Mamoru Ishii

WArning System for AVIation Exposure to Solar energetic particles (WASAVIES) is a physics‐based nowcasting system designed to support warning operations for aviation exposure to solar energetic particles (SEPs) by providing near‐real‐time global SEP dose‐rate estimates. On 11 November 2025, ground level enhancement GLE77 occurred and successfully triggered the SEP mode of WASAVIES, demonstrating fully autonomous initiation of global SEP dose‐rate nowcasts during an extreme space‐weather event. The real‐time analysis, however, was partially degraded during parts of the event due to irregular behavior in some neutron monitor (NM) data streams and evolving background conditions. We therefore performed a post‐event reanalysis using a patched version of the operational algorithm to mitigate these issues. Our analysis indicates that GLE77 consisted of multiple peaks and maintained an unusually low rigidity spectral index (as low as 4) for several hours, suggesting that it was the hardest‐spectrum GLE since 2000. The analysis also indicates that the estimated global maximum effective dose rate (including the galactic cosmic‐ray contribution) briefly exceeded the International Civil Aviation Organization Moderate advisory threshold (30 μSv/h) at altitudes of 14 km (∼FL460) and above, but the exceedance was short‐lived (∼10 min) and limited in magnitude and geographic extent. This finding confirms that GLE77 did not warrant major operational responses such as route or altitude changes. Overall, these results validate the operational potential of WASAVIES and identify key upgrades needed to ensure stable, reliable nowcasts for future extreme events.

WASAVIES (WArning System for AVIation Exposure to Solar energetic particles) is a physics-based nowcasting system designed to support warning operations for aviation exposure to solar energetic particles (SEPs) by providing near-real-time global SEP dose-rate estimates. On 11 November 2025, ground level enhancement GLE77 occurred and successfully triggered the SEP mode of WASAVIES, demonstrating fully autonomous initiation of global SEP dose-rate nowcasts during an extreme space-weather event. The real-time analysis, however, was partially degraded during parts of the event due to irregular behavior in some neutron monitor (NM) data streams and evolving background conditions. We therefore performed a post-event reanalysis using a patched version of the operational algorithm to mitigate these issues. Our analysis indicates that GLE77 consisted of multiple peaks and maintained an unusually low rigidity spectral index (as low as 4) for several hours, suggesting that it was the hardest-spectrum GLE since 2000. The analysis also indicates that the estimated global maximum effective dose rate (including the galactic cosmic-ray contribution) briefly exceeded the ICAO Moderate advisory threshold (30 μSv/h) at altitudes of 14 km (~FL460) and above, but the exceedance was short-lived (~10 min) and limited in magnitude and geographic extent. This finding confirms that GLE77 did not warrant major operational responses such as route or altitude changes. Overall, these results validate the operational potential of WASAVIES and identify key upgrades needed to ensure stable, reliable nowcasts for future extreme events.

We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan, and we discussed the social impact of these phenomena during the Project for Solar–Terrestrial Environment Prediction (PSTEP) in 2015–2019. The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth’s surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity supply and aviation are also given. Some topics requiring future research, which were identified during the survey are also described. Graphic Abstract

Japanese space weather research and operation began in 1896 with research on radio propagation. LF, MF, and HF radio communication used to be important before the era of communication satellites; however, they are affected by ionospheric conditions and solar activity. A center for the research and development of radio systems was established at Hiraiso, which is now also a space weather observatory for measuring solar activity, geomagnetic fields, and ionospheric conditions. The need for space weather information initially decreased in the communication satellite age, but since the beginning of the 21st century it has been increasing again with the growing use of positioning satellite systems. The role of Southeast Asian countries in space weather research has become important and the range of activities is also growing. The contribution of these countries to space weather research and operation is expected to grow in future.

Japanese space weather research and operation began in 1896 with research on radio propagation. LF, MF, and HF radio communication used to be important before the era of communication satellites; however, they are affected by ionospheric conditions and solar activity. A center for the research and development of radio systems was established at Hiraiso, which is now also a space weather observatory for measuring solar activity, geomagnetic fields, and ionospheric conditions. The need for space weather information initially decreased in the communication satellite age, but since the beginning of the 21st century it has been increasing again with the growing use of positioning satellite systems. The role of Southeast Asian countries in space weather research has become important and the range of activities is also growing. The contribution of these countries to space weather research and operation is expected to grow in future.