Variation of the imaginary part of the frequency (ω^′) for pseudo-body (—) and n = 1 (⋅ ⋅) body mode with respect to dimensionless wave-number, kz₀. We fix the wavenumber at k = 5 × 10⁻⁶ m⁻¹ with the slabwidth varying. For each separate diagram the background flow speed has been taken to be u₀ = 16.0 km s⁻¹ and u₀ = 28.0 km s⁻¹, respectively. Panels a and b correspond to ρ_r = 0.01, while panels c and d to ρ_r = 0.02. All panels a–d use a viscosity coefficient of ν = 10¹⁰ m² s⁻¹. Black lines denote an ionisation degree of μ = 0.5, red and blue lines correspond to μ = 0.75 and μ = 0.95, respectively.