AN ENERGY ESTIMATE FOR A PERTURBED HASEGAWA-MIMA EQUATION

It is commonly believed that drift waves and drift-wave turbulence pla y a major role in the understanding of anomalous transport at the plas ma edge of a tokamak fusion reactor. A one-field equation describing t he electrostatic potential fluctuations in this regime is the so-calle d Hasegawa-Mima equation. If this equation is driven by some instabili ty and damped by some hyperviscous term, the energy grows exponentiall y in time which is not consistent with the approximations made in the derivation of the equation. Numerical simulations of a perturbed Haseg awa-Mima equation which includes in addition a so-called E x B nonline arity showed that the energy saturates at a finite level. Ir. this pap er this numerical observation is proven analytically.