In some cases strongly toroidally and poloidally asymmetric structures emerge in tokamak plasmas, which crucially alter plasma transport making it more convective rather than diffusive.For example, experimental data [1] suggest that fast radial plasma transport in the tokamak scrape-off Layer (SOL) may be associated with coherent structures (blobs) that separate from the main plasma and convect outward [2]. Similar structures have also been observed in other devices, such as stellarators and linear plasma mashines [3] which can be associated either with centrifular force or with neutral wind effects [4]. In addition, very recent experiments suggest that edge localized modes (ELM) show convective behavior in the SOL in a manner rather similar to that of blob [5]. Analytic theory of explosive instability [6] may be related to ELM dynamics. Another example is the evolution of pellet plasma cloud [7] which also exhibits convective transport features. Here we argue that many essentials of blobs, ELMs, and pellet cloud dynamics can be described by rather simple model, which include plasma polarization due to inertia and curvature, centrifugal, or neutral wind effects and polarization damping due to either Alfven wave generation or sheath effects.

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