A limitation to the analogy between pure electron plasmas and two-dimensional inviscid fluids

Thermal corrections to E×B drifts cause small structures in pure electron plasmas to smear. This smearing breaks the strict analogy between the behavior of pure electron plasmas and the behavior of two-dimensional inviscid fluids. The causes and consequences of this smearing are discussed, a criterion for the validity of the plasma/fluid analogy is constructed, and experimental examples of the failure of the analogy are presented. The criterion indicates that fluid-like behavior can persist to scale lengths far smaller than the normal ‘‘collective’’ behavior limit.