Two-Stream Instability
A fundamental electrodynamic plasma instability that occurs when two counter-streaming particle beams or an electron beam injected into a stationary plasma excite growing electrostatic waves.
Governing formula
1 = (ω_pe1² / (ω - k v₁)²) + (ω_pe2² / (ω - k v₂)²)
SI unit
s⁻¹ (Growth Rate Im(ω))
In depth
Kinetic energy from relative beam velocity v₁ - v₂ feeds electrostatic Langmuir wave growth. Space charge bunches reinforce wave electric fields until non-linear wave trapping saturates the growth.
Examples in the real world
Relativistic electron beam injection into fusion plasmas and solar wind beam-plasma interactions.