Pulsating Aurora

Pulsating aurora is generated by high-energetic precipitating electrons, causing blinking patches of light below 110 km, sometimes down to an altitude of 70 km. This broad range of altitudes indicates a large range of precipitating electron energies during a pulsating aurora.  The horizontal size of such an aurora ranges from 10 to 200 km with a pulsation period of a few seconds. Recently, an appreciable number of statistical studies have shown that the pulsating aurora occurrence rate is high and can significantly destroy ozone in the middle atmosphere, revealing the importance of pulsating aurora on the atmospheric chemistry.

Usually, pulsating aurora is treated as one phenomenon; however, different structures with different stability over the sky have been reported. In a paper by Fasil Tesema et al. [2020] newly published in Annales Geophysica entitled “Observations of precipitation energies during different types of pulsating aurora”, they have used electron density data from the EISCAT radar, measurements of cosmic noise absorption from the KAIRA network as well as ASC images to study the energy of precipitating electrons during different pulsating auroral structrues.

In this study, the authors find that the ionization level is different for different pulsating auroral structures. Among the three types of pulsating aurora explained in the paper, amorphous pulsating aurora (see left images on the figure on top) showed a relatively low ionization. Both patchy (right image) and patchy pulsating aurora (middle image) showed deeper ionization, which sometimes reached an altitude of 70 km. Based on the occurrence rate and level of ionization, Tesema et al. [2020] concluded that patchy pulsating aurora is the essential type of pulsating aurora in the middle atmosphere.