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Last Updated: 05/26/2022

NAIRAS

Version: 3.0

The NAIRAS model predicts biologically hazardous radiation exposure, and radiation flux quantities for the assessment of microelectronic single event effects, to crew and passengers onboard aircraft and spacecraft from the ever-present galactic cosmic rays, inner radiation belt protons in low-Earth orbit, and the episodic, transient solar energetic particles.

The major update in NAIRAS version 3.0 is the development of a run-on-request (RoR) capability for computing (1) global atmospheric dosimetric quantities and (2) dosimetric quantities and radiation flux quantities along a user-input flight trajectory. In addition, the RoR version of the geomagnetic cutoff rigidity model includes an option to select either the TS05 or the T89 magnetospheric magnetic field model. The default is to use TS05 for dates forward of 1995 and T89 for dates prior to 1995. The user can override the default and select IGRF only, or IGRF plus either TS05 or T89 for the magnetospheric magnetic field component.

For the global atmospheric dosimetric RoR selection, the user inputs the date and time. The model run executes the same version of the code as the real-time NAIRAS model. The dosimetric quantities are calculated on a 1 x 1 latitude/longitude grid and at 1-km increments in barometric altitude from 0-90 km. The output quantities are provided at 1-hour time intervals from the user-input start and end dates. The products provide a global context and situational awareness of the atmospheric radiation environment. The global atmospheric dosimetric output quantities also enable retrospective analysis and verification and validation of the real-time version of the NAIRAS model.

For the flight trajectory RoR selection, the user uploads an ascii trajectory file in a specified format that includes date and time and geolocation (latitude, longitude, altitude). Dosimetric quantities and radiation flux quantities are calculated explicitly at the spatial-temporal points in the user input trajectory file. The output dosimetric products enable direct comparisons between model calculations and onboard dosimeter measurements, and the user can specify the effective shielding depths for which the dosimetric quantities are calculated. The flight trajectory version of the NAIRAS model also includes the GEOFFB inner proton belt model. Thus, the user-input trajectory file can be for an aircraft, high-altitude balloon, or LEO spaceflight trajectory. The flux output products are quantities needed for characterizing single-event effects (SEE). The user can specify effective shielding depths for the radiation flux quantities, separate from the shielding depths for the dosimetric quantities, in order to assess the radiation environment and SEE probabilities of individual onboard microelectronic components. In order to provide linear energy transfer (LET) spectra out to 100 MeV-cm2/mg, the composition of the NAIRAS hybrid-BON10 GCR model was extended to include cosmic ray primary nuclei from hydrogen through uranium.

Inputs

  1. GOES (SEISS) data to derive the incident SEP spectral fluence rates (5 min averaged).
  2. Neutron monitors (Oulu, Lomnicky) for GCR and inner proton belt solar cycle modulation
  3. Wilcox Solar Observatory (WSO) solar polar magnetic field data for GCR solar cycle modulation
  4. ACE(EPAM) and Dst, or Kp, for TS05 and T89 magnetospheric magnetic field models, respectively
  5. F10.7 for inner proton belt solar cycle modulation

Outputs

  1. Global Dosimetric Quantities GCR and SEP dosimetric quantities 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 dosimetric quantities include absorbed dose rate in silicon, absorbed dose rate in tissue, dose equivalent rate, ambient dose equivalent rate, and effective dose rate.
  2. Flight Trajectory Quantities GCR, trapped inner belt proton (TRP) for LEO, and SEP dosimetric and radiation flux quantities at the spatial-temporal points of user-input trajectory file. The dosimetric quantities are the same as described for the RoR global dosimetric output. The radiation flux quantities include differential and integral LET flux and fluence (GCR), and differential and integral proton flux and fluence (TRP/SEP) under different user-specified aluminum equivalent shielding depths.

Model is time-dependant.

Domains

  • Geospace
  • High Latitude Ionosphere / Auroral Region
  • Global Ionosphere
  • Thermosphere
  • Exosphere

Space Weather Impacts

  • Near-earth radiation and plasma environment (aerospace assets functionality)
  • Solar energetic particles - SEPs (human exploration, aviation safety, aerospace assets functionality)
  • Galactic cosmic rays - GCRs (human exploration, aviation safety, aerospace assets functionality)

Publications

Contacts

Publication Policy

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