Paper detail

The long hot summer of the tokamak

What have the probability for fine weather in summer and the possibility for a future use of nuclear fusion as a practically unlimited and clean energy source got in common? The answer is in the particular nature underlying both physical systems: both the atmosphere and hot magnetized fusion plasmas are determined by similar processes of structure formation in quasi-two-dimensional periodic nonlinear dynamical systems. Self-organization of waves and vortices on small scales in both cases leads to large-scale flows, which are, depending on conditions, either stable for a long time - or can break apart intermittently and expel large vortex structures. In the case of earth's atmosphere, a potential stabilization of the polar jet stream over northern Europe by warming in early summer leads to a high probability for stable hot midsummer weather in central Europe. The efficient utilization of nuclear fusion in a power plant also depends if a stabilization of such zonal flows ("H mode") may be sustained by heating of the plasma. However, instabilities may ruin by rain European summer holidays ("icelandic lows"), as well as lead to tempestuous eruptions ("ELMs") of energy and particles from the edge of a fusion plasma onto the walls of the reactor. In the latter case, this could cause strong erosion of the wall materials and thus an unefficient operation of a future fusion power plant. Plasma physicists are - similar to meteorologists - therefore interested in accurate predictions of these strongly nonlinear dynamical processes.