Week 6 - Magnetic fields Flashcards
Why do we care about magnetic fields and not electric fields?
Because the fluid is locally neutral but it moves.
Why are resistive effects generally unimportant?
Because the diffusion time L^2/eta in general is much larger then the dynamical time L/U.
State Alfvén’s theorem
In a fluid with infinite electric conductivity, the magnetic field is frozen into the fluid and has to move along with it.
State Kelvin’s circulation theorem
In a barotropic ideal fluid with conservative body forces, the circulation around a closed curve (which encloses the same fluid elements) moving with the fluid remains constant with time
Where does Parker instability occur?
Where the magnetic field lines don’t curve from gravity.
What is Landau damping?
Damping of longitudinal space charge waves in plasma or a similar environment.
Explain two-stream instability.
It can be induced by an energetic particle stream injected in a plasma, or setting a current along the plasma so different species (ions and electrons) can have different drift velocities. The energy from the particles can lead to plasma wave excitation
What does the word quiescent mean?
Without macroscopic movements
