Ground Level Enhancements (GLE) are more likely to occur when the Sun is very active. The most recent GLE was a maverick. It occurred near solar minimum, but it was a large event by historical standards, with a peak increase exceeding 100% at some stations. This talk reports initial observations and modeling of the GLE of December 13, 2006 based on data returned by the “Spaceship Earth” neutron monitor network. Supported by NSF grant ATM- 0527878, the Thailand Research Fund, and a Post-doctoral Fellowship from Mahidol University.

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 1 (SH), pages 229-232