Diagnostics of the magnetic fields for a monenergetic (upper panels) and a power-law (lower panels) isotropic CR distributions. Left panels: The spatial profiles of the magnetic field components, normalized to the initial magnetic field B₀, at ﹩t\approx 7{\gamma }_{\,\rm{fast}\,}^{-1}﹩. The x-axes are normalized to the wavelengths of the fastest-growing modes (λ_fast = 2π/k_fast ≈ 90d_i). From the shaded zoomed-in part, the dominant wavelengths, almost equal to λ_fast, are prominent. Right panels: Time evolution of helicities Δϕ(k). The positive and negative values signify R-handed NRSI and L-handed RSI, respectively.