Characterisation and atmospheric impact of pulsating aurora

Abstract:

Pulsating aurora (PsA) is a scene of irregular shapes of weak emission, which quasi-periodically fluctuates between bright and dim states. PsA occurs predominantly in the local magnetic morning sector and during substorm recovery phases. PsA is associated with high-energy electron precipitation from the radiation belt region. As the precipitating electron energies may reach some 100 keV, strong ionisation may be observed down to the bottom of the D region ionosphere. Consequently, chemical changes can be seen in the neutral atmosphere at the mesospheric heights. Because PsA is common, wide-spread and long-lasting, as compared to many other types of aurora, it is important to better determine its atmospheric impact.

A series of studies using ground and space-based observations characterise the occurrence and impact area of PsA, as well as the energy spectrum of the precipitating electrons. We have used auroral camera data as the ground truth for PsA existence, and complemented that information with coherent and incoherent radar measurements as well as spacecraft particle observations. In addition to better knowledge on the PsA occurrence rate, our results indicate high inter-hemispheric occurrence, and an instantaneous spatial extent typically much wider than that of a substorm both in latitude and local time.

In this presentation, we introduce some key findings from the work characterising the PsA precipitation. We further discuss the atmospheric effects of PsA based on recent atmospheric modelling efforts. However, not every PsA event is equally energetic, so the challenge remaining is to distinguish between those with soft precipitation and those with hard precipitation, and to identify the proper precipitation descriptors for the atmospheric modelling.