Solar System Physics PhD Projects

The following are typical PhD projects offered in Solar System Physics. Specific projects may vary from year to year, and related projects may be offered in consultation with the institute.

For further information please contact us at impacs@aber.ac.uk

 

Small Scale Erosional and Depositional Lunar Surface Processes

Supervisor: Dr Anthony Cook and Professor Manuel Grande

Crater count measurements of the lunar surface imply that the geology is of the order of hundreds to thousands of million years old. However effects have been observed that suggest that there are at local scales minor changes. The first of these are from impacts from kg order mass meteorites that have been detected in the past by Apollo seismometers, and more recently by confirmed observations of impact flashes as seen through Earth-based telescopes. The second surface process observed is the electrostatic charging and subsequent levitation of dust particles as detected from the Apollo LEAM instrument and also from dust clouds horizon glow probably seen from orbit by the Clementine spacecraft and Apollo astronauts. Thirdly it has been speculated that interior trapped gases, including Radon and Argon leak out of the Moon’s surface, occasionally in the form of sudden pressurized releases – the Ina formation is one candidate site of past eruptive out-gassing. The proposed project can be tackled in either of two ways. Firstly a practical approach that would look for evidence of localized changes over the Moon’s entire surface of 38 million square kilometres by comparing automatically 1960/70’s era high resolution spacecraft photographs with modern era Lunar Reconnaissance (LRO). In order to reduce the search space areas will be targeted for which the locality of impact flash events are known, where surface maturity maps suggest a freshly disturbed soil, and where unusual surface features have been identified using results from a citizen science internet tool called MoonZoo. The second possible approach to the PhD is to construct theoretical models of how dust particles can become charged and levitate above the lunar surface; current models do not explain this phenomenon fully, especially how dust particles can attain altitudes of the order of 100km. The model should include the shielding effects of topography, the solar wind, and passages through the Earth’s magnetotail. The relevance of this PhD to modern space exploration is that it could help to identify and catalogue interesting targets for future surface missions, and predict which parts of the Moon could prove a dust hazard for astronauts and rovers

Martian Glass

 Supervisors: Dr Anthony CookDr Martin Wilding

 This involves the simulation and study of glass on Mars and will utilize the latest state of the art radiometric colour calibration, close range 3D mapping, and glass and crystal centre analysis techniques applied to Mars exploration imagery. Remotely sensed measurements of candidate martian glass will then be compared to Earth-based simulated glass. Candidates should have a 2.1, or above, in a Physics, Geology, or Chemistry related BSc. A good knowledge of programming, or computer modelling, or remote sensing, would be advantageous.

Space Weather - Disturbances in the solar system

Supervisors:  Professor Manuel Grande

Solar eruptive events - flares and coronal mass ejections - are the most energetic events in the solar system and can have significant effects on Earth, disrupting communications and giving rise to aurora. As yet there are no very good models for understanding the ‘geoeffectiveness’ of these events when they interact with the terrestrial magnetosphere. Establishing the processes by which solar wind disturbances drive radiation belt and ring current dynamics is a key challenge in understanding energy transfer from the Sun to the Earth. While it is accepted that the reconnection-convection-substorm cycle is the most important energy exchange process, the mechanisms of this cycle which determine the impact of the solar wind on the terrestrial environment are still poorly understood. The magnetosphere can be a hostile environment, which may interrupt and degrade communications satellites. Understanding the underlying physical processes is essential both scientifically and for making predictions which can help protect our in situ space systems. We will use data from the recently launched NASA Radiation Belt Storm Probes (Van Allen) mission to investigate substorm and storm dynamics.

Global Maps of Lunar Elemental Abundances

Supervisor: Professor Manuel Grande

The C1XS X-ray spectrometer on the Indian Chandrayaan Lunar Mission, launched in late 2008 provided a hitherto unavailable set of measurements of the surface abundances of Lunar rock forming elements. The data set was excellent, but of limited volume due to the unprecedentedly low activity in the current solar cycle. Aberystwyth as PI institute plays a leading role in data analysis. The first requirement is for global maps form the basis of all subsequent scientific analysis, which. We now need to cross reference these with other lunar data sets, for example from the gamma ray spectrometer. Key questions involve the distribution of Magnesium as a diagnostic of Lunar magma ocean formation, and the investigation of impact basin floor composition as a probe of deeper Lunar composition. The potential for remote sensing of other constituents such as Sodium and Aluminium can also open new areas. It is envisaged that a studentship dedicated to work on production and interpretation of these maps will provide a unique training and for a basis for a career both in space exploration and in Lunar and Planetary science, both areas where the UK offers expanding prospects.

Oxygen and Helium in the Terrestrial Magnetosphere

Supervisor: Professor Manuel Grande

The plasmasphere is the cold (~1eV), ionised region of the upper atmosphere. It co-rotates with the Earth on the closed magnetic field, but is strongly coupled to the solar wind as well as the ionosphere. Its physical parameters (such as size, shape, density distribution, temperature, etc.) are subject to solar effects, via electromagnetic storms and substorms. During enhanced magnetic activity, the size of the plasmasphere reduces significantly, as the outer flux tubes are eroded away to the dayside merging region. After the activity subsides, refilling of depleted flux tubes via the ionosphere, of which the upper extension at mid and low latitudes is the plasmasphere, leads to an increase of the plasmaspheric size.

This project will investigate the sources and sinks of energetic particles in the terrestrial magnetosphere, particularly in the tail, ring current and radiation belts, and cusp, using data from Cluster, Polar CRRES and DoubleStar, augmenting in situ composition measurements with remote sensing measurements using IMAGE. There is still much work to be done in unravelling the stormtime composition history, and how it persists and is modified in quiet times. In fact, the life-cycle of oxygen and helium in the terrestrial magnetosphere has never been fully explained. Helium enters the magnetosphere either singly charged from the ionosphere, possibly via plasmasphere refilling and subsequent erosion and energisation, or doubly charged from the solar wind, while charge exchange from double to single can take place for stably trapped ions. This project will follow on from current work to produce a global picture of oxygen and helium dynamics in storm and quiet times for different parts of the solar cycle.

Jupiter, Ganymede and Europa

Supervisor: Professor Manuel Grande and Dr Tom Knight

The group at Aberystwyth have recently become major partners in the consortium building the particle environment package (PEP) for JUICE, the new ESA flagship mission to the Jupiter magnetosphere and its icy moons. Modelling radiation effects on the instruments, which is the responsibility of the Aberystwyth team, is crucial due to the harsh radiation environment at Jupiter. The plasma package measures positive and negative ions, electrons, neutral gas, and energetic neutral atoms from thermal to relativistic energies with full 3D coverage. It combines in-situ measurements with remote sensing using energetic neutral atoms to explore domains of the Jovian magnetosphere not directly sampled by JUICE. The science goals are especially targeted at understanding the corotating plasma environment of Jupiter, including its extremely efficient generation of relativistic electrons, and understanding the plasma environments of Europa and Ganymede. PEP surpasses the Galileo plasma package in energy range and angular coverage, and carries for the first time a neutral gas mass spectrometer and ENA imagers. These science questions are an excellent fit to the solar system science expertise at Aberystwyth, where we have a strong record for planetary magnetospheres and ionospheres, with an emphasis on energetic particles and plasma composition. Moreover, recent collaborations with the Earth Sciences glaciology group are leading to new insights into the icy surface of Europa, and its interaction with the plasma environment. There are a wide range of PhD possibilities available within the wide range of topics this project opens up.

Oxygen and Helium in the Terrestrial Magnetosphere

Supervisor: Professor Manuel Grande

The plasmasphere is the cold (~1eV), ionised region of the upper atmosphere. It co-rotates with the Earth on the closed magnetic field, but is strongly coupled to the solar wind as well as the ionosphere. Its physical parameters (such as size, shape, density distribution, temperature, etc.) are subject to solar effects, via electromagnetic storms and substorms. During enhanced magnetic activity, the size of the plasmasphere reduces significantly, as the outer flux tubes are eroded away to the dayside merging region. After the activity subsides, refilling of depleted flux tubes via the ionosphere, of which the upper extension at mid and low latitudes is the plasmasphere, leads to an increase of the plasmaspheric size.

This project will investigate the sources and sinks of energetic particles in the terrestrial magnetosphere, particularly in the tail, ring current and radiation belts, and cusp, using data from Cluster, Polar CRRES and DoubleStar, augmenting in situ composition measurements with remote sensing measurements using IMAGE.

There is still much work to be done in unravelling the stormtime composition history, and how it persists and is modified in quiet times. In fact, the life-cycle of oxygen and helium in the terrestrial magnetosphere has never been fully explained. Helium enters the magnetosphere either singly charged from the ionosphere, possibly via plasmasphere refilling and subsequent erosion and energisation, or doubly charged from the solar wind, while charge exchange from double to single can take place for stably trapped ions. This project will follow on from current work to produce a global picture of oxygen and helium dynamics in storm and quiet times for different parts of the solar cycle.

Modelling of planetary magnetospheres, ionspheres and atmospheric erosion at Venus and Mars

Supervisors: Professor Manuel Grande, Dr Balazs Pinter and Dr S. Eleri Pryse

The Earth's atmosphere is a complex system which has undergone a great deal of study and modelling. Recently, efforts have been made to apply this understanding of the Earth's atmosphere to that of other planets. The Venusian atmosphere is unmagnetised and without the magnetospheric cavity to shield the upper atmosphere from the oncoming solar wind, Venus will be subject to comet-like atmosphere erosion processes and solar-wind-induced current systems, which have no terrestrial counterparts.

At Venus, where erosion processes should be highly efficient, we see an extremely dense atmosphere. This is suggestive of refilling of the atmosphere by, for example, volcanism. However there is no evidence as to whether such processes are still active, or the legacy of past episodes.

This project will compare the atmospheres of Earth and Venus by developing existing Earth atmosphere models for use in the Venusian case. The modelling will be strengthened by probing the interaction between Venus and the solar wind using instruments on the Venus Express probe.  There is scope to expand the project to include the atmosphere of Mars in the comparison.

Solar wind acceleration

Supervisors: Dr Xing Li

The solar wind is the supersonically expanding extension into space of the solar atmosphere and is known to be accelerated as it emerges from the Sun's corona. Research at Aberystwyth and elsewhere has established that heavy ions in the solar wind are accelerated more rapidly, and recently evidence has emerged that small-scale turbulent structures are boosted in speed above the background flow. This project combines Aberystwyth's expertise in radio scintillation studies of the solar wind, which is unique in Europe, with computational modelling of solar wind acceleration. Students taking on this project may be required to travel to the high arctic to make observations and to the USA to engage in collaborative work with other modellers

Coronal Heating and Solar Wind Study

Supervisor: Dr Xing Li

The temperature of our solar atmosphere increases from a level about 6000K at photosphere (where our visible light comes from) to about a million K at the dilute corona. The mechanisms responsible for this enormous heating have puzzled solar physicists for decades.

The expansion of the corona into interplanetary space along open magnetic field lines produces the solar wind. However, the acceleration of the wind poses physicists another challenge. Classical solar wind theory cannot account for the properties of the solar wind observed by space probes. It is now understood that the coronal heating and solar wind acceleration may be the two aspects of a single problem. Hence they must be treated on an equal footing.

Observational and theoretical progresses in the past decade concluded that the acceleration of the solar wind primarily occurs in the first few solar radii where coronal heating is continuously going on. However, our knowledge of the gas properties in the first solar radii is still limited. We use SoHO EUV observations to probe the property of the gases in the first few solar radii and our state-of-the-art solar wind models to understand the physical processes.

The grand goal of the project is to understand the coupling of energy and mass between the solar photosphere and the solar wind by combining observations and numerical modelling. A critical issue of the solar wind study will be to develop diagnostic tools to derive solar wind outflow speeds using a Doppler Dimming technique. Such a technique when the Sun is at a minimum phase of activity has already been successfully developed. Doppler dimming technique still requires significant improvements when the solar activity is strong. Our multi-dimensional and multi-component solar wind codes will be used to study the global evolution of the solar wind.

Plasma transport processes in Coronal Mass Ejections (CMEs)

Supervisors: Dr Xing Li 

To understand the physics of CMEs, researchers traditionally model CMEs using the framework of single fluid MHD theory. In this theory, the energy equation is dramatically simplified by adopting a polytropic equation with a small polytropic index. The detailed energy release process which may be the key for understanding the physics of CMEs is largely ignored under such theory. Indeed, observations have shown that the energy release in CMEs is an ongoing process. Oxygen ions have been observed to be heated to hundreds of millions of degrees in CMEs. CMEs have complex magnetic structure and strong current sheets, and plasma waves and turbulence are likely to be important in the current sheets.

The aim of this project is to model CMEs using a multi-fluid approach. Multi-fluid models are essential to describe the evolution of the solar wind properly, since different species have distinct properties. Currently no such 3D model exists. This project will extend our multi-fluid 2.5D solar wind code to 3D, and use this to study the global impact of transient events (such as solar flares and local magnetic reconnections in active regions). This approach will shed light on the role of MHD waves/turbulence in the energy release of CMEs since plasma waves and turbulence may impact different particles in a dramatically different way.

Understanding filament dynamics through linking observation and density models

Supervisor: Dr Huw Morgan

Filaments are knots of tightly-wound and complex magnetic field which can hold cold high density plasma stable in the hot, diffuse solar corona. Many aspects of their structure and dynamics, including their relationship to neighbouring magnetic structure, remain little understood. The Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory has revolutionized our view of the lowest corona by its high spatial resolution and excellent time cadence. In such observations, the highly complex dynamics of filaments are revealed. Interpretation of the dynamics of filaments is extremely difficult with eye alone. Dr. Morgan seeks a highly motivated and independently-minded student to build structural models of filaments, and to simulate the movement of plasma within the constraints of the model structure. Synthetic observations will be made of the simulation, and compared to the true observations. Such work will help reveal the true nature of filaments, and may help in understanding why some filaments erupt into spectacular coronal mass ejections which can affect our life on Earth. The successful candidate will be expected to present results at international conferences and establish collaborations with researchers across the world.

CME structure and evolution in the extended lower corona

Supervisor: Dr Huw Morgan

Coronal Mass Ejections (CMEs) are  spectacular manifestations of the evolution of magnetized plasmas in the extended solar atmosphere, which also have a direct impact on planetary environments, in particular Earth. These phenomena provide clues into the fundamental physical processes that lead magnetic fields to shape solar activity. Exploring their properties will lead to forecasting events on the dynamic Sun that have a significant impact on life and society. We are currently experiencing fast-increasing solar activity, and will in the next two or three years reach a peak in both the energy of individual CMEs and their occurrence rate. New analysis tools developed by Dr. Morgan isolate the signal of CMEs in coronagraph observations. The figure below shows the same CME viewed from different coronagraphs, with background coronal structure removed from the image, and the CME automatically detected using sophisticated new techniques. Dr. Morgan seeks a hard-working, enthusiastic student to use the multi-viewpoint observations of CMEs (as shown in the figure) to calculate the 3D structure and hence the densities of CMEs. This will mean a study of the cross-calibration between the different coronagraphs, the development of appropriate software to reconstruct 3D structure, an inversion to estimate density, and tracking the density structure over time. The ability to automatically estimate 3D CME structure will greatly aid in a large statistical study of CME properties. Other tasks will involve comparing structure and density found using the coronagraph data with values measured using spacecraft at Earth orbit. This work ties in closely with the work of other researchers at Aberystwyth, and is timely given the current availability of multi-spacecraft CME observations and increasing occurrence of CMEs. The successful candidate will be expected to present results at international conferences and establish collaborations with researchers across the world.

Resonant coupling of helioseismic modes into the solar atmosphere

Supervisor: Dr Balazs Pinter

The global solar photospheric oscillations (e.g., the fundamental f- and pressure p-modes with power peaks at around the period of 5 minutes) have proved to be an excellent diagnostic tool for revealing the subtleties of the structure and physical processes of the solar interior. Observations show that the f- and p-modes, which are often referred to as cavity modes, are not completely trapped in the solar interior and can leak into the atmosphere. Hence, observed f- and p-mode oscillations can also provide a novel diagnostic to probe the complex magnetic structure and dynamics of the solar atmosphere. This project will develop a new method of using the solar global oscillations in atmospheric diagnostics by modelling the coupling of the solar interior to the lower and outer solar corona. In particular, questions to be addressed are:

  • How deeply do the f- and p-mode oscillations penetrate into the atmosphere?
  • How efficient is the coupling of the atmospheric magnetic fields to global f- and p-modes?
  • How can observations of solar global modes be used to probe the physics of the solar atmosphere?

The answers to these questions will considerably improve our current understanding of how the apparently distinct layers of the Sun are organically coupled together into one major physical system. New observational techniques, resulting from these theoretical models, will be developed and implemented for local coronal seismology and for the search and analysis of waves and oscillations in various regions of the Sun, from sunspots, through solar tornadoes to solar wind.

Heating and small-scale dynamics in the solar atmosphere

Supervisor: Dr Youra Taroyan

Recent Hinode/EIS observations reveal persistent outflows in active regions near the footpoints of coronal loop structures. In an intensity map of an active region, the overlaying contours indicate regions with significant outflows which are correlated with low intensities and enhanced line widths. In contrast, the same areas become bright and red shifted at lower temperatures. It is likely that heating and cooling lead to variable mass flows along the same magnetic structures. Therefore these observations give us important clues about the nature of the heating mechanism in the corona, something that remains unexplained for many decades.

A detailed analysis of the temporal evolution of the outflows near the footpoints of active region loops will be carried out using data from sit-and-stare Hinode/EIS observations. The analysis will reveal the intermittency of the outflows, their duration. The dependence of the outflows, intensities, and line widths on the temperature will be examined. The obtained results will be used as an input for forward modelling with a C++ code. Synthetic observables will be constructed. The combination of numerical modelling and data analysis will shed light on the unknown heating process. The simulations will be done on the departmental supercomputer and the High Performance Computing Wales facilities.

Theory and Applications of a New MHD Instability

Supervisor: Dr Youra Taroyan

Many physical processes in nature are governed by macroscopic instabilities. Well-known examples are the Rayleigh-Taylor (heavy fluid overlying a light fluid) and the Kelvin-Helmholtz (wind blowing over water) instabilities: small perturbations grow leading to large scale changes in the physical system and transfer of energy. The presence of a magnetic field embedded in a fluid introduces new types of perturbations which may also grow.

The proposed project is dedicated to the theory and applications of a new magneto-hydrodynamic (MHD) instability. The energy extracted from a compressible flow leads to the amplification of arbitrary Alfvenic disturbances. The Alfven instability does not require high flow speeds or shear and is therefore expected to play an important role in magnetic structures of the lower solar atmosphere where upflows and associated nonthermal broadenings are commonly observed with different instruments such as SoHO/SUMER and Hinode/EIS.

The first part of the project is concerned with developing the linear theory of the Alfven instability in magnetic flux tubes: the effects of atmospheric stratification and expansion, the threshold speeds, the spatiotemporal behaviour of the amplified disturbances will be investigated semi-analytically in the linear regime. In the second part, numerical examination of the nonlinear evolution of the instability will be carried out: the energetic and dynamical consequences will be investigated. The amount of energy extracted from the flow and dissipated through the amplification process will be estimated for typical conditions on the Sun. The role of the instability mechanism in solar/stellar coronal heating and wind acceleration will be addressed.