Culham Plasma Physics Summer School: Day 3

Day 3

Today was a really interesting day of lectures!

It started off with two sessions on Magnetohydrodynamics (MHD) by Prof Phillipa Browning
MHD is the study of the magnetic properties of electrically conducting fluids.
From Wikipedia: The fundamental concept behind MHD is that magnetic fields can induce currents in a moving conductive fluid, which in turn polarizes the fluid and reciprocally changes the magnetic field itself
In essence, it combines the Navier-Stokes equations of fluid mechanics and Maxwell's equations of electromagnetism to form the ideal MHD equations.

MHD describes large-scale phenomena well, such as the astrophysical phenomena. It also describes the behaviour of liquid metals, like the Earth's core and industrial processes. And it can often give useful information even when the conditions for validity are not strictly satisfied, e.g. tokamaks and the Earth's magnetosphere.

Prof Browning took us through a simple derivation of the MHD equations. Then introduced the magnetic Reynold's number and ideal MHD. She then talked us through Alfven's theorem - which effectively says that in a perfectly-conducting plasma, magnetic field lines are frozen into the plasma. This means that if the bulk of the plasma moves, the field lines must distort and move with it.
An example of this is the sun spinning on its axis:
I found this part pretty cool.

Next up we had a problem class on the plasma kinetics. This one actually went down quite well! You can see Daniel and I working on a problem in the mid-right of the photo below (I'm the pleb in the glasses that needs a haircut).

Finally we had a very interesting lecture from Prof Nick Braithwaite on low-temperature plasmas and their applications. I found this very interesting, in large part because I completely glazed over this entire area because I was so excited by the big flashy buzzwords that go alongside high-temperature plasma research. One of the coolest things that Prof Braithwaite showed us, I thought, was this remotely-controlled plasma experiment!

At the end of the day I went on a run along the river and then called it a day.