W. Kent Tobiska

Advances in Atmospheric Radiation Measurements and Modeling Needed to Improve Air Safety

Air safety is tied to the phenomenon of ionizing radiation from space weather, primarily from ngalactic cosmic rays but also from solar energetic particles. A global framework for addressing radiation nissues in this environment has been constructed, but more must be done at international and national levels. nHealth consequences from atmospheric radiation exposure are likely to exist. In addition, severe solar radiation nevents may cause economic consequences in the international aviation community due to exposure limits nbeing reached by some crew members. Impacts from a radiation environment upon avionics fromhigh-energy nparticles and low-energy, thermalized neutrons are now recognized as an area of active interest. A broad ncommunity recognizes that there are a number of mitigation paths that can be taken relative to the human ntissue and avionics exposure risks. These include developing active monitoring and measurement programs as nwell as improving scientific modeling capabilities that can eventually be turned into operations. A number nof roadblocks to risk mitigation still exist, such as effective pilot training programs as well as monitoring, nmeasuring, and regulatorymeasures. An active international effort toward observing theweather of atmospheric nradiation must occur to make progress in mitigating radiation exposure risks. Stakeholders in this process ninclude standard-making bodies, scientific organizations, regulatory organizations, air traffic management nsystems, aircraft owners and operators, pilots and crew, and even the public.

Cosmic Radiation Dose Measurements from the RaD-X Flight Campaign

Abstract The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission obtained measurements for improving the understanding of cosmic radiation transport in the atmosphere and human exposure to this ionizing radiation field in the aircraft environment. The value of dosimetric measurements from the balloon platform is that they can be used to characterize cosmic ray primaries, the ultimate source of aviation radiation exposure. In addition, radiation detectors were flown to assess their potential application to long-term, continuous monitoring of the aircraft radiation environment. The RaD-X balloon was successfully launched from Fort Sumner, New Mexico (34.5°N, 104.2°W) on 25 September 2015. Over 18 hours of flight data were obtained from each of the four different science instruments at altitudes above 20 km. The RaD-X balloon flight was supplemented by contemporaneous aircraft measurements. Flight-averaged dosimetric quantities are reported at seven altitudes to provide benchmark measurements for improving aviation radiation models. The altitude range of the flight data extends from commercial aircraft altitudes to above the Pfotzer maximum where the dosimetric quantities are influenced by cosmic ray primaries. The RaD-X balloon flight observed an absence of the Pfotzer maximum in the measurements of dose equivalent rate.

U.S. Government shutdown degrades aviation radiation monitoring during solar radiation storm

The U.S. Government shutdown from 1 to 17 October 2013 significantly affected U.S. and global aviation radiation monitoring. The closure occurred just as a S2 radiation storm was in progress with an average dose rate of 20 μSv h-1. We estimate that during the radiation event period, one-half million passengers were flying in the affected zone and, of this population, four would have received sufficient dose to contract fatal cancer in their lifetimes. The radiation environment can be treated like any other risk-prone weather event, e.g., rain, snow, icing, clear air turbulence, convective weather, or volcanic ash, and should be made available to flight crews in a timely way across the entire air traffic management system. The shutdown highlighted the need for active operational monitoring of the global radiation environment. Aviation radiation risk mitigation steps are simple and straightforward, i.e., fly at a lower altitude and/or use a more equatorward route. Public tools and media methods are also needed from the space weather scientific and operational communities to provide this information in a timely and accessible manner to the flying public.

Influence of Space Weather on Aircraft Ionizing Radiation Exposure

There is a growing concern for the health and safety of commercial aircrew and passengers due to their exposure to ionizing radiation with high linear energy transfer (LET), particularly at high latitudes. The International Commission of Radiobiological Protection (ICRP), the EPA, and the FAA consider the crews of commercial aircraft as radiation workers. During solar energetic particle (SEP) events, radiation exposure can exceed annual limits, and the number of serious health effects, especially to the unborn child of a pregnant air traveler, is expected to be quite high if precautions are not taken. There is a need for a capability to monitor the real-time radiation levels at commercial airline altitudes in order to: (1) provide a continuous assessment of the ionizing radiation field for tracking individual aircrew exposures levels, for the airlines and the FAA to develop policy and procedure for recommending aircrew radiation exposure limits and exposure mitigation; (2) provide time-critical data during SEP events for airline management and pilots to make decisions that balance the cost to flight path alterations against radiation exposure and health risks to passenger and crew; and (3) provide the airline industry with an archived database of radiation exposure levels for assessing the impact of ionizing radiation on the global air transportation system, especially in view of the current and future exponential increase in the number of polar routes. Currently under development is the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model, which provides a global, data-driven, real-time, radiation dose prediction for archiving and assessing the biologically harmful radiation exposure levels at commercial airline altitudes. The NAIRAS model brings to bear the best available suite of Sun-Earth observations and models for simulating the atmospheric ionizing radiation environment. Observations are utilized from ground (neutron

Reply to comment by Rainer Facius et al. on “U.S. Government shutdown degrades aviation radiation monitoring during solar radiation storm”

The premise of this comment perpetuates an unfortunate trend among some radiation researchers to minimize potential risks to human tissue from low-radiation sources. In fact, this discussion on the risk uncertainties of low-dose radiation further illustrates the need for more measurements and a program of active monitoring, especially when solar eruptive events can substantially elevate the radiation environment. This debate also highlights the context of a bigger problem; i.e., how do we as professionals act with due diligence to take the immense body of knowledge of space weather radiation effects on human tissue and distil it into ideas that regulatory agencies can use to maximize the safety of a population at risk. The focus of our article on radiation risks due to solar energetic particle events starts with our best assessment of risks and is based on the body of scientific knowledge while, at the same time, erring on the side of public safety. The uncertainty inherent in our assessment is accepted and described with this same philosophy in mind.