Plasma Physics

Effect of Dust Particle Growth on the Emission Spectrum of a Complex Plasma

by Brett Layden

Residual Dust Charges in a Complex Plasma Afterglow

by Brett Layden

Dynamics of Coronal Mass Ejections in the interplanetary medium: an analytic perspective

by Pedro Corona-Romero

Co-authored with J.A. Gonzalez-Esparza. Draft in preparation for Journal of Geophysical Research.

We present a study about the posible forces, according the magnetohidrodynamics theory, goberning the propagation of... more We present a study about the posible forces, according the magnetohidrodynamics theory, goberning the propagation of coronal mass ejections (CMEs) along their propagation thorugh interplanetary (IP) medium. Such forces arise from the interaction between the CME and the ambient solar wind (SW). We also compare and discuss of some analytic approches to modeling the CME-SW dynamic coupling.

Dynamic evolution of Interplanetary Shock Waves driven by CMEs

by Pedro Corona-Romero

Co-authored with J.A. Gonzalez-Esparza. Proceedings IAU Symposium No. 286, 2011.

We present a study about the propagation of interplanetary shock waves driven by super magnetosonic coronal mass... more We present a study about the propagation of interplanetary shock waves driven by super magnetosonic coronal mass ejections (CMEs). The discussion focus on a model which discribes the dynamic relationship between the CME and its driven shock and the way to approximate the trajectory of shocks based on those relationships from near the Sun to 1 AU. We apply the model in the analysis of a study case, in which our calculations show quantitative and cualitative agreements with different kind of data. We discuss the importance of solar wind and CME initial conditions on the shock wave evolution.

Determination of plasma parameters in the PUPR mirror and cusp plasma machine via electrostatic probe methods

by Angel Gonzalez-Lizardo

Study on plasma creation and propagation in a pulsed magnetoplasmadynamic thruster

by Tony Schönherr

World Academy of Science, Engineering and Technology

The performance and the plasma created by a pulsed magnetoplasmadynamic thruster for small satellite application is... more The performance and the plasma created by a pulsed magnetoplasmadynamic thruster for small satellite application is studied to understand better the ablation and plasma propagation processes occurring during the short-time discharge. The results can be applied to improve the quality of the thruster in terms of efficiency, and to tune the propulsion system to the needs required by the satellite mission. Therefore, plasma measurements with a high-speed camera and induction probes, and performance measurements of mass bit and impulse bit were conducted. Values for current sheet propagation speed, mean exhaust velocity and thrust efficiency were derived from these experimental data. A maximum in current sheet propagation was found by the high-speed camera measurements for a medium energy input and confirmed by the induction probes. A quasilinear tendency between the mass bit and the energy input, the current action integral respectively, was found, as well as a linear tendency between the created impulse and the discharge energy. The highest mean exhaust velocity and thrust efficiency was found for the highest energy input.

A Maxwell formulation for the equations of a plasma

by Joel Thompson

Co-authored with Trevor M. Moeller
Published in Physics of Plasmas (AIP Journals), January, 2012.
Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

In light of the analogy between the structure of electrodynamics and fluid dynamics, the fluid equations of motion may... more In light of the analogy between the structure of electrodynamics and fluid dynamics, the fluid equations of motion may be reformulated as a set of Maxwell equations. This analogy has been explored in the literature for incompressible turbulent flow and compressible flow but has not been widely explored in relation to plasmas. This letter introduces the analogous fluid Maxwell equations and formulates a set of Maxwell equations for a plasma in terms of the species canonical vorticity and its cross product with the species velocity. The form of the source terms is presented and the magnetohydrodynamic (MHD) limit restores the typical variety of MHD waves.

Identification of Kinetic Alfven Wave Turbulence in the Solar Wind

by Christopher Chen

C. S. Salem, G. G. Howes, D. Sundkvist, S. D. Bale, C. C. Chaston, C. H. K. Chen, F. S. Mozer
Astrophys. J. Lett. 745 L9 (2012)

Anisotropy in Space Plasma Turbulence: Solar Wind Observations

by Christopher Chen

T. S. Horbury, R. T. Wicks, C. H. K. Chen
Space Sci. Rev. (online first), (2011)

X-ray phase contrast imaging of biological specimens with femtosecond pulses of betatron radiation from a compact laser plasma wakefield accelerator

by Stuart Mangles

S. Kneip, C. McGuffey, F. Dollar, M. S. Bloom, V. Chvykov, G. Kalintchenko, K. Krushelnick, A. Maksimchuk, S. P. D. Mangles, T. Matsuoka, Z. Najmudin, C. A. J. Palmer, J. Schreiber, W. Schumaker, A. G. R. Thomas, and V. Yanovsky

We show that x-rays from a recently demonstrated table top source of bright, ultrafast, coherent synchrotron radiation... more We show that x-rays from a recently demonstrated table top source of bright, ultrafast, coherent synchrotron radiation [Kneip et al., Nat. Phys. 6, 980 (2010)] can be applied to phase contrast imaging of biological specimens. Our scheme is based on focusing a high power short pulse laser in a tenuous gas jet, setting up a plasma wakefield accelerator that accelerates and wiggles electrons analogously to a conventional synchrotron, but on the centimeter rather than tens of meter scale. We use the scheme to record absorption and phase contrast images of a tetra fish, damselfly and yellow jacket, in particular highlighting the contrast enhancement achievable with the simple propagation technique of phase contrast imaging. Coherence and ultrafast pulse duration will allow for the study of various aspects of biomechanics.

Self-injection threshold in self-guided laser wakefield accelerators

by Stuart Mangles

published in Physical Review Special Topics - Accelerators and Beams

A laser pulse traveling through a plasma can excite large amplitude plasma waves that can be used to accelerate... more A laser pulse traveling through a plasma can excite large amplitude plasma waves that can be used to accelerate relativistic electron beams in a very short distance—a technique called laser wakefield acceleration. Many wakefield acceleration experiments rely on the process of wave breaking, or self- injection, to inject electrons into the wave, while other injection techniques rely on operation without self- injection. We present an experimental study into the parameters, including the pulse energy, focal spot quality, and pulse power, that determine whether or not a wakefield accelerator will self-inject. By taking into account the processes of self-focusing and pulse compression we are able to extend a previously described theoretical model, where the minimum bubble size kprb required for trapping is not constant but varies slowly with density and find excellent agreement with this model.

Propagation phases of plasma bullets

by Mehmet Arda Akman

Ignition of a large volume plasma with a plasma jet

by Mehmet Arda Akman

Numeric and analytic study of interplanetary coronal mass ejection and shock evolution: Driving, decoupling, and decaying

by Pedro Corona-Romero

Co-authored with J.A. Gonzalez-Esparza. Journal of Geophysical Research, 116, 2011.

We analyze the heliocentric evolution of fast interplanetary counterparts of coronal mass ejections (ICMEs) and their... more We analyze the heliocentric evolution of fast interplanetary counterparts of coronal mass ejections (ICMEs) and their transient shocks to investigate how and where they decelerate in the interplanetary medium. We employ two one-dimensional hydrodynamic models, analytic and numeric, to study three fast CME events. We focus on the transferring of momentum from the ICME to the shock. The two models show that initially the fast ICME propagates at about a constant speed and drives the shock (driving stage) until it reaches a certain distance from which it decelerates and decouples from the shock (decoupling process). Then the ICME and its shock decelerate (decaying stage). This deceleration depends on the speed difference with respect to the ambient wind and tends to a negligible value when the ICME-shock approaches to the ambient wind speed. The location and duration of these propagation stages depend on the initial CME conditions and the ambient wind characteristics. We present a parametric study to compare the results by the analytic and numeric models, showing the variations of their results as a function of the initial conditions. We perform three study cases to compare the model's predictions with a set of speed measurements of ICME-shock events.

Ambipolar Diffusion and Drift in Computational Weakly-Ionized Plasmadynamics

by Bernard Parent

Modeling of ambipolar diffusion and drift taking place within a weakly-ionized fluid can lead to some convergence... more Modeling of ambipolar diffusion and drift taking place within a weakly-ionized fluid can lead to some convergence difficulties when the ion conservation equation and the electric field potential equation are solved consecutively. A novel formulation of the ion flow rate is proposed here that reduces the computing effort to reach convergence by a factor of 10 or more. It is shown that by recasting the ion flow rate in terms of drift and ambipolar diffusion components, the sensitivity to the electric field is reduced hence alleviating the stiffness of the system of equations and permitting significantly faster convergence. What makes the method particularly appealing is that (i) it yields faster convergence without affecting the accuracy of the converged solution and (ii) it is not restricted to specific discretization or relaxation schemes and can hence be readily implemented in existing flow solvers. Because it is developed in general form ({\it i.e.}\ applicable to a multicomponent plasma in the simultaneous presence of electric current and magnetic and electric fields), the method is notably well-suited to simulate ambipolar diffusion within ionized multi-species flow solvers and is recommended for all flowfields as long as the plasma remains weakly-ionized and quasi-neutral.

On the thermodynamics of IGNITOR plasma

by Andrea Di Vita

The filamentary structure in the accelerating plasma sheath of a plasma focus: a simplified three-dimentional analysis

by Andrea Di Vita

Magnetic fluctuations and kinetic equations in a two-species plasma

by Andrea Di Vita

Published in: Journal of Plasma Physics (1991), 46:423-436

Some properties of the frequency spectrum of magnetic fluctuations in a tokamak two-species plasma aremore Some properties of the frequency spectrum of magnetic fluctuations in a tokamak two-species plasma are
investigated. We start from the nonlinear resistive ballooning kinetic equation. A method based on the
fluctuation-dissipation theorem of thermodynamics is employed. The frequency range |@De|/@>|@*e| is
considered. The dependence of magnetic fluctuations on frequency and various macroscopic parameters is
discussed. The influence of magnetic fluctuations on plasma thermodynamics is investigated.

Thermodynamic Stability of a Tokamak Plasma

by Andrea Di Vita

Interal Report JET Joint Undertaking JET-P(93)21
Co-authored with Marco Brusati
Published in J. Plasma Physics  50, 2, 201 (1993)

Stability of stationary states far from thermodynamic equilibrium  is assessed n tokamak plasmas. Violation of... more Stability of stationary states far from thermodynamic equilibrium  is assessed n tokamak plasmas. Violation of Onsager symmetry relationships is observed.

Reply To Dr. Lazzaro & Minardi's Comment On ‘A Minimum Entropy Production Principle For Ohmic Dissipation: Proof And Application To The Fast Analysis Of Non-Inductive Current Density Radial Profiles At JET

by Andrea Di Vita

Published in: Plasma Phys. Contr. Fus. 38, 7, 1085 (1996)
Co-authored with Marco Brusati

Lazzaro and Minardi have claimed that a mathematical error in an equation invalidates the main result of an earlier... more Lazzaro and Minardi have claimed that a mathematical error in an equation invalidates the main result of an earlier paper. It is now shown that the equation is physically justified and mathematically correct.