Last Updated: 01/30/2023

# NAIRAS

Version: 2.0

The NAIRAS model predicts biologically hazardous radiation exposure to commercial aircrews and passengers from the ever-present galactic cosmic rays and the episodic, transient solar energetic particles.

It provides data-driven, global, real-time predictions of radiation exposure rates from galactic cosmic rays (GCR) and solar energetic particles (SEPs) on a geographic 1 × 1 degree latitude and longitude grid, and from the surface of the Earth to 90 km with a vertical resolution of 1 km. The real-time, global predictions are updated every hour. Deterministic, physics-based models are employed to transport cosmic rays through the heliosphere, Earth's magnetosphere, and the neutral atmosphere (Mertens et al., 2012, 2013). GCR are transported through the heliosphere using a modification of the 2010 Badhwar and O'Neill GCR model (Mertens et al., 2013), denoted H-BON10, while the energy spectra of SEPs are specified in situ outside the magnetosphere using NOAA Geostationary Operational Environmental Satellite (GOES) ion flux measurements (Mertens et al., 2010, 2012). Transport through the magnetosphere is parameterized in terms of effective vertical cutoff rigidity, which is based on charged particle trajectory tracing in a dynamically varying geomagnetic field (Kress et al., 2010; Mertens et al., 2010). Cosmic rays are transported through the neutral atmosphere using the High Charge (Z) and Energy TRaNsport (HZETRN) code (Slaba, Blattnig, & Badavi, 2010; Slaba, Blattnig, Aghara, et al., 2010; Wilson et al., 1991). An initial validation of the NAIRAS model version 1.0 was presented for GCR exposures by Mertens et al. (2013). Recently, NAIRAS was updated to HZETRN2015, which includes pion-initiated electromagnetic cascade processes (Norman et al., 2012; Slaba et al., 2013). In addition, a correction was derived for the primary cosmic ray proton and alpha flux in the H-BON10 model, during solar cycle minimum conditions, based on measurements from the satellite-borne Payload for Antimatter Exploration and Light-nuclei Astrophysics (PAMELA) experiment (Adriani et al., 2013, 2016).

## Inputs

1. ACE (EPAM) and GOES (SEM) data to derive the incident SEP spectral fluence rates (5 min averaged).
2. Geomagnetic cutoff rigidities based on IGRF and TS05 (needs input for these models, realtime Dst, solar wind and IMF from ACE/DSCOVR)
3. Atmospheric depth altitude: NCAR/NCEP pressure vs. geopotential height data (extended by invovling NRLMSIS model)

## Outputs

Radiation exposure rates GCRs and SEPs on a geographic 1 × 1 degree latitude and longitude grid, and from the surface of the Earth to 90 km with a vertical resolution of 1 km.

Model is time-dependant.

## Domains

• High Latitude Ionosphere / Auroral Region
• Global Ionosphere

## Space Weather Impacts

• Solar energetic particles - SEPs (human exploration, aviation safety, aerospace assets functionality)
• Galactic cosmic rays - GCRs (human exploration, aviation safety, aerospace assets functionality)

## Publication Policy

In addition to any model-specific policy, please refer to the General Publication Policy.