Astrophysics Consolidated Grant

Lead Research Organisation: University of Leeds
Department Name: Applied Mathematics

Abstract

Many astrophysical phenomena involve complex interactions between magnetic fields and fluid flows, often at parameter values far beyond any terrestrial laboratory experiments. We intend to undertake a systematic programme of research to investigate some of these interactions in several astrophysical objects. We shall utilise a combination of analytical and numerical techniques (including the application of state-of-the-art numerical algorithms optimised for use on massively parallel machines) to gain an understanding of such phenomena. Our unifying philosophy is to investigate the fundamental physical interactions in these astrophysical objects and to use expertise gained in one area in order to make progress in other situations with similar underlying dynamics. In all cases we also intend to connect our theoretical/numerical results with astronomically observable quantities. The specific phenomena that we shall address in this proposal are:

(1) Relativistic jets emanating from active galactic nuclei, and the physics governing instabilities that eventually develop over sufficiently large distances from their origin.
(2) Tidal flows in stars and planets, and how the energy dissipated by them affects the evolution of extra-solar planetary systems and binary stars.
(3) Magnetic and thermal evolution of highly magnetised neutron stars, and how this relates to the bursts and flares observed in such stars.
(4) The atmospheres of extra-solar planets, and how they respond to extremely asymmetric heating from their parent stars.

Planned Impact

The British public has a great deal of interest in astronomy, as evidenced by the more than 200 amateur astronomical societies. We have already been involved in giving talks to such societies, and will expand our impact in this direction. We further intend to describe some of our most interesting results in articles for popular science and astronomy magazines. We believe there is considerable scope for explaining the astrophysical theories believed to be behind some of the astronomical observations.

Regarding more technical items, STFC recognizes three ways of maximizing the impact of its investment for the benefit of the United Kingdom and its people - world-class research, world-class innovation and world-class skills. We believe our work qualifies on all three counts, in terms of the astrophysical research itself, the innovation of fundamentally new numerical methods (which may also be useful in areas outside astrophysics), and the training of Postdocs and PhD students in utilizing high-performance computing skills (which again are enormously useful in many areas outside astrophysics).

Publications

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Description We conducted the first three-dimensional numerical modelling of the evolution of magnetic fields and temperature in the crusts of neutron stars, incorporating the effects that astrophysicists believe to be most important. Previously astrophysicists had considered the underlying physical processes, and were (reasonably) confident that they had correctly identified the most important effects (in particular the Hall effect and Ohmic diffusion for the evolution of the magnetic field, and Ohmic heating and anisotropic diffusion for the temperature). It was therefore possible to formulate equations governing the evolution of these quantities, but before our work nobody had successfully implemented a numerical code to actually solve these equations.

With our new code in place, we were further able to make comparisons with astronomical data, and showed that our numerically computed solutions are in good agreement with X-ray emissions from a number of magnetars (neutron stars with ultra-powerful magnetic fields).
Exploitation Route Neutron star astronomers will be interested to compare their observations against some of our numerically computed models. To properly interpret any astronomical observations, it is always best to have detailed theoretical models of what such astrophysical processes might be expected to look like.
Sectors Education

URL https://eps.leeds.ac.uk/maths-research-innovation/news/article/5670/modelling-temperature-variation-on-distant-stars