[en] Fluctuations and anomalous particle loss of a xenon afterflow plasma, which appear immediately after the decay of convective cells in an l = 3 stellarator, are investigated experimentally. This instability is caused by a static electric field directed into plasma. The fluctuation propagates in the direction of the E vector₀ x B vector₀ rotation, which is parallel to the electron diamagnetic current, and is expressed as exp[i(mtheta + nphi -ωt)], m = 2 and n = -1, where theta is measured in the poloidal and phi in the toroidal direction. A dispersion relation is derived from a model in which there is a difference of rotation velocity between ions and electrons, and the electron-ion collision in the electron motion parallel to the magnetic field is included. The difference in rotation velocities comes from the effect of finite ion Larmor radius and the centrifugal force. The dispersion relation derived here also includes the resistive drift instability. The growth rate takes maximum values on the rational magnetic surfaces. Predictions on the basis of the dispersion relations are in good agreement with observed wave propagation, frequency, growth rate, and plasma loss. (author)