# Publications

## Improved beta (local beta > 1) and density in electron cyclotron resonance heating on the RT-1 magnetosphere plasma

Nuclear Fusion **55** (2015)

© 2015 IAEA. This study reports the recent progress in improved plasma parameters of the RT-1 device. Increased input power and the optimized polarization of electron cyclotron resonance heating (ECRH) with an 8.2 GHz klystron produce a significant increase in electron beta, which is evaluated by an equilibrium analysis of the Grad-Shafranov equation. The peak value of the local electron beta β < inf > e < /inf > is found to exceed 1. In the high-beta and high-density regime, the density limit is observed for H, D and He plasmas. The line-averaged density is close to the cutoff density for 8.2 GHz ECRH. When the filling gas pressure is increased, the density limit still exists even in the low-beta region. This result indicates that the density limit is caused by the cutoff density rather than the beta limit. From the analysis of interferometer data, we found that inward diffusion causes a peaked density profile beyond the cutoff density.

## Measurement of a density profile of a hot-electron plasma in RT-1 with three-chord interferometry

Physics of Plasmas **22** (2015)

© 2015 AIP Publishing LLC. The electron density profile of a plasma in a magnetospheric dipole field configuration was measured with a multi-chord interferometry including a relativistic correction. In order to improve the accuracy of density reconstruction, a 75 GHz interferometer was installed at a vertical chord of the Ring Trap 1 (RT-1) device in addition to previously installed ones at tangential and another vertical chords. The density profile was calculated by using the data of three-chord interferometry including relativistic effects for a plasma consisting of hot and cold electrons generated by electron cyclotron resonance heating (ECH). The results clearly showed the effects of density peaking and magnetic mirror trapping in a strongly inhomogeneous dipole magnetic field.

## Non-linear mirror instability

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY **447** (2015) L45-L49

## The impact of accretion disc winds on the optical spectra of cataclysmic variables

Monthly Notices of the Royal Astronomical Society **450** (2015) 3331-3344

## Gas flow in barred potentials

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY **449** (2015) 2421-2435

## Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY **450** (2015) 4184-4197

## Less constrained omnigeneous stellarators

NUCLEAR FUSION **55** (2015) ARTN 033005

## Relabeling symmetry in relativistic fluids and plasmas

Journal of Physics A: Mathematical and Theoretical **47** (2014)

© 2014 IOP Publishing Ltd. The conservation of the recently formulated relativistic canonical helicity (Yoshida et al 2014 J. Math. Phys. 55 043101) is derived from Noether's theorem by constructing an action principle on the relativistic Lagrangian coordinates (we obtain general cross helicities that include the helicity of the canonical vorticity). The conservation law is, then, explained by the relabeling symmetry pertinent to the Lagrangian label of fluid elements. Upon Eulerianizing the Noether current, the purely spatial volume integral on the Lagrangian coordinates is mapped to a space-time mixed three-dimensional integral on the four-dimensional Eulerian coordinates. The relativistic conservation law in the Eulerian coordinates is no longer represented by any divergence-free current; hence, it is not adequate to regard the relativistic helicity (represented by the Eulerian variables) as a Noether charge, and this stands the reason why the 'conventional helicity' is no longer a constant of motion. We have also formulated a relativistic action principle of magnetohydrodynamics (MHD) on the Lagrangian coordinates, and have derived the relativistic MHD cross helicity.

## Relativistic helicity and link in Minkowski space-time

Journal of Mathematical Physics **55** (2014)

A relativistic helicity has been formulated in the four-dimensional Minkowski spacetime. Whereas the relativistic distortion of space-time violates the conservation of the conventional helicity, the newly defined relativistic helicity conserves in a barotropic fluid or plasma, dictating a fundamental topological constraint. The relation between the helicity and the vortex-line topology has been delineated by analyzing the linking number of vortex filaments which are singular differential forms representing the pure states of Banach algebra. While the dimension of space-time is four, vortex filaments link, because vorticities are primarily 2-forms and the corresponding 2- chains link in four dimension; the relativistic helicity measures the linking number of vortex filaments that are proper-time cross-sections of the vorticity 2-chains. A thermodynamic force yields an additional term in the vorticity, by which the vortex filaments on a reference-time plane are no longer pure states. However, the vortex filaments on a proper-time plane remain to be pure states, if the thermodynamic force is exact (barotropic), thus, the linking number of vortex filaments conserves. © 2014 AIP Publishing LLC.

## The Gaia-ESO Survey: processing FLAMES-UVES spectra

ASTRONOMY & ASTROPHYSICS **565** (2014) ARTN A113

## Erratum: "Correlations at large scales and the onset of turbulence in the fast solar wind" (2013, ApJ, 778, 177)

Astrophysical Journal **782** (2014)

## Actions, angles and frequencies for numerically integrated orbits

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY **441** (2014) 3284-3295

## Bayes versus the virial theorem: inferring the potential of a galaxy from a kinematical snapshot

Monthly Notices of the Royal Astronomical Society **437** (2014) 2230-2248

I present a new framework for estimating a galaxy's gravitational potential, Phi, from its stellar kinematics. It adopts a fully non-parametric model for the galaxy's unknown phase-space distribution function, f, that takes full advantage of Jeans' theorem. Given an expression for the joint likelihood of Phi and f, the likelihood of Phi is calculated by using a Dirichlet process mixture to represent the prior on f and marginalising. I demonstrate that modelling machinery constructed using this framework is successful at recovering the potentials of some simple systems given perfect kinematical data, a situation handled effortlessly by traditional moment-based methods, such as the virial theorem, but in which the more modern extended-Schwarzschild method fails. Unlike moment-based methods, however, the models constructed using this framework can easily be generalised to take account of realistic observational errors and selection functions.

## The effect of diamagnetic flows on turbulent driven ion toroidal rotation

PHYSICS OF PLASMAS **21** (2014) ARTN 056106

## Constraining the Galaxy's dark halo with RAVE stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY **445** (2014) 3133-3151

## A NEW STELLAR CHEMO-KINEMATIC RELATION REVEALS THE MERGER HISTORY OF THE MILKY WAY DISK

ASTROPHYSICAL JOURNAL LETTERS **781** (2014) ARTN L20

## Galactic kinematics and dynamics from Radial Velocity Experiment stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY **439** (2014) 1231-1244

## Reduction of core turbulence in I-mode plasmas in Alcator C-Mod

NUCLEAR FUSION **54** (2014) ARTN 083019

## LINE-DRIVEN DISK WINDS IN ACTIVE GALACTIC NUCLEI: THE CRITICAL IMPORTANCE OF IONIZATION AND RADIATIVE TRANSFER

The Astrophysical Journal **789** (2014) 19-19

## Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas

Plasma Physics and Controlled Fusion **56** (2014)

Observations of ion-scale (k y ρ i 1) density turbulence of relative amplitude 0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging beam emission spectroscopy diagnostic. Spatial and temporal charac teristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplitude and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be 'critically balanced', the simulated turbulence is weak. © 2014 IOP Publishing Ltd.