R. G. L. Vann R. O. Dendy M. P. Gryaznevich
Frequency sweeping (chirping) of high frequency magnetohydrodynamic modes is widely observed in tokamak plasmas. In this paper observations of chirping in neutral-beam-heated plasmas in the Mega-Amp Spherical Tokamak (MAST) [A. Sykes, R. J. Akers, L. C. Appel and et al. , Nucl. Fusion 41 , 1423 (2001)] are considered, and it is shown that these may…
PublishedJ. A. Merrifield W.-C. Müller S. C. Chapman R. O. Dendy
The statistical properties of the dissipation process constrain the analysis of large scale numerical simulations of three-dimensional incompressible magnetohydrodynamic ( MHD ) turbulence, such as those of Biskamp and Müller [ Phys. Plasmas 7 , 4889 ( 2000 )] . The structure functions of the turbulent flow are expected to display statistical self…
PublishedC. Courtois R.A.D. Grundy A.D. Ash D.M. Chambers N.C. Woolsey R.O. Dendy K.G. McClements
Results from an experimental study of the collisionless interaction of two laser-produced plasmas in a magnetic field with applications to supernova remnant shock physics are presented. The dynamics of the two plasmas and their interaction are studied with and without magnetic field through spatially and temporally resolved measurements of the elec…
PublishedT.K. March S.C. Chapman R.O. Dendy J. A. Merrifield
Previous observations that suggest a substantial role for nondiffusive energy transport in tokamaks subjected to off-axis electron cyclotron heating (ECH) are compared to the output from a sandpile model. The observations considered include local and global aspects of temperature profile evolution in the DIII-D [for example, C. C. Petty and T. C. L…
PublishedR. E. Lee S. C. Chapman R. O. Dendy
The identification of preacceleration mechanisms for cosmic ray ions in supernova remnant shocks is an important problem in astrophysics. Recent particle-in-cell ( PIC ) shock simulations have shown that inclusion of the full electron kinetics yields non-time-stationary solutions, in contrast to previous hybrid ( kinetic ions, fluid electrons ) sim…
PublishedN. J. Sircombe T. D. Arber R. O. Dendy
Direct numerical simulations of electron dynamics in externally driven electrostatic waves have been carried out using a relativistic two-fluid one-dimensional Vlasov–Poisson code. When the driver wave has sufficiently large amplitude, ion density holes ( cavitons ) form. The interaction between these cavitons and other incoming Langmuir waves gi…
PublishedN.C. Woolsey A.D. Ash D.M. Chambers C. Courtois R.O. Dendy R.A.D. Grundy K.G. McClements
Laboratory astro-plasma physics experiments are being designed to advance both our astrophysics and plasma physics knowledge. With current laser technology, target design and diagnostics, it is now possible to reproduce and measure the conditions of temperature and pressure usually met in extreme stellar environments. Coupled with scaled plasma phy…
PublishedD. Hughes M. Paczuski R.O. Dendy P. Helander K.G. McClements
A model for the solar coronal magnetic field is proposed where multiple directed loops evolve in space and time. Loops injected at small scales are anchored by footpoints of opposite polarity moving randomly on a surface. Nearby footpoints of the same polarity aggregate, and loops can reconnect when they collide. This may trigger a cascade of furth…
PublishedR. G. L. Vann R. O. Dendy G. Rowlands T. D. Arber N. D’Ambrumenil
The Berk–Breizman augmentation of the Vlasov–Maxwell system is widely used to model self-consistent resonant excitation and damping of wave fields by evolving energetic particle populations in magnetic fusion plasmas. The key model parameters are the particle annihilation rate, which drives bump-on-tail structure, and the linear wave damping ra…
PublishedJ. Greenhough S.C. Chapman R.O. Dendy V.M. Nakariakov G. Rowlands
We investigate the distribution of fluctuations in solar irradiance when integrated over the full disk, obtained using extreme ultraviolet / soft X-ray observations from the SOHO CELIAS / SEM instrument. This time series sums over both the contributions of single distinguishable flares, and of many other processes. By detrending we select events wi…
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