The 18th Ockham Lecture - 'Magnetised Universe in a Plasma Lab'

Given by Professor Cary Forest, Professor of Physics, University of Wisconsin, Madison, USA, and currently a Visiting Research Fellow at Merton College.

The lecture was introduced by Professor Steven Cowley FRS FREng, CEO of the UK Atomic Energy Authority, Professor of Physics at Imperial College London, and Head of the EURATOM/CCFE Fusion Association, and was followed by a Q&A session.

Watch the lecture

Abstract

Everywhere we look in the Universe, we see turbulent, magnetised plasma. Magnetic fields not only provide a means of observing this plasma (through synchrotron emission detected by radio telescopes) but also play a fundamental role in a number of dramatic phenomena throughout the cosmos, such as accretion onto black holes and generation of radio jets on scales of hundreds of times the size of galaxies, cosmic-ray acceleration, gamma-ray bursts from magnetars and massive solar bursts observed from both our Sun and other stars.

Plasma physics governs these processes. In my lab, I build plasma devices that can mimic, in some ways, astrophysical processes so that we can study them, in situ, as physicists, rather than simply observing. Advances in plasma confinement and heating technology, and diagnostic techniques for measuring the properties of these plasmas (many of which have been developed in the pursuit of nuclear fusion as an energy source), are now being used in the rapidly developing field of laboratory plasma astrophysics.

I will describe three experiments we have built and are now operating. The first addresses the self-generation of magnetic field by plasma flow, a process known as the plasma dynamo. The second is focused on understanding how magnetic fields catalyse accretion of matter onto central objects such as black holes or protostellar/protoplanetary disks. The third investigates the phenomenon of "magnetic reconnection," which allows immense amounts of magnetic energy to be released explosively (as happens in the solar flares on in gamma-ray bursts from magnetars).

The Ockham Lecture series

The Merton College Physics Lecture (the Ockham, or Occam, Lecture, so named in honour of one of the greatest—if unattested—alumni of the College and of his philosophical principle of intellectual discipline) started in 2009 and is held once a term. It is organised by the physics tutors of the College to promote both intellectual curiosity and social cohesion of the Merton Physics community.

Attendance is by invitation: All Merton physicists (and sympathisers!) belonging to the three Common Rooms (JCR, MCR and SCR) are invited, as are the Old Members. Their guests are also accommodated, space permitting.