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UCL Department of Space and Climate Physics

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PhD Projects 2025: Solar Physics

PhD projects in Solar Physics for our STFC studentships 2025 are listed below.

Particle Acceleration and Plasma Dynamics in Solar Eruptions

Primary Supervisor: Dr Daniel Ryan

Solar eruptions are the largest explosions in the solar system. They can release up to 100,000 times the yearly energy output of all humanity in just a few hours. They can damage and disrupt the infrastructures upon which our society now critically depends, including satellites and power grids. But they are also laboratories wherein we can study some of the most fundamental processes of the Universe.

In this PhD you will use observations from the Solar Orbiter satellite mission to examine some of the earliest observable signatures of solar eruptions: acceleration of charged particles and plasma heating.  Solar eruptions are believed to be driven by magnetic reconnection, a process whereby highly stressed magnetic fields in the Sun's atmosphere suddenly release their excess energy, like the snapping of a stretched rubber band.  However, the processes by which this energy is released and transferred to the particles and plasma, and how they initially evolve, remains poorly understood.  This is despite the fact that these processes occur throughout the Universe, including in active galactic nuclei, stellar atmospheres and planetary magnetospheres, including our own.  The Sun is one of the best laboratories in which to study these processes as its the only celestial body where we can image the locations where they occur.

Thanks to its unique viewing perspectives far beyond Earth, Solar Orbiter, in combination with Earth-orbiting telescopes, can now isolate sources of accelerated particles, reconstruct the 3D nature of hot X-ray-emitting plasma, and observe how the brightest EUV-emitting plasma evolves on timescales relevant to the underlying particle acceleration.  In this PhD, you will leverage the new capabilities to shed new light on particle acceleration and plasma heating in solar eruptions.  This will require learning the design and operation of Solar Orbiter's instruments and developing software workflows to process and analyse their observations.  It may also involve working with the European Space Agency and Solar Orbiter's instrument teams to plan new observations that can further enhance your research, and interpreting models/simulations in comparison to your observations. Thus, by undertaking this PhD, you will help to elucidate how solar eruptions occur and evolve.  And by doing so, you will improve our understanding of fundamental processes that occur throughout the Universe, and the phenomena to which we must adapt as a space-dependent civilisation.

Desired Knowledge and Skills

  • Undergraduate or MSc degree in physics, astrophysics, or related area is desirable, but curious and motivated students with other backgrounds will also be considered.
  • Previous experience of data analysis, as well as good writing and presentation skills, are also desirable but not essential.
  • Previous experience with a computer language, especially Python and/or IDL, is desirable, but inexperienced students committed to learning this skill will also be considered.

Understanding Astrophysical Particle Acceleration using the Sun

Primary Supervisor: Dr Hamish Reid

Particle acceleration and transport are fundamental physical processes that occur over a plethora of astrophysical objects including planetary magnetospheres, solar and stellar coronae, accretion disks, gamma ray bursts, neutron stars, and black holes.  Most astrophysical particle acceleration is astronomically far away which makes data scarce, but our close proximity to our Sun makes it a local laboratory that provides a bounty of data.  During solar flares, particle beams are accelerated to near-light speeds, plasma is super-heated to beyond 10 million Kelvin, and periodically huge volumes of mass, known as solar jets and solar storms, are ejected.  Understanding the acceleration and transport of particle beams is an important, modern challenge.  Moreover, the effect of our active Sun on the Earth (known as space weather) can have a direct economic impact though damaging satellites and disrupting radio communications.  However, much is still not known about these accelerated particles.  For example, how much energy goes into accelerating particles during solar flares?  How do they travel through the solar atmosphere and our solar system?  Can the properties of energetic particle beams be used to predict how the dangerous eruptions of solar jets and storms travel through the solar system?

This PhD project will take advantage of ESA's Solar Orbiter (SolO, launched 2020) that is providing revolutionary new remote observations and in situ measurements of these energetic electron beams, associated electromagnetic fields, and properties of the solar wind plasma closer to the Sun than ever before.  During this PhD project you will be working with a large international group that has been cataloguing hundreds of these energetic particle events observed by Solar Orbiter.  We will analyse direct measurements of these events in the solar system at different distances from the Sun to build up a statistical picture of electron energy transport effects.  We will overcome the inherent uncertainty in single-point spacecraft measurements of electron beam energies by comparing with energy estimates from electron X-ray and radio signatures that originate in the atmosphere of the Sun.  Additionally, we will analyse the extreme ultraviolet signature of the jets of hot plasma that can be ejected after particle beams are accelerated and see whether we can predict how fast they will travel and how they will expand through our solar system.  

For the more numerically minded student, the PhD project will involve simulating the propagation of these near-relativistic electron beams by using a high-performance, parallelised code.  By estimating the initial conditions of the electron beams from Solar Orbiter observations, we can model how these beams propagate out from the atmosphere of the Sun, and how they interact with the solar atmosphere to produce plasma waves that result in the radio emission we detect.  We will use Solar Orbiter direct measurements to bound our results and answer questions regarding electron beam energy content and transport effects.  There is scope to build upon and refine the simulation code by adding additional physical terms to more completely replicate the real physical environment of the Sun.  

The student will develop strong skills in data analysis and/or numerical modelling during the PhD that is relevant both for an academic career and in industry.  The student will also develop their presentation and writing skill necessary for producing scientific papers.  UCL helped build Solar Orbiter and consequently the PhD will have significant opportunities to travel to international universities to collaborate with other teams that are directly involved in running the Solar Orbiter instruments, along with presenting findings at international conferences.  

Desired Knowledge and Skills

  • Undergraduate in astrophysics, physics, computer science, or a related degree.
  • A background in data analysis will be helpful but this can be overcome with strong motivation.
  • Alternatively, a background in computational modelling will also be considered.
  • Some background knowledge in plasma physics is desirable but not essential.

Fast Magnetic Reconnection in Solar Flares – Preparing for Solar-C

Primary Supervisor: Prof. Sarah Matthews

The Sun is our closest star, and with space now firmly established as part of our society’s environment, its unique proximity has inescapable consequences for us. While its radiation provides the energy source of our whole ecosystem, our understanding of how the variations in that radiation control, e.g. our climate, still contains huge gaps. As well as the long-term variations in the solar output, the Sun exhibits a cycle of activity the constituents of which are explosive events which release energy. This explosive energy release occurs on a myriad of scales, from nanoflares to huge eruptive flares, which are accompanied by the bulk eruption of plasma and magnetic field known as coronal mass ejections (CMEs) and whose impacts can be seen globally across the Sun and throughout the heliosphere. The most extreme of these events constitute the largest examples of explosive energy release within our solar system, during which upwards of 1026 J of energy is released. Solar flares comprise a key component of space weather, and yet despite their key importance and the extensive range of observations available from space and the ground, several open questions remain.

Magnetic reconnection is the primary process by which energy release occurs in solar flares with current theories predicting that this occurs in a current sheet high in the corona. While there are many observable signatures predicted by our models, observations of the site and details of reconnection process remain a challenge, particularly spectroscopic observations. However, recent advances in modelling and new techniques for indirectly inferring the conditions in the current sheet provide further opportunities for studying this process. 

The project will initially utilise existing spectroscopic data from the Hinode EIS, IRIS, Solar Orbiter EUI, SPICE and STIX instruments, as well as from ground-based telescopes where available to advance our understanding of the magnetic reconnection processes occurring in solar flares. As we move towards Solar Maximum the student will also have the opportunity to propose and acquire new observations The research undertaken will form part of the solar group’s preparatory work for the Solar C EUVST mission currently under development and scheduled for launch in 2028. The student undertaking this project would thus participate both in the international Hinode EIS and Solar C EUVST teams, including attending team meetings and collaborative visits.

Desired Knowledge and Skills

  • Undergraduate or MSc degree in physics, astrophysics, or related area is desirable, but curious and motivated students with other backgrounds will also be considered.
  • Previous experience of data analysis, as well as good writing and presentation skills, are also desirable but not essential.

Spectroscopic studies of coronal mass ejections

Primary Supervisor: Prof. Lucie Green

The Sun's character is determined by its dynamic and evolving magnetic field, which harbours energy that is used to power some of the most violent and energetic events in the Solar System - coronal mass ejections. These ejections expel billion of tonnes of magnetised plasma into the Solar System and understanding the physical processes that lead to these events is a major focus in international solar physics research. This project will utilise existing spectroscopic and imaging data to study the source regions of coronal mass ejections, watching as these regions evolve to become eruptive. Data from the Hinode EIS, Solar Orbiter EUI and SPICE instruments will be used to garner information on plasma heating, plasma motions and plasma composition variation that can be used to probe when and how an eruptive structure is building. Small-scale process (that ultimately lead to large-scale eruptions) can be studied with facilities such as DKIST. There may also be the opportunity to gather some of the first data showing the evolution of the atmospheric magnetic field, as an eruption looms, using DKIST too. The Solar Group at MSSL is continually working on new solar physics missions, and this means that the research findings from this project will form important preparatory work for the Japanese Solar C EUVST mission, that is scheduled for launch in 2028. There is also the opportunity to implement machine learning techniques to study the large amounts of data that are now available and use this approach to progress our physical understanding of solar eruptions.

Desired Knowledge and Skills

  • Undergraduate in astrophysics, plasma physics or physics
  • Strong computational skills