Power spectrum of the electron density data during the ICI-2 flight, presented as spatial scales versus time of flight. The rocket payload is traversing a medium of variable plasma flow, so the horizontal separation Δx between two data samples in the plasma frame of reference is Δx = Δt [V_r + V_E × B], where Δt is the time between samples, V_r is the horizontal speed of the rocket payload (around 1 km/s), and V_E × B is the component of E × B plasma drift along the rocket track. This technique has been used to obtain the spectral analysis of the spatial structures in the electron density. This figure demonstrates that 10-m scale structures extend from more intense irregularities at kilometer scale. The figure is adopted from Oksavik et al. (2012).