Observations of GLE 77 from the Ground, On Aircraft and Balloons

Cosmic rays generate an ever-present radiation field in Earth’s atmosphere, right down to the ground. On rare occasions, high energy particles accelerated at the Sun can increase this radiation field, in events known as Ground Level Enhancements (GLEs). November 11^th 2025 saw the strongest GLE in nearly 25 years: GLE 77. The event resulted in the count rate of some sea level neutron monitors exceeding 100% of the pre-event mean. In this contribution, we present a comprehensive set of observations of the event made from the UK and the Netherlands. At ground level, we present data from the Compact Neutron Monitors in Guildford, in the south of the England, and Shetland, off the north coast of Scotland. Dose rate measurements are presented from SAIRA instruments onboard two trans-Atlantic flights during the event. In addition, the data from SAIRA instruments onboard weather balloons, launched from Shetland, Cornwall, and the Netherlands, are presented. Finally, modelling results derived from the MAIRE-S system will be shown briefly.