UV radiation from the atmosphere: Results of the MSU “Tatiana” satellite measurements

In the space experiment a near visual UV radiation (NUV) from the Earth atmosphere was measured during the moon month. At moonless local nights the results of previous measurements are confirmed: NUV intensity is in limits of 3 × 107–108 photons/cm2 s sr. At the background of natural NUV light the light from big cities was registered. In a detector FOV (the corresponding diameter of the observed atmosphere area is 250 km) the brightest cities radiate NUV comparable with the natural level. At moon nights the NUV intensity depends on the moon phase, the moon local zenith angle and cloud cover. Monitoring of the average NUV intensity shows that only in 1/4 of the moon month the average intensity is over 109 photons/cm2 s sr. The method of digital oscilloscope was applied for searching and registering the short NUV flashes (from 1 to 10 ms). The trigger system selects the brightest flash in one satellite circulation. In the registered NUV flashes the energy radiating in the atmosphere in 1–10 ms is of the order of 1011–1013 erg. Those energetic flashes are found to be concentrated in the Earth equatorial region.