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Atmospheric ionizing radiation from galactic and solar cosmic rays.

Mertens-CJ; Kress-BT; Wiltberger-M; Tobiska-WK; Grajewski-B; Xu-X
Current topics in ionizing radiation research. Nenoi M, ed., Rijeka, Croatia: InTech, 2012 Mar; :683-738
The NAIRAS (Nowcast of Atmospheric Ionizing Radiation for Aviation Safety) prototype operational model is currently streaming live from the project public website (google NAIRAS). NAIRAS predicts biologically hazardous radiation exposure globally from the surface to 100 km in real-time. The NAIRAS model addresses an important national need with broad societal, public health, and economic benefits. Commercial aircrew are classified by European and international agencies as radiation workers, yet they are the only occupational group exposed to unquantified and undocumented levels of radiation. Furthermore, the current guidelines for maximum public and prenatal exposure can be easily exceeded during a single solar storm event for commercial passengers on intercontinental or polar routes, or by frequent use of these high-latitude routes even during background conditions. The NAIRAS model will provide a new decision support system that currently does not exist, but is essential for providing the commercial aviation industry with data products that will enable airlines to achieve the right balance between minimizing flight cost while at the same time minimizing radiation risk. NAIRAS is a physics-based model that maximizes the use of real-time input data. GCR are transported from outside the heliosphere to 1 AU using real-time measurements of ground-based neutron monitor count rates. The SEP particle spectra are determined in-situ using a combination of NOAA/GOES and NASA/ACE ion flux measurements. Both sources of cosmic rays, galactic and solar, are transported through Earth's magnetosphere using a semi-physics-based geomagnetic shielding model. The geomagnetic shielding model utilizes real-time NASA/ACE solar wind and IMF measurements. The cosmic rays are transported from the magnetosphere through the neutral atmosphere using the NASA LaRC's HZETRN deterministic transport code. The real-time, global atmospheric mass density distribution is obtained from the NOAA Global Forecasting System. Global and flight path radiation exposure visualization and decision data products have been developed, which are available at the NAIRAS website. Future research will focus on new science questions that emerged in the the development NAIRAS prototype operational model (Mertens et al., 2010c). The science questions identified by Mertens et al. (2010c) must be addressed in order to obtain a more reliable and robust operational model of atmospheric radiation exposure. Addressing these science questions require improvements in both space weather modeling and observations. The Automated Radiation Measurements for Aviation Safety (ARMAS) is a new initiative to address the deficiencies in observations needed to improve the reliability and robustness of operational aircraft radiation exposure assessment. The ultimate goal of the ARMAS initiative is to integrate onboard radiation instruments into a global fleet of aircraft so that the radiation measurements can be downlinked in real-time and assimilated into the NAIRAS predictions of radiation exposure. A subsidiary goal of ARMAS is to provide a testbed to evaluate the accuracy and reliability of new generations of smaller, cheaper hardware technologies in measuring the atmospheric ionizing radiation field. The ARMAS initiative enables the NAIRAS model to adopt the successful meteorological paradigm for reliable and robust weather forecast, which is physics-based models combined with real-time data assimilation of meteorological fields. The NAIRAS/ARMAS approach is a space weather version of terrestrial weather forecasts. These efforts will occupy the NAIRAS team for the next decade or more. Other research topics unrelated to biological risk from cosmic rays will also be addressed. Effort will also be directed toward predicting the risk that cosmic rays may pose to the operation of microelectronics instrumentation onboard aircraft, and the potential influence cosmic rays may have on the chemistry and climate of planetary atmospheres.
Radiation-exposure; Aircrews; Ionizing-radiation; Monitoring-systems; Models; Exposure-assessment
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Transportation, Warehousing and Utilities
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Current topics in ionizing radiation research