An international team involving scientists from CNRS Terre & Univers and CNRS Physique (LPS) observed an exceptional blue aurora at mid-latitude, revealing unprecedented conditions of interaction between solar particles and the Earth’s atmosphere.
Polar auroras are fascinating for their colors, usually green or red. But an international team involving scientists from CNRS Earth & Universe and CNRS Physics has observed an exceptional phenomenon: a blue aurora visible at mid-latitudes, well south of the regions where they usually appear.
This rare observation testifies to an intense space weather event, capable of extending auroral activity to unusual latitudes. But what makes this event particularly remarkable is its color: blue, very rarely observed in auroras.
Unlike green and red emissions, linked to atmospheric oxygen, blue hues originate primarily from the excitation of nitrogen molecules by energetic particles. These emissions are generally weak and masked, making their detection exceptional.
Through detailed analysis, the scientists show that this optical signature results from specific conditions in the atmosphere and in the flux of incident particles. These results provide a better understanding of the physical mechanisms behind auroras, particularly in extreme situations.
Beyond its spectacular nature, this observation improves our understanding of the interactions between the solar wind, the Earth’s magnetic field, and the atmosphere. It thus contributes to refining space weather models, which are essential for anticipating the effects on satellites, communications, and electrical infrastructure.
CNRS laboratories involved
CNRS Terre & Univers :
- Institut de Recherche en Astrophysique et planétologie (IRAP – OMP)Tutelles : CNRS / CNES / Univiversité de Toulouse
- Institut de planétologie et d’astrophysique de Grenoble (IPAG – OSUG)Tutelles : CNRS / UGA
CNRS Physique :
- Laboratoire dee physique des solides (LPS)
Tutelles : CNRS / Université Paris Saclay
Details
Emmanuel Beaudoin, Jean Lilensten, Guillaume Gronoff, Gaël Cessateur, Léo Bosse, Mathieu Barthélemy, Frédéric Pitout, Cyril Simon Wedlund and Hervé Lamy, J. Space Weather Space Clim. Volume 15, 2025