Fig. 1

Energy spectrum in the wavenumber–frequency domain for the random sweeping model. Color bar scale shows levels of the spectral energy density in the wavenumber–frequency domain, so the squared fluctuation amplitude divided by the frequency interval and by the wavenumber interval. The fluctuation amplitudes are normalized to the mean field (e.g., magnetic field), the frequencies to the ion cyclotron frequency, and the wavenumber interval to the ion inertial scale. The color bar scale is normalized here, and reads \(E/E_{\omega k}\), where \(E_{\omega k} = B_0^2 V_{\mathrm{A}}/\Omega _{\mathrm{i}}^2\)