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Cited by 62Solar and Space Plasma DynamicsIonosphere and magnetosphere dynamicsAstrophysics and Cosmic Phenomena

Long-term modulation of galactic cosmic radiation and its model for space exploration

Badhwar, G.D., O'Neill, P.M.·1994·Advances in Space Research
DOI 10.1016/0273-1177(94)90537-1
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Abstract

As the human exploration of space has received new attention in the United States, studies find that exposure to space radiation could adversely impact the mission design. Galactic Cosmic Radiation (GCR), with its very wide range of charges and energies, is particularly important for a mission to Mars, because it imposes a stiff mass penalty for spacecraft shielding. Dose equivalent versus shielding thickness calculations, show a rapid initial drop in exposure with thickness, but an asymptotic behavior at a higher shielding thickness. Uncertainties in the radiobiology are largely unknown. For a fixed radiation risk, this leads to large uncertain ties in shielding thickness for small uncertainties in estimated dose. In this paper we investigate the application of steady-state, spherically-symmetric diffusion-convection theory of solar modulation to individual measurements of differential energy spectra from 1954 to 1989 in order to estimate the diffusion coefficient, kappa (r,t), as a function of time. We have correlated the diffusion coefficient to the Climax neutron monitor rates and show that, if the diffusion coefficient can be separated into independent functions of space and time: kappa (-r,t)=K(t)kappa 0 beta P kappa 1(r), where beta is the particle velocity and P the rigidity, then (i) The time dependent quantity 1/K(t), which is proportional to the deceleration potential, phi(r,t), is linearly related to the Climax neutron monitor counting rate. (ii) The coefficients obtained from hydrogen or helium intensity measurements are the same. (iii) There are different correlation functions for odd and even solar cycles. (iv) The correlation function for the Climax neutron monitor counting rate for given time, t, can be used to estimate mean deceleration parameter phi(t) to within +/- 15% with 90% confidence. We have shown that kappa(r,t) determined from hydrogen and/or helium data, can be used to fit the oxygen and iron differential energy spectra with a root mean square error of about +/- 10%, and essentially independent of the particle charge or energy. We have also examined the ion chamber and 14C measurements which allow the analysis to be extended from the year 1906 to 1990. Using this model we have defined reference GCR spectra at solar minimum and solar maximum. These can be used for space exploration studies and provide a quantitative estimate of the error in dose due to changes in GCR intensities.

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Crossref · 10.1016/0273-1177(94)90537-1

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  • The GCR spectrum consists of approximately 87% hydrogen ions, 12% helium ions, and 1%-2% HZE nuclei with charges ranging from Z = 3 to approximately Z = 28.

    “The GCR spectrum consists of approximately 87% hydrogen ions (protons) and 12% helium ions (alpha particles), with the remaining 1%–2% of particles being HZE nuclei with charges ranging from Z = 3 (lithium) to approximately Z = 28 (nickel) [9].”

    From Space Radiation: The number one risk to astronaut health beyond low earth orbit (2014) · cites this paper as [9]

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Authors
Badhwar, G. D., & O'Neill, P. M.
Affiliations
Johnson Space Center (US)
ORCID
O'Neill, P.M.
Venue
Advances in Space Research
Publisher
Elsevier BV
Published
1994-10
Volume
14
Issue
10
Pages
749-757
ISSN
0273-1177 (ISSN-L)
DOI
10.1016/0273-1177(94)90537-1
OpenAlex
W2022437901
Cited by
62
References
55
Citations by year
2025: 2 · 2024: 3 · 2023: 2 · 2022: 2 · 2021: 1 · 2020: 2 · 2019: 1 · 2018: 1 · 2017: 6 · 2016: 3 · 2015: 3 · 2014: 3 · 2013: 2 · 2012: 4
FWCI
2.45
Type
journal article
Language
en
Open access
closed
Licence
Locations
  • Advances in Space Research (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Solar and Space Plasma Dynamics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Ionosphere and magnetosphere dynamics
  • Physical Sciences › Physics and Astronomy › Nuclear and High Energy Physics › Astrophysics and Cosmic Phenomena
Keywords
galactic cosmic rays, solar modulation, convection-diffusion model, diffusion coefficient, differential energy spectra, solar cycle, spacecraft shielding, radiation dose, Mars missions, carbon-14 measurement, ionization chamber measurements
MeSH terms
Carbon Radioisotopes, Cosmic Radiation, Energy Transfer, Helium, Ions, Iron, Mathematics, Models, Theoretical, Neutrons, Nuclear Physics, Space Flight, Time Factors, Solar Activity

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