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2011
We report a first principles study of the coupled evolution of energetic ions, background majority ions, electrons and electromagnetic fields in magnetised plasma during the linear phase of the lower hybrid drift instability. A particle-incell code, with one spatial and three velocity space co-ordinates, is used to analyse the evolving distribution…
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2011
We present particle-in-cell (PIC) simulations of minority energetic protons in deuterium plasmas, which demonstrate a collective instability responsible for emission near the lower hybrid frequency and its harmonics. The simulations capture the lower hybrid drift instability in a regime relevant to tokamak fusion plasmas, and show further that the …
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2011
The overall phenomenology of plasmas emerges from multiple couplings between processes on many different lengthscales and timescales, creating innumerable feedback loops. For example, overall energy confinement – the central emergent property for fusion – is governed by a selfconsistent loop involving: temperature, density, and current profiles…
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2010
We present a novel code which solves the Vlasov-Fokker-Planck (VFP) equation in three dimensional magnetic turbulence using finite difference methods. The approach is distinct from particle tracking codes. The angular component of velocity space distribution function is represented by a spherical harmonic expansion drawing on an approach pioneered …
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2010
The effect of finite Larmor radius on the transport of passive charged test particles moving in turbulent electrostatic fields is investigated. The turbulent field is governed by a flexible model which is able to produce turbulence where zonal flows are damped or free to self-generate. A subtle interplay between trapping in small scale vortices and…
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2010
Wepresentgeneralizedstructurefunction(GSF)analysisof magneticandvelocityfieldfluctuationsmeasured insituinthesolarwindat ~ 1 AUwiththeACEspacecraft.Wedecomposethefluctuationsintodirectionsparalleland perpendiculartothemeanlocalbackgroundmagneticfield.GSFplotsbasedonthesequantitiesareshowntoprovideaclear indicatorofthespectralbreakbetweentheinertial…
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2009
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2009
Information theory, applied directly to measured signals, yields new perspectives on, and quantitative knowledge of, the physics of strongly nonlinear and turbulent phenomena in plasmas. It represents a new and productive element of the topical research programmes that use modem techniques to characterise strongly nonlinear signals from plasmas, an…
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2007
Direct numerical simulations DNS provide a means to test phenomenological models for the scaling properties of intermittent MHD turbulence. The well-known model of She and Leveque, when generalized to MHD, is in good agreement with the DNS in three dimensions, however, it does not coincide with DNS in two dimensions 2D. This is resolved here using …
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2006
Understanding the phenomenology captured in direct numerical simulation (DNS) of magnetohydrodynamic (MHD) turbulence rests upon models and assumptions concerning the scaling of field variables and dissipation. Here compressible MHD turbulence is simulated in two spatial dimensions by solving the isothermal equations of resistive MHD on a periodic …
Showing 41 - 50 of 87 UKAEA Paper Results