The Solar Particle Event on 10–13 September 2017: Spectral Reconstruction and Calculation of the Radiation Exposure in Aviation and Space

Abstract

The solar energetic particle event on 10 September 2017 and on the following days was the strongest event in recent years. It was recorded as ground level enhancement 72 by neutron monitor stations on Earth and measured by a number of instruments in space. One aspect of such a space weather event is the potentially increased radiation exposure in aviation and space. Numerical simulations can help estimate the elevated dose rates during such an event; a critical aspect in these simulations is the description of the primary particle spectrum. In this work, we present 1-hr averaged proton spectra during the event derived from Geostationary Operational Environmental Satellite measurements and described by two different analytic functions. The derived proton spectra are used to calculate the radiation exposure in aviation and different space scenarios: low-Earth orbit, interplanetary space, and Mars surface, and the results are discussed in the context of available experimental data. While the results indicate that in most of these scenarios in aviation and space the event was of little significance compared to the total exposure from galactic cosmic radiation, the skin dose in a lightly shielded environment in interplanetary space may have reached about 30% to 60% of the NASA 30-day dose limit.

Assessment of the Radiation Environment at Commercial Jet‐Flight Altitudes During GLE 72 on 10 September 2017 Using Neutron Monitor Data

“…These results related to radiation environment during GLE 72 are compared with other similar estimates (e.g., Copeland et al, 2018;Kataoka et al, 2018;Matthiä et al, 2018). A good agreement, in the order of 10-14%, at altitude of 50 kft with the exposure reported by Copeland et al (2018) is achieved.…”

Solar Cosmic Ray Dose Rate Assessments During GLE 72 Using MIRA and PANDOCA

“…The primary proton spectra used for the calculation of the exposure related to solar energetic particles were derived by fitting of 1‐hr averages of GOES‐13 and GOES‐15 measurements (more details on the procedure can be found in Matthiä et al, ). The GOES EPEAD (above 10 MeV) and HEPAD proton measurements were fitted with a power law and a double power law in rigidity.…”

“…The German Aerospace Center (DLR, Deutsches Zentrum für Luft‐ und Raumfahrt) began the development of its Professional Aviation Dose Calculator (PANDOCA) for the operational dose assessment of aircrew in Germany in 2005. Although its regular application is the assessment of the GCR component, the PANDOCA radiation transport model can also be used to assess solar particle contributions to the radiation field at aviation altitudes using a correspondingly adapted energy spectrum of the impinging particles and to inform aircrew correspondingly (Matthiä et al, , to be published in this issue). The German Aerospace Center was contacted about the impact of GLE 72 on aviation by concerned aircrew members shortly after the event.…”

The Solar Particle Event on 10 September 2017 as observed onboard the International Space Station (ISS)

“…Using the description of the primary proton spectra during the event derived by Matthiä et al (), the dose rates inside the Columbus module have been estimated. For this purpose, a CAD model of the Columbus module on the ISS was used to create a ray‐traced shielding distribution (Lee et al, ; Stoffle et al, ).…”

“…The primary particle spectra during the event are described by Matthiä et al () as 1‐hr averages. In order to derive the corresponding primary spectra along the ISS orbit, the effective vertical cut‐off rigidity ( R C ) was calculated for each measurement point of the DOSTEL instrument from the corresponding ISS position.…”