the plasma) and the Larmor radius is of reasonable size (ri ∼ 0.2a). a relatively dense plasma surrounded by a conducting sheath may be stable.