So far no approximations have been done. To be able to proceed we set V = R ω ω g , where ω ω g = q B / m is the gyro frequency and R is the gyroradius. By dividing by ω g, we get 1 ω ω g T ∂ ∂ f ∂ ∂ t ′ + R L v ′ ⋅ ⋅ ∂ ∂ f ∂ ∂ r ′ + ( E V B + v ′ × × B B ) ⋅ ⋅ ∂ ∂ f ∂ ∂ v ′ = 0