Convective cell formation and spectral cascade processes due to gravitational drift Alfve´n waves are studied using a new type of model equation. Conservation relations are derived and explosive instability is found for systems near marginal finite &bgr; stability. This instability also remains when the effects of poor as well as favorable curvature regions are included, i.e., for ballooning modes. The anomalous diffusion due to convective cells and quasi‐linear effects are compared.