Variations in ground irradiance at frequencies higher than 0.1 Hz may severely degrade the performance of automatic imaging systems. For this reason measurements and analysis of fast variations in ground irradiance in the auroral region due to variable auroral emissions have been performed. The largest amplitudes and fastest variations are found to occur during the active phase of geomagnetic substorms and during pulsating auroral conditions, respectively. The power spectra of the variations show a rapid decrease toward higher frequencies. Pulsating auroral conditions contain more power at higher frequencies than do the active phase. On the average ˜10% of the total power in the spectra is at frequencies higher than 0.3 Hz.
© 1984 Optical Society of America
Hans K. Myrabø and Atle Honne, "Fast variations of ground irradiance in auroral regions," Appl. Opt. 23, 2583-2588 (1984)