Prof Philippa Browning - postgraduate opportunities
Solar coronal heating by reconnection and relaxation events:One long-standing unsolved problem in solar physics is to explain how coronal plasma is heated to temperatures of millions of degrees. An attractive idea is that the underlying physical process is the same as that causing solar flares, and thus the hot corona results from a superposition of many “nanoflare” events. The process of magnetic reconnection underlies such events, and also occurs widely in other astrophysical and laboratory plasmas. A student is required to explore models which predict the occurrence of nanoflares, using a theory which postulates that these are triggered by instabilities of the magnetic field. This will involve studies of ideal stability of coronal field configuration, and developing a monte-carlo type model to calculate the distribution of nanoflare events. Numerical simulations involving 2D and 3D magnetohydrodyamic codes may also be carried out.
Acceleration of charged particles in magnetic reconnection:Magnetic reconnection is difficult to observe directly, but an important observational signature is the acceleration of charged particles, and a student could develop models of the energy spectra and other properties of charged particles in reconnection, comparing these with observational data from the RHESSI satellite. A novel feature of the project will be the study of 3D magnetic reconnection configurations. This is of particular relevance to solar flares, as a significant proportion of the energy release in these events is carried by high energy non-thermal charged particles, whose origin is not well understood.
Modelling of fusion plasmas:A number of projects are available in the field of fusion plasmas, in most cases developing theoretical models to explain and interpret experimental results. Culham Laboratory in Oxfordshire is the UK national fusion laboratory, and is home to the internationally leading MAST spherical tokamak and the JET tokamak projects. A number of possible projects are available working jointly with Culham on plasma modelling. These could include studies of edge plasmas in MAST and modelling fundamental processes such as reconnection and particle acceleration, relevant to astrophysical as well as laboratory plasmas.