'Metal clouds': Scientists detect unusual anomaly in Earth’s upper atmosphere caused by solar superstorm

A powerful geomagnetic storm in May 2024 has led to an unexpected and mysterious atmospheric phenomenon: the sudden emergence of metal-rich ionised clouds which are also known as sporadic E layers, in the Earth's upper atmosphere. A study that was published in Geophysical Research Letters by scientists from Kyushu University focusses on these little-understood patches of ionised material that form between 90 and 120 kilometres above sea level.

The research team, led by Professor Huixin Liu, turned its focus to the sporadic E layer, often overlooked in favour of the higher F layer where most ionisation typically occurs. "The sporadic E layer hasn’t been studied very much during geomagnetic storms," said Professor Liu. These clouds are thin, just 1 to 5 kilometers thick, but incredibly dense. These clouds appear suddenly, but vanish just as quickly.

Using data from 37 ground-based ionosondes and COSMIC-2 satellites, the researchers constructed one of the most detailed global maps of sporadic E activity during and after the storm. This study found that the clouds had first appeared in polar regions however, they later on, gradually moved to lower latitudes including Southeast Asia, Australia, and the South Pacific. Hence, this pattern indicates a global atmospheric wave was set in motion by the storm.

The findings of the study challenge the assumption of these sporadic E layers being driven mainly by the local atmospheric processes. Instead, it now suggests large-scale disturbances, especially in neutral winds in the E region, may play a significant role. "We found that sporadic Es formed during the recovery phase of the storm and propagated from high to low latitudes," said Liu.

The sporadic E layer may interfere with radio signals in HF and VHF bands, which are critical for aviation and maritime operations. This research could help improve forecasting models.