An ‘ideal’ form of decaying two-dimensional turbulence

In decaying two-dimensional Navier–Stokes turbulence, Batchelor's similarity hypothesis fails due to the existence of coherent vortices. However, it is shown that decaying two-dimensional turbulence governed by the Charney–Hasegawa–Mima (CHM) equation (∂/∂t)(∇2φ−λ2φ) +J(φ, ∇2φ) = D, where D is a damping, is described well by Batchelor's similarity hypothesis for wave numbers k [Lt ] λ (the so-called AM regime). It is argued that CHM turbulence in the AM regime is a more ‘ideal’ form of two-dimensional turbulence than is Navier–Stokes turbulence itself.