Thesis treble for Dr David Hosking

Wednesday 5 July 2023

Mertonian Dr David Hosking has been awarded another two prizes for his DPhil thesis, ‘The decay of MHD turbulence and the primordial origin of magnetic fields in cosmic voids’. He has been awarded the International Astronomical Union’s Exceptional Inter-Division Prize, an IAU first, as well as the Royal Astronomical Society’s Michael Penston Thesis Prize. Earlier this year, Dr Hosking was awarded the European Physics Society Plasma Physics Division’s PhD Research Award.

Dr Hosking's thesis proposes a theory of how chaotic magnetic fields in astrophysical environments decay when their source of energy is removed. The thesis introduces a new integral invariant, the 'Saffman helicity invariant', to express the conservation of the random magnetic helicity – a topological quantity related to linkages and twists of magnetic field lines – contained in large volumes of turbulence. The theory implies a slower decay of primordial magnetic fields in the early Universe than did previous models, suggesting consistency between the deduced strength of the modern-day relics of those fields with observational constraints on the magnetic fields in cosmic voids. The thesis also explores the role of so-called Saffman-like invariants in forced turbulence and considers the effect that tangled magnetic fields might have on the propagation of energy through their host media.

Dr Hosking studied for his DPhil in Astrophysics at Oxford under the supervision of Professors Alex Schekochihin and Steven Balbus. He now holds a postdoctoral fellowship at Princeton Center for Theoretical Science and a research fellowship at Gonville and Caius College, Cambridge.

‘I am delighted to have received thesis prizes from the IAU and the RAS,’ comments Dr Hosking. ‘I am hugely grateful to my DPhil supervisors Alex Schekochihin and Steven Balbus for all their support and encouragement, and for introducing me to some fascinating astrophysical problems, which have been great fun to puzzle over in their company these past few years.’

Professor Balbus comments: 'David, working virtually independently, has tackled some of the most technically challenging problems in astrophysical plasma theory on the behaviour of chaotic magnetic fields. In a field where there had been very little progress for many years, David’s thesis is both ingenious and far-reaching, and I am sure will have a lasting impact on our understanding of how magnetic fields behave in realistic astrophysical settings.'

Professor Schekochihin concludes: 'Working with David was an absolute joy — and he amply deserves the (impressively ample!) recognition he is getting for his work, which has every prospect of acquiring the status of a textbook treatment of the decay of MHD turbulence. Watching his research career unfold further is something we can all look forward to with great fascination and optimism.'

Read more on the IAU website: https://www.iau.org/news/announcements/detail/ann23019/