arXiv subjects

Shaojie Wang

Publications and source records attributed to Shaojie Wang.

40 records · Page 3Linked to original sources

arXiv2014

Parallel acceleration due to the radial electric field in a magnetized plasma with low-frequency turbulence

A new physical mechanism of the parallel acceleration of a turbulent magnetized plasma is discovered by using a Fokker-Planck phase space stochastic transport equation. It is found that the random walk of a charged particle is correlated with the random change of the parallel velocity due to the radial electric field and the magnetic moment conservation. This correlation leads to a parallel acceleration of the plasma with a finite parallel fluid flow.

physics.plasm-ph↗

arXiv2014

Co-current rotation of the bulk ions due to the ion orbit loss at the edge of a tokamak plasma

Flux-surface-averaged momentum loss and parallel rotation of the bulk ions at the edge of a tokamak plasma due to the ion orbit loss are calculated by computing the minimum loss energy of both the trapped and the passing thermal ions. The flux-surface-averaged parallel rotation of the bulk ions is in the co-current direction. The peak of the co-current rotation speed locates inside the last closed flux surface due to the orbit loss of the co-current thermal ions at the very edge of a tokamak plasma. The peaking position moves inward when the ion temperature increases.

physics.plasm-ph↗

arXiv2014

From Liouville's theorem to quasilinear, nonlinear stochastic, and fractional transport, a multi-scale kinetics of plasma turbulence

From Liouville's equation, a phase-space multi-scale transport equation is systematically derived. The proposed phase-space multi-scale transport equation based on the first principle indicates that the nonlinear stochastic transport is due to the micro-turbulence scattering while the familiar quasilinear transport is due to the long-range correlation of the meso-scale coherent modes; and more interestingly, it demonstrates a systematic derivation of the fractional transport equation that may provide a new view-angle to understand the anomalous transport observed in plasma turbulence. The multi-scale kinetics suggests a new approach to confinement improvement through the formation of nonlinearly self-organized stable large-scale structures.

physics.plasm-ph↗

arXiv2013

On the kinetic theory of turbulence in plasmas

From the nonlinear (NL) Vlasov equation, a NL turbulence scattering term is found to describe the stochastic dissipation on the time scale longer than the turbulence correlation time. The evolution of the plasma distribution is determined by the well-understood unperturbed motion of charged particles, with the effects of fluctuating part of fields described by the turbulence scattering term. In the new framework, one can identify various important physics, covering from the linear and quasilinear to the NL regime; in particular, the connections between the widely used Kadomtsev-Pogutse's equation and Frieman-Chen's equation. The NL scattering term indicates the Onsager symmetry relation of turbulent transport and a NL frequency or k spectrum shift of a resonantly excited wave.

physics.plasm-ph↗