Enstrophy non-conservation and the forward cascade of energy in two-dimensional electrostatic magnetized plasma turbulence
Abstract
A fluid system is derived to describe electrostatic magnetized plasma turbulence at scales somewhat larger than the Larmor radius of a given species. It is related to the Hasegawa-Mima equation, but does not conserve enstrophy, and, as a result, exhibits a forward cascade of energy, to small scales. The inertial-range energy spectrum is argued to be shallower than a $-11/3$ power law, as compared to the $-5$ law of the Hasegawa-Mima enstrophy cascade. This property, confirmed here by direct numerical simulations of the fluid system, may help explain the fluctuation spectrum observed in gyrokinetic simulations of streamer-dominated electron-temperature-gradient driven turbulence (Plunk et al., Phys. Rev. Lett., vol. 122, 2019, 035002), and also possibly some cases of ion-temperature-gradient driven turbulence where zonal flows are suppressed (Plunk et al., Phys. Rev. Lett., vol. 118, 2017, 105002).
- Publication:
-
Journal of Plasma Physics
- Pub Date:
- August 2020
- DOI:
- 10.1017/S0022377820000872
- arXiv:
- arXiv:2008.03018
- Bibcode:
- 2020JPlPh..86d1702P
- Keywords:
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- fusion plasma;
- plasma dynamics;
- plasma nonlinear phenomena;
- Physics - Plasma Physics
- E-Print:
- doi:10.1017/S0022377820000872