The auroras, whose striking images wind up on calendars and screensavers across the world, occur a few thousand kilometres above Earth. Pulsating auroras are another, less-well-known phenomenon. These blinking patches of light at altitudes of tens of thousands of kilometres occur at high latitudes when energetic magnetospheric electrons precipitate out and excite air molecules. Many researchers had hoped that the phenomenon was describable by an interaction between magnetospheric electrons and electromagnetic waves called whistler-mode chorus waves. Now, Satoshi Kasahara of the University of Tokyo and colleagues have used the ERG (Exploration of energization and Radiation in Geospace) spacecraft, launched in December 2016 equipped with instruments to measure electrons and electromagnetic radiation, together with ground-based observations of the aurora, to confirm the proposed explanation.

Further reading

S Kasahara et al. 2018 Nature 554 337.