Characterizing a global aviation radiation environment baseline with
models and measurement databases
Abstract
Two major sources of radiation hazards at commercial aviation altitudes
have been known for decades and those are galactic cosmic rays (GCRs) as
well as solar energetic particles (SEPs). GCRs are produced outside the
solar system in high-energy explosive events and consist mostly of
energetic protons slowly modulated by the strength of the Sun’s
interplanetary magnetic field (IMF). SEPs come from either solar coronal
mass ejections (CMEs) related to flaring events or from IMF shocks. In
the latter case fast CMEs plow through a slower solar wind creating a
shock front to produce energetic protons. Recently, a third radiation
source has been identified that originates from relativistic electron
precipitation (REP) associated with the Van Allen radiation belts and
have been called radiation clouds although a physical perspective is
likely to be flight through a γ-ray beam. This ensemble radiation field
creates safety concerns for aviation. Because of this safety hazard, a
broad community is seeking to i)define the requirements for real-time
monitoring of the charged particle radiation environment to protect the
health and safety of crew and passengers during space weather events;
ii)define the scope and requirements for a real-time reporting system
that conveys situational awareness of the radiation environment to
orbital, suborbital, and commercial aviation users during space weather
events; and iii)develop or improve models for the real-time assessment
of radiation levels at commercial flight altitudes. While benchmarks for
ionizing radiation related to aviation have included characterizing an
occurrence frequency of 1 in 100 years and an intensity level at the
theoretical maximum for radiation events, it is also important to
develop a baseline radiation environment for GCRs, SEPs, and REPs
against which events can be compared. We describe functional, analytical
baselines for describing the ionizing radiation environment for
commercial aviation based on observations and modeling as part of the
NAIRAS, ARMAS, and RADIAN programs.