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https://doi.org/10.5194/egusphere-2025-5536
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2025-5536
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Preprints
03 Dec 2025
 | 03 Dec 2025
Status: this preprint is open for discussion and under review for Annales Geophysicae (ANGEO).

High temporal resolution photos of SAR arc rays lead to a new interpretation of the physical causes: Wave-particle interactions and energetic electron precipitation

Bruce T. Tsurutani, Gurbax S. Lakhina, Rajkumar Hajra, Richard B. Horne, Masatomi Iizawa, Yasuhito Narita, Ingo von Borstel, Karl-Heinz Glassmeier, Volker Bothmer, Klaus Reinsch, Philipp Schulz, and Sami Solanki

Abstract. High spatial and temporal resolution images of red auroras over Germany during the 10–11 May 2024 magnetic storm have added new information concerning stable auroral red (SAR) arc formation. The high-altitude red aurora displayed brightness streaks/rays, which continued to lower altitude green auroral brightness rays, indicating that energetic electron precipitation along the Earth’s magnetic field lines are causing both auroras. Both the red and green auroras are diffuse in nature, indicating that instability of high-energy ring current particles inside the plasmasphere followed by wave-particle interactions is the most likely cause of the precipitating electrons. The 5577Å diffuse green aurora below the SAR arcs is a new scientific finding. This is named Stable Auroral Green (SAG) arcs. The SAR and SAG arc images were taken during the first and second steps of the 2024 superstorm. They occurred during intense substorms.

How to cite. Tsurutani, B. T., Lakhina, G. S., Hajra, R., Horne, R. B., Iizawa, M., Narita, Y., von Borstel, I., Glassmeier, K.-H., Bothmer, V., Reinsch, K., Schulz, P., and Solanki, S.: High temporal resolution photos of SAR arc rays lead to a new interpretation of the physical causes: Wave-particle interactions and energetic electron precipitation, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-5536, 2025.
Received: 08 Nov 2025 – Discussion started: 03 Dec 2025
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Bruce T. Tsurutani, Gurbax S. Lakhina, Rajkumar Hajra, Richard B. Horne, Masatomi Iizawa, Yasuhito Narita, Ingo von Borstel, Karl-Heinz Glassmeier, Volker Bothmer, Klaus Reinsch, Philipp Schulz, and Sami Solanki

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Bruce T. Tsurutani, Gurbax S. Lakhina, Rajkumar Hajra, Richard B. Horne, Masatomi Iizawa, Yasuhito Narita, Ingo von Borstel, Karl-Heinz Glassmeier, Volker Bothmer, Klaus Reinsch, Philipp Schulz, and Sami Solanki
Bruce T. Tsurutani, Gurbax S. Lakhina, Rajkumar Hajra, Richard B. Horne, Masatomi Iizawa, Yasuhito Narita, Ingo von Borstel, Karl-Heinz Glassmeier, Volker Bothmer, Klaus Reinsch, Philipp Schulz, and Sami Solanki
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Latest update: 03 Dec 2025
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Short summary
During the 10–11 May 2024 geomagnetic storm, the red auroral rays appear at higher altitudes and connect to green rays lower down. The effect is linked to energetic electrons precipitating into the atmosphere during the storm. As the electrons continue downward, they hit oxygen below 200 km altitude and produce green light (5577 Å), named Stable Auroral Green (SAG) arcs. These observations mark the first reported sightings of such detailed, combined features. 
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