A statistical study of pulsating aurora

Pulsating aurora is a phenomenon that consists of irregular patches of faint luminosity blinking at different frequencies.

In a statistical study entitled “Occurrence and average behavior of pulsating aurora“, Noora Partamies and co-authors have examined the bulk behavior of auroral pulsations. Their study has been motivated by recent event studies and modeling efforts that conclude that the precipitation energy during pulsating aurora events is high enough to cause significant chemical changes in the mesosphere.

“Usually we are not able to see pulsating aurora with our own eyes”, Partamies explains. She continues, “Pulsating aurora consists of faint luminosity which can be below the observable threshold for the naked eye. The human eye is also not very good at detecting diffuse aurora but, rather, looks for regions of clear contrast”.

To measure the pulsating aurora analyzed in this study, Partamies et al. used data from five all-sky cameras in the Lapland region operated by Finnish Meteorological Institute, as well as magnetometer data from the same stations to allow substorm phase detection.

Dr. Noora Partamies, Associate professor at UNIS, Svalbard

Shown above is figure 3 from the paper showing auroral images of diffuse nonpulsating aurora (00:25 UT) to pulsating arcs (01:10 UT), large elongated pulsating patches (02:12 UT), and small pulsating features (02:54 UT) measured at Kilpisjärvi, Finland.

The results found in this extensive statistical study of pulsating aurora shows that a systematic decrease in the peak emission height of about 8 km takes place at the beginning of the events. This hints for increased precipitation energy, which makes the particles penetrate deeper into the atmosphere. Pulsating aurora is shown to last for hours and often occur on both hemispheres at the same time. ”The fact that auroral pulsations can go on beyond the magnetic disturbances of geomagnetic storms and substorms suggests that the magnetic proxies for energetic particle precipitation do not take into account this type of particle precipitation, although the cumulative effect of pulsating aurora may be important.”

Based on the results found in this study, Partamies and her co-authors plan to next investigate the atmospheric effects of this kind of particle precipitation.