The Centre for Fusion, Space and Astrophysics invites applications for research studentships funded by STFC and EPSRC tenable from 1st October each year. Other starting dates might also be possible. For general information, see the Physics Department Graduate Admissions Pages and an application form. Applications should be always submitted through the form on the Department of Physics pages. For information on specific research projects, contact any of the CFSA staff concerned or Prof. Valery Nakariakov who coordinates graduate admissions for the group.
Research Opportunities within the Centre
The Centre for Fusion, Space and Astrophysics offers a broad range of research projects in laboratory and astrophysical plasmas. Research at the centre focuses on plasma physics applied to the grand challenges of fusion power, space physics, solar physics, and astrophysics. Our work spans fundamental theory, observation, and the analysis of experimental data, combined with high performance computing.
For projects in the physics of magnetic and inertial fusion plasmas, two supervisors are typically involved: one based at Warwick, and one at leading international fusion research facilities, such as JET and MAST at CCFE Culham in Oxfordshire. CFSA staff have expertise in the theory of laser-plasma interaction physics, and in high energy density plasma physics. Both topics are central to achieving inertial fusion power.
The study of magnetohydrodynamic waves leads to the concept of MHD seismology, a novel technique for the remote measurement of plasma structures. Coronal seismology uses imaging and spectral data from the solar corona from current missions such as Hinode and SDO, and ground-based facilities. MHD wave modes and transient behaviour seen in JET and MAST are also used to probe the plasma within an operating tokamak.
The CFSA also specialises in complex systems approaches to astrophysical and fusion plasmas. The Centre has active collaborations through Warwick Complexity Complex. Intermittent plasma turbulence is studied in the solar wind through missions such as Cluster (on which the Centre has Co-Investigator status), WIND, ULYSSES and ACE which provide in-situ measurements; and also in the context of turbulent transport in fusion experiments, with data from JET and MAST at CCFE Culham.
Such phenomena present some of the key challenges to High Performance Computing, and CFSA develops codes that cover the full range of plasma behaviour found in fusion and in space plasmas. The CFSA has strong links with Warwick's Centre for Scientific Computing.
Research Areas in CFSA
- Prof Tony Arber
* Laser Plasma Interactions
* Solar Plasma Physics
- Dr Anne-Marie Broomhall
* Helioseismology and Asteroseismology
* Solar and stellar magnetic activity
- Prof Sandra Chapman
* Non-linear processes in astrophysical plasmas, shocks, turbulence and wave particle interactions
* Non-linear physics of magnetically confined fusion plasmas
- Prof Richard Dendy
* Magnetically Confined Fusion Plasmas
- Dr Dirk Gericke
* X-Ray Scattering from Solid-Density Plasmas
* Interaction of Slow Ion Beams with Plasmas
- Dr Bogdan Hnat
* Statistical Properties of Fusion Plasma Edge Turbulence
* Passive Scalar Dynamics in MHD Turbulence
- Dr Ben McMillan
* Advanced numerical algorithms for gyrokinetic Particle-in-Cell simulations of Fusion plasmas
* The effects of kinetic electron physics on zonal flows and toroidal momentum transport
- Prof Valery Nakariakov
* MHD Seismology with Fast Magnetoacoustic Wave Trains
* Stellar Coronal Seismology
* Nonlinear MHD Waves in Plasma Structures
- Dr Erwin Verwichte
* Magnetohydrodynamic (MHD) Waves in Magnetically Confined Plasmas
* Magnetohydrodynamic (MHD) Waves in the Solar Corona
Synthetic diagnostics for laser-driven fusion experiments
Experiments in the US and EU are currently trying to assess the feasibility of firing lasers directly at a deuterium-tritium fuel pellet to drive implosion and ultimately initiate fusion. This is all with a long-term goal of developing a laser driven fusion power source. One possible route forward is so called shock ignition. Here the laser power is kept low while the pellet is being compressed, to avoid deleterious plasma instabilities, and then the power is ramped up at the end to drive a final igniting shock. Warwick has a suite of simulation codes for modelling such experiments but these codes have either transport coefficients which are only approximately known or fast kinetic processes which are not directly observable. This project will develop synthetic diagnostics so that the simulations produce output which can be directly compared to the results of experiments. Going further the aim is to use the datasets from experiments in the US and France to see how well these help to constrain the unknowns in the simulations. The more tightly coupled simulation and experimental datasets will help understand more clearly what is happening in experiments and improve our modelling capability for future laser-fusion programmes.
Solar Plasma Physics
The atmosphere of the Sun above the visible surface (photosphere) is divided in several distinct layers that include the chromosphere, transition region and corona. These layers are highly dynamic with exchange of matter and energy. It is still not clear what maintains the atmospheric temperatures against radiative losses – the so-called heating problem. It is believed that waves have an important role in delivering energy from surface convection into the atmosphere, and may also cause cool chromospheric material to be launched up into the corona (resembling observed spicules). Furthermore, waves are seen in structures at all temperatures and play a part in the cooling process of coronal plasma (oscillating rain). In this project, we shall examine the role of waves at the physical interface between hot (coronal) and cool (chromospheric) plasmas. It will involve a combination of theory, observations and numerical simulation. It will use codes developed at Warwick and data from the solar satellites Hinode, IRIS and SDO along with data from the DKIST ground based telescope due to begin operation in 2019. This project will be lead by Dr. Erwin Verwichte with Prof. Arber supervising the numerical aspects of the project.
Helioseismology and Asteroseismology
Helioseismology uses the Sun’s resonant internal acoustic oscillations to probe beneath the visible surface of the Sun and build up profiles of the solar interior. At any one time thousands of oscillations are trapped in different but overlapping regions of the solar interior and their properties are sensitive to conditions in the plasma they travel through. Therefore, by studying the properties of these oscillations, such as their frequency and amplitude, we can infer, for example, the temperature, density and chemical composition of the solar interior. The properties of these oscillations, such as their frequencies, are also sensitive to the presence of internal magnetic fields and so, using helioseismology, we can constrain the structure and evolution of the Sun’s internal magnetic field. This is important since although it is believed that the Sun’s magnetic field is generated by a dynamo in its interior, little is known for certain beyond this. However, the Sun is just one star and we now know that oscillations also exist inside stars other than the Sun. Asteroseismology uses these oscillations to infer properties about other stars, including, but not limited to, their mass, radius, and age. In this project we will examine variations in the Sun’s internal oscillations through the Sun’s activity cycle, which is a consequence of the solar dynamo. We will also look for seismic signatures of magnetic fields in other stars, placing the Sun in a stellar context and determining how typical a star the Sun really is.
Non-linear processes in astrophysical plasmas, shocks, turbulence and wave-particle interactions
Astrophysical plasmas provide us with an exceptional laboratory for the study of non-linear plasma physics. Turbulence is one of the 'grand challenges' in modern physics and the sun's expanding atmosphere, the solar wind, provides a uniquely well diagnosed laboratory for plasma turbulence using in- situ satellite observations. Shock physics can be studied either within the solar system, and at higher energies at supernova remants. Projects are available which focus on large-scale numerical simulation and on the analysis of data.
Non-linear physics of magnetically confined fusion plasmas
Magnetically confined (tokamak) plasmas show highly non-linear collective behaviour such as self organisation to enhanced confinement states and anomalous transport. Projects are available which focus on modelling, large-scale numerical simulation and on the analysis of data.
Data analysis challenges in the real world
Non-linear plasmas, both in the laboratory, and in our solar system and beyond, provide exemplar challenges in the analysis and visualization of large-scale datasets. In this project, ideas developed in plasma physics will be applied more widely, in the analysis of real world data relevant to space weather, to climate change, in neuroscience and in other complex systems. All of these systems have in common that their behaviour is emergent, it is the result of the interactions between many component elements.
Magnetically Confined Fusion Plasmas
A range of PhD projects in fusion plasma physics is available from CFSA in conjunction with the UK fusion research programme at Culham Science Centre in Oxfordshire. The projects span theory, modelling, interpretation, and experiment. Joint supervision for these PhD projects will be provided by Warwick staff and Culham scientists. I lead the Theoretical Physics Group at Culham, and am happy to facilitate links between prospective PhD students and the wider fusion programme. My own research interests reflect those of CFSA; in conjunction with Warwick staff, I have supervised eight PhD students during the past half-dozen years.
X-Ray Scattering from Solid-Density Plasmas
The scattering of light by a sample (Thomson scattering) has proven to be a very effective tool to determine the plasma properties. Since high-density plasmas are opaque for visible light, X-rays must be used to probe the system. The project will deliver theoretical support for the diagnostics of experiments at RAL and other large laser facilities. The main task is to obtain reliable Thomson cross sections. This requires a novel description of strong correlations between the plasma particles and involves numerical simulations and analytical approaches.
Interaction of Slow Ion Beams with Plasmas
Particles Beams are a prominent tool for heating and diagnosing matter with applications to inertial confinement fusion including novel concepts like fast ignition. Fast beams are well understood, but many questions remain open for slow ions. The project will concentrate on the description of the beam ion charge state and the ionization of plasma particles both requiring in-medium atomic physics. This theoretical project will have strong links to experimental groups using traditional accelarators (GSI, Tokio) and laser accelerated ions (LANL, Luli).
Statistical Properties of Fusion Plasma Edge Turbulence
The heat and particle fluxes toward the material wall in an operating tokamak are often bursty and intermittent. Plasma edge turbulence is one of the ingredients of this complex behaviour. Understanding this process, its development and evolution under different operating regimes, is critical for designing of the future fusion reactors. It has been suggested, for example, that the higher confinement mode of the tokamak operation results from the suppression of edge turbulence. Experimental evidence suggests that statistical properties of edge plasmas are universal and scale invariant. The project explores characterisation of edge plasma fluctuations using statistical measures such as scaling exponents and probability density function invariance. The aim of the project is to develop a stochastic model for fluctuations in the observed edge plasma parameters.
Passive Scalar Dynamics in MHD Turbulence
Passive scalar is an element of the fluid, say a contaminant, that has no dynamical effect on the flow. It is simply advected by the velocity field and diffused by molecular processes. In the case of complicated velocity field, such as that observed in turbulence, passive scalar dynamics and its statistical properties can be used to investigate the flow itself. This project will use numerical MHD simulation to study the dynamics and statistical properties of a passive scalar in 2D and 3D plasma flows. The aim of this investigation is to establish some universal features in the behaviour of passive scalars in different dimensions.
Advanced numerical algorithms for gyrokinetic Particle-in-Cell simulations of Fusion plasmas.
The leading tools for simulating the turbulence at the heart of a fusion device are massively parallelised gyrokinetic codes. The 5D grid in gyrokinetic codes can be resolved using a Monte-Carlo type method known as the particle-in-cell approach. Because the PIC method involves an unstructured sampling of phase space, sampling noise exists in moments of the plasma distribution function. To enable the code to examine long timescela collisional physics, a sophisticated technique for reducing this noise, involving coarse-graining, has been partially implemented in the NEMORB code. This project will involve a more complete implementation including marker reloading would be a major step forward for gyrokinetic PIC simulation.
The effects of kinetic electron physics on zonal flows and toroidal momentum transport.
Zonal flows, analogous to the structured flows on the surface of Jupiter, play a key role in Tokamak transport, and can substantially enhance the confinement levels in certain situations. Toroidal flow structures also play a similar key role in confinement as well as in suppressing large scale instabilities which can lead to exposive release of energy. These dynamics have been investigated in depth, but usually under the assumption that the electrons in the plasma are playing a limited supporting role and simply responding adiabatically to the complex ion motion. This cannot be entirely physically justified, but allows much less taxing turbulence computations. State-of-the-art supercomputing and advanced numerical algorithms as found in the NEMORB code now allow the full problem to be attacked; this project aims to investigate how realistic electron physics modifies the turbulent dynamics and plasma flows.
MHD seismology with fast magnetoacoustic wave trains (funded by ERC AdF)
Fast magnetoacoustic wave trains are detected in the solar corona in radio, EUV and visible light bands. The observed trains have a characteristic "crazy tadpole" signature in the wavelet spectra. Theoretically, appearance of such trains is linked with wave dispersion caused by regular or random structuring of the plasma. We shall design and apply the novel plasma diagnostic technique based upon dispersive fast magnetoacoustic wave trains. This approach allows for almost instant diagnostics of the macroscopic parameters of plasmas during one wave transit time, in contrast with the traditional approach based upon the use of resonances, which requires the
observation of at least several wave transit time. The proof-of-principle demonstration of this technique opens up new opportunities for the diagnostics of natural and laboratory plasmas. The project includes theoretical modelling and analysis of data obtained with the spaceborne SDO/AIA instrument and ground-based radioheliographs.
Stellar coronal seismology (funded by ERC AdF)
Quasi-periodic pulsations (QPP) with the periods ranging from a fraction of a second to several tens of minutes are a common feature of solar and stellar flares. Parameters of QPP impose additional constraints on the estimation of physical parameters and revealing basic physical processes operating in stellar atmospheres. The project aims to contribute to the development of stellar coronal seismology: diagnostics of stellar coronae by QPP in flares. It will be reached by the combination of the theoretical investigation of physical mechanisms for the periodic modulation of the integrated light curves generated by solar and stellar flares, and the analysis of data obtained with Kepler, GALEX and RHESSI space missions and ground-based observational facilities.
Nonlinear MHD Waves in Plasma Structures
Astrophysical plasmas are seen to be highly structured in density, temperature, the magnetic field and steady flows. These structures are natural waveguides for magnetohydrodynamic (MHD) waves. Structuring of the medium brings a lot of interesting properties to the waves, including dispersion, mode coupling and enhanced dissipation. In some circumstances, the plasma can act as an active medium, amplifying the waves. The project aims the theoretical study of the interaction of finite amplitude MHD waves with structured plasmas, in particular to the effects of wave self-organisation and interaction and to negative energy wave phenomena.
Magnetohydrodynamic (MHD) Waves in Magnetically Confined Plasmas
A central challenge for developing viable fusion energy via the route of magnetically confined fusion is an understanding of stability and the transport of particles, momentum and energy. Magnetohydrodynamic (MHD) waves play an important role in the redistribution of fast fusion-born ions (alpha-particles) whose energy is required to heat and sustain fusion. MHD waves are driven unstable by fast ions leading to anomalously high diffusion away from the plasma core and could lead to losses that damage the tokamak walls. The project aims to model MHD waves in tokamaks analytically and their interaction with super-Alfvénic fast ions. Spherical tokamaks, and the Mega-Amp Spherical Tokamak (MAST) at the Culham Centre for Fusion Energy (CCFE) in particular with its extensive diagnostic capabilities, are ideally suited for studying MHD waves. We therefore envisage comparison with data from fusion experiments such as MAST, in collaboration with CCFE.
Magnetohydrodynamic (MHD) Waves in the Solar Corona
The last decade space-born observations have confirmed that the corona of the Sun is awash with magnetohydrodynamic (MHD) waves. These waves are important because they are capable of transferring energy and mechanical momentum from the convection zone into the corona and heliosphere. Thus they are connected to the pivotal questions in solar physics of how the corona is heated and how is the solar wind accelerated. But waves also allows us to extract detailed knowledge of physical conditions in the corona through which they travel. This project aims to study these waves through the combination of observational studies using space-born and ground-based observations from satellites such as the Solar Dynamics Observatory, STEREO, Hinode, RHESSI, etc, and theoretical modelling using MHD wave theory. The balance between observation and theoretical work will be tailored towards the student's taste and ability.