Properties of freely decaying and driven turbulence of fusion plasmas using gyrokinetic particle simulation
In a recent work, the effects of nonlinear self-consistent profile relaxation on the ITG turbulence in global delta-f particle simulations were studied [1] using Gyrokinetic Toroidal Code (GTC) [2]. In contrast to several other gyrokinetic turbulence models, GTC shows that the turbulence is insensitive to minute or drastic profile changes and reaches the similar flux levels irrespective of whether or not it is a driven or freely decaying turbulence. In the present work, we address the spectral properties of gyrokinetic turbulence and argue that correct inclusion of parallel velocity space nonlinearity may bring forth certain important late-time features such as Geodesic Acoustic Modes like (GAM) structures.
A Fourier-Hermite Study of Dissipation in 1+1-D Models of Fusion Plasmas
This study investigates dissipation in fusion plasmas confined by strong magnetic fields, as described by 5-D gyrokinetic theory. We first derive a reduced model for the dynamics parallel to the magnetic field in both physical and velocity spaces. This model closely resembles the classic one-dimensional Vlasov-Poisson system, but replaces Poisson’s law with the quasineutrality condition relevant to multi-species fusion plasmas. We construct a numerical model using a truncated Fourier-Hermite representation, validate it against existing results for the Vlasov-Poisson system, and then apply it to fusion plasmas. Similarities and differences between the classic and fusion cases are assessed. We then investigate the effect of unsteady forcing by a neutral particle beam, representing both an actual tokamak energy source and a model for turbulence in the omitted dimensions perpendicular to the magnetic field. We find that even small amplitude forcing may substantially affect the long-time behavior, which may have important consequences in the design of efficient fusion reactors.
Pioneer 10 Observations of the Ultraviolet Glow in the Vicinity of Jupiter
A two-channel ultraviolet photometer aboard Pioneer 10 has made several observations of the ultraviolet glow in the wavelength range from 170 to 1400 angstroms in the vicinity of Jupiter. Preliminary results indicate a Jovian hydrogen (1216 angstrom) glow with a brightness of about 1000 rayleighs and a helium (584 angstrom) glow with a brightness of about 10 to 20 rayleighs. In addition, Jupiter appears to have an extensive hydrogen torus surrounding it in the orbital plane of Io. The mean diameter of the torus is about equal to the diameter of the orbit of Io. Several observations of the Galilean satellites have also occurred but only a rather striking Io observation has been analyzed to date. If the observed Io glow is predominantly that of Lyman-α, the surface brightness is about 10,000 rayleighs.