Given by Professor Stuart Bale, Professor of Physics at the University of California, Berkeley.
The lecture was introduced by Professor Alex Schekochihin and was followed by a Q&A session.
The solar corona is known to be hot. It is much hotter than the Sun below it, which is presumably the source of this heating. It is thought that the mechanisms of coronal heating involve the magnetic fields generated in the outer, convection layers of the Sun. This superhot plasma then escapes solar gravity and is launched as the 'solar wind.' However, for lack of direct measurements, the physical processes responsible for all of this are not currently known. The NASA Parker Solar Probe (PSP) mission was launched in 2018 into an orbit that will take it deep into the corona to make the first in situ measurements of these plasma dynamics. The Parker Solar Probe is a feat of heroic thermal engineering and in its orbit around the Sun is the fastest ever man-made object. Professor Bale will describe the PSP mission and scientific instrumentation and show some measurements from the first few perihelia at 35.7 solar radii. These measurements reveal an emerging solar wind characterised by smooth radial flow, with highly unstable plasma distributions, punctuated by plasma jets dragging along intense, highly kinked magnetic fields. Whereas the solar wind at 1 au is very different—mixed, homogeneous, and relatively stable. We don't know yet the implications of the new measurements, but simple arguments would suggest that these plasma jets play a role in coronal heating.
Watch the lecture
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.