Development of Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model

In this paper an overview is given of the development of a new nowcast prediction of air-crew radiation exposure from both background galactic cosmic rays (GCR) and solar energetic particle events (SEP) that may accompany solar storms. The new air-crew radiation exposure model is called the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model. NAIRAS will provide global, data-driven, real-time radiation exposure predictions of biologically harmful radiation at commercial airline altitudes. Observations are utilized from the ground (neutron monitors), from the atmosphere (the NCEP Reanalysis and NCEP Global Forecasting System), and from space (NASA/ACE and NOAA/GOES). Atmospheric observations provide the overhead shielding information and the ground- and space-based observations provide boundary conditions on the incident GCR and SEP particle flux distributions for transport and dosimetry simulations. Exposure rates are calculated using the physics-based HZETRN (High Charge and Energy Transport) code. Recent progress in the model implementation is reported and examples of the model results are shown for a representative high-energy SEP event during the Halloween 2003 superstorm, with emphasis on the high-latitude and polar region. The suppression of the geomagnetic cutoff rigidity during these storm periods and their subsequent influence on atmospheric radiation exposure is characterized.