16

Search

Monthly medians of the AGW amplitudes in horizontal wind at 90 km height obtained from all four years of the observations. Graphic after Kozlovsky et al., 2025.

Monthly medians of the AGW amplitudes in horizontal wind at 90 km height obtained from all four years of the observations. The visible mid-September–mid-December discrepancy is outlined by the vertical black lines. Graphic after Kozlovsky et al., 2025.

Published: 15 December 2025

International Team report

by Fabio CrameriInternational Team 580

Highlights

From the Teams

Gravitational waves

Meteor

Space Weather

Mesosphere

Meteors and Phenomena at the Boundary between Earth’s Atmosphere and Outer Space

As the year edges toward winter and meteor showers streak across December’s long nights, this ISSI International Team 580 is looking upward: to a region of the atmosphere that is as mysterious as it is beautiful. Their project explores the mesosphere–lower thermosphere (MLT), a thin atmospheric shell at around 80–100 km altitude. Too high for aircraft and balloons, but too low for satellites to provide direct observations. This makes the MLT one of the least explored parts of the Earth’s atmosphere. However, it is a “home” of meteors as they flare into view…

Using a global network of meteor radars, together with satellite observations, the team investigates how this boundary region behaves and how it links the atmosphere to the ionosphere and even the magnetosphere above. Their work spans several interconnected themes:

How meteor trails form and decay, depending on atmospheric conditions and the physical properties of incoming meteoroids.
What we can learn from different meteor streams, from winter favourites like the Geminids and Quadrantids to the well-known summer Perseids and Lyrids.
How atmospheric gravity waves (AGWs) travel upward from the lower atmosphere, influence the ionosphere, and may transform into magnetospheric waves.
How energy and momentum move through the atmosphere–ionosphere–magnetosphere system, especially through the ionospheric dynamo — the electrical “engine” driven by moving air.

These studies bring together atmospheric science, meteor astronomy, plasma physics, and radio science. The team also builds on the earlier ISSI International Team “New features in meteor radar observations and applications for space research” (2017), continuing to push the boundaries of what meteor radars can reveal.

A seasonal surprise: the “fall anomaly”

Recent results show that the behaviour of atmospheric gravity waves at around 90 km and the related ionospheric disturbances at 250–350 km are broadly similar throughout the year — except in autumn! During October–November, the normally active gravity waves near the mesopause drop sharply. This “fall anomaly” coincides with a rapid shift in global atmospheric circulation and a sudden change in the phase of semi-diurnal tides.

Top panel: Seasonal-local time distribution of the relative MSTID median amplitude. White curves roughly indicate times of the sunrise and sunset at 250 km, separating sunlight and dark-sky conditions. Bottom panel: Monthly medians of the AGW amplitudes in horizontal wind at 90 km height obtained from all four years of the observations. The visible mid-September–mid-December discrepancy is outlined by the vertical white lines. Graphic after Kozlovsky et al., 2025.

Top panel: Seasonal-local time distribution of the relative MSTID median amplitude. White curves roughly indicate times of the sunrise and sunset at 250 km, separating sunlight and dark-sky conditions. Bottom panel: Monthly medians of the AGW amplitudes in horizontal wind at 90 km height obtained from all four years of the observations. The visible mid-September–mid-December discrepancy is outlined by the vertical white lines. Graphic after Kozlovsky et al., 2025.

The team found that gravity waves near 90 km can be generated either by turbulence lower down or by electrodynamic forces linked to auroral activity at around 120 km. The latter becomes more important under winter’s long, dark skies. But during autumn nights, something between 90 and 120 km appears to suppress the waves altogether: a new and intriguing phenomenon that calls for deeper study.

(Kozlovsky et al., Surveys in Geophysics, 2025)

Meteor Showers and a Temperature Puzzle

Meteor trails are often used to estimate temperatures near 90 km. But the team discovered that these temperatures are systematically biased during major meteor showers:

Geminids and Quadrantids (winter, asteroid-origin): temperatures appear too low
Perseids and Lyrids (summer, comet-origin): temperatures appear too high

The researchers tried removing meteors from the shower radiant and excluding long-lived, non-specular trails from larger meteoroids. This correction worked well for the Quadrantids, improved the Geminids, but did not fix the offsets for the Perseids or Lyrids.

This led to a bold and exciting hypothesis: during the Perseids and Lyrids, the mesosphere might genuinely warm up. A simplified calculation shows that such a temperature increase is plausible; but confirming it will require further investigation.

(Kozlovsky et al., JGR, 2016)

A Seasonal Note

With winter meteor showers lighting up the December skies, this ISSI team brings a timely reminder: every shooting star is not just a delight for holiday stargazers. It is also a tiny probe of the boundary between our Earth and space. As the Geminids and Quadrantids arrive like nature’s festive fireworks, they help reveal the physics of one of the most elusive regions of our planet’s atmosphere.

The team’s findings highlight just how dynamic ✨ and surprising ✨ this region can be, from unexpected seasonal transitions to unexplained temperature anomalies. More discoveries are sure to come as further international collaboration will surely be sparked to explore the atmospheric frontier.

A Spiral Amongst Thousands

Credits ESA/Webb, NASA & CSA, A. Martel