John Carlos Baez on Nostr: When enough electrons get ripped off the molecules of a gas, it can become so ...
When enough electrons get ripped off the molecules of a gas, it can become so electrically conductive that long-range electric and magnetic fields dominate its behavior. Then you've got PLASMA.
Plasma dominates the world of astrophysics. It spans an enormous range of densities and temperatures, from interstellar space to the Sun's core.
For some reason I never seriously studied plasma until a few weeks ago, when the Parker Solar Probe penetrated the boundary separating the solar wind from the Sun's upper atmosphere - its corona.
Trying to understand this, I started reading about the equations of 'magnetohydrodynamics'. These are a combination of the equations for electromagnetism and the equations describing fluid flow. Not all plasmas are well described by the equations of magnetohydrodynamics - they're approximate - but a bunch can. And they describe a bunch of weird things that plasmas do!
First of all, in these equations the magnetic field is generally more important than the electric field - as the name implies.
Second, when the electrical conductivity of the plasma is very high, the magnetic field tends to get 'frozen in' to the plasma. In other words, you can visualize the magnetic field as a bunch of 'field lines' that move along with the flow of the plasma.
But third, these magnetic field lines have pressure: parallel field lines tend to push each other away. And they have tension: curved field lines tend to straighten out!
The math of this is pretty fascinating. The equations are terribly hard to solve, but beautiful to contemplate.
(1/n)
Plasma dominates the world of astrophysics. It spans an enormous range of densities and temperatures, from interstellar space to the Sun's core.
For some reason I never seriously studied plasma until a few weeks ago, when the Parker Solar Probe penetrated the boundary separating the solar wind from the Sun's upper atmosphere - its corona.
Trying to understand this, I started reading about the equations of 'magnetohydrodynamics'. These are a combination of the equations for electromagnetism and the equations describing fluid flow. Not all plasmas are well described by the equations of magnetohydrodynamics - they're approximate - but a bunch can. And they describe a bunch of weird things that plasmas do!
First of all, in these equations the magnetic field is generally more important than the electric field - as the name implies.
Second, when the electrical conductivity of the plasma is very high, the magnetic field tends to get 'frozen in' to the plasma. In other words, you can visualize the magnetic field as a bunch of 'field lines' that move along with the flow of the plasma.
But third, these magnetic field lines have pressure: parallel field lines tend to push each other away. And they have tension: curved field lines tend to straighten out!
The math of this is pretty fascinating. The equations are terribly hard to solve, but beautiful to contemplate.
(1/n)