[Paper Review] Space Radiation exposure calculations during different solar and galactic cosmic ray activities

Pavlos Paschalis, Anastasia Tezari+3 more|arXiv (Cornell University)|Dec 28, 2016

Radiation Therapy and Dosimetry3 citations

TL;DR

This paper presents DYASTIMA-R, a new Monte Carlo simulation tool based on Geant4 that calculates equivalent radiation doses for aviation crews and passengers during different solar activity phases. It models energy deposition from galactic cosmic rays (GCR) and solar particle events (SPEs) at various altitudes and latitudes, showing that neutron contributions dominate equivalent dose during solar minimum, while protons contribute most to total absorbed dose.

ABSTRACT

The primary components of radiation in interplanetary space are galactic cosmic rays (GCR) and solar cosmic radiation (SCR). GCR originates from outside of our Solar System, while SCR consists of low energy solar wind particles that flow constantly from the Sun and the highly energetic solar particle events (SPEs) that originate from magnetically disturbed regions of the Sun, which sporadically emit bursts of energetic charged particles. Exposure to space radiation may place astronauts and aviation crews at significant risk for numerous biological effects resulting from exposure to radiation from a major SPE or combined SPE and GCR. Doses absorbed by tissues vary for different SPEs and model systems have been developed to calculate the radiation doses that could have been received by astronauts during previous SPEs. For this reason a new application DYASTIMA-R which constitutes a successor of the Dynamic Atmospheric Shower Tracking Interactive Model Application (DYASTIMA) is being developed. This new simulation tool will be used for the calculation of the equivalent dose during flights scenario in the lower or higher atmosphere, characterized by different altitudes, different geographic latitudes and different solar and galactic cosmic ray intensity. Results for the calculated energy deposition and equivalent dose are calculated during quiet and disturbed periods of the solar cycles 23 and 24, are presented.

Motivation & Objective

• To develop a new radiation exposure simulation tool capable of modeling space radiation in the atmosphere under varying solar and galactic cosmic ray conditions.
• To assess the biological risk from ionizing radiation during commercial air flights, particularly during solar maximum and minimum phases.
• To quantify the contributions of different particle types (protons, neutrons, photons, electrons) to total absorbed and equivalent dose.
• To integrate the tool with real-time space weather data, including GLE alerts, for operational radiation risk assessment.
• To support aviation safety by enabling scenario-based dose calculations for crews, passengers, and aircraft design under different shielding and flight conditions.

Proposed method

• Uses the Geant4 toolkit for Monte Carlo simulation of cosmic ray showers in the atmosphere and their interaction with matter.
• Employs a water-equivalent cylindrical phantom (1.75 m height, 0.25 m radius) to model human tissue for dose calculation.
• Applies the absorbed dose formula D = dE/dm and the equivalent dose formula H = wR × D, where wR is the radiation weighting factor based on LET.
• Incorporates primary GCR spectra from CREME2009 for solar quiet conditions at solar maximum and minimum.
• Simulates particle transport through atmospheric layers and optional aircraft shielding structures to assess shielding effectiveness.
• Integrates with the A.Ne.Mo.S. neutron monitor and ESA’s GLE Alert system for real-time solar activity input.

Experimental results

Research questions

• RQ1 How does the equivalent radiation dose vary across different altitudes and latitudes during solar cycle 23 and 24?
• RQ2 What is the relative contribution of different particle types (e.g., protons, neutrons, electrons) to the total absorbed and equivalent dose?
• RQ3 How do solar maximum and minimum conditions affect GCR intensity and resulting radiation exposure?
• RQ4 To what extent do solar particle events (SPEs) and ground level enhancements (GLEs) increase radiation dose during flights?
• RQ5 How effective are different shielding configurations in reducing equivalent dose for aircrew and passengers?

Key findings

• The equivalent dose during a 7-hour flight is 0.05 mSv during solar quiet periods, rising to 40 mSv during extreme solar particle events (10^5 particles/cm²/sec).
• Galactic cosmic ray (GCR) exposure peaks at solar minimum and is lowest at solar maximum due to the anti-correlation between GCR intensity and solar activity.
• Protons contribute the most to the total absorbed dose, while neutrons are the primary contributor to the total equivalent dose.
• The radiation weighting factor (wR) for neutrons varies with energy, with values of 2.5+18.2exp(-(log En)²/6) for En < 1 MeV, and higher values for intermediate and high-energy neutrons.
• DYASTIMA-R is designed to support real-time radiation risk assessment by integrating with the ESA’s GLE Alert system and NMDB cosmic ray data.
• The tool enables scenario-based dose calculations for various flight profiles, shielding materials, and solar activity phases, supporting safety planning for civil aviation and space missions.