Photoionisation
Strömgren sphere
UV photons from OB stars ionise H. Recombination emits H-α 656 nm.
Lyman-α trapped.
MHD Turbulence
Alfvén waves
Magnetic pressure B²/8π. Kolmogorov cascade P(k)∝k⁻⁵/³. Ambipolar
diffusion.
Shock Physics
Rankine-Hugoniot
Mach 5–40 shocks. Rayleigh-Taylor instability. Kelvin-Helmholtz
pillars. SiO maser.
Dust Extinction
A_V ~ 1–30 mag
Silicate & carbonaceous grains. κ_ν ∝ ν^β, β≈2. FIR re-emission.
PAH bands.
Star Formation
Jeans mass M_J
Dense cores collapse. Protostellar jets (v~200 km/s). Herbig-Haro
objects. IMF.