Example of roll-off frequency estimation from the PSD based on FFT of 5 min of data between 23:22:30 UT and 23:27:30 UT of January 14th. The blue line represents the log-log spectrum, while the red line shows the fitted function following equation (5). The roll-off frequency is indicated by the dashed blue line, while its standard deviation is represented by the light blue box around it. In the gray box, we report the best fit values and their standard deviation for the constant, the slope and the intercept of equation (5).