The Pivot Energy of Solar Energetic Particles Affecting the Martian Surface Radiation Environment

Left: SEP spectral intensity at 500 MeV versus spectral index γ of SEP events used in this study. Right: SEP spectra in the range of 100-800 MeV. Black points (left panel) or black lines (right panel) are the power-law spectra of the original 33 events from Kuhl et al. ¨ (2017). Different coloured ranges are the regenerated spectra with each colour representing a set of SEP spectra with the same power-law index γ, but different intensities.

Space radiation is a major risk for humans, especially on long-duration missions to outer space, e.g., a manned mission to Mars.

Galactic cosmic rays (GCR) contribute a predictable radiation background, the main risk is due to the highly variable and currently unpredictable flux of solar energetic particles (SEPs). Such sporadic SEP events may induce acute health effects and are thus considered a critical mission risk for future human exploration of Mars. Therefore, it is of utmost importance to study, model, and predict the surface radiation environment during such events.

It is well known that the deep-space SEP differential energy spectrum at high energies is often given by a power law. We use a measurement-validated particle transport code to show that, for large SEP events with proton energy extending above ~ 500 MeV with a power-law distribution, it is sufficient to measure the SEP flux at a pivot energy of ~ 300 MeV above the Martian atmosphere to predict the dose rate on the Martian surface. In conjunction with a validation by in-situ measurements from the Martian surface, this remarkable simplification and elegant quantification could enable instant predictions of the radiation environment on the surface of Mars upon the onset of large SEP events.

Jingnan Guo, Robert F. Wimmer-Schweingruber, Yuming Wang, Manuel Grande, Daniel Matthiae, Cary Zeitlin, Bent Ehresmann, Donald M. Hassler
(Submitted on 14 Mar 2020)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); High Energy Astrophysical Phenomena (astro-ph.HE)
Journal reference: J. Guo*, R. F. Wimmer-Schweingruber, Y. Wang, et al. (2019). The Pivot Energy of Solar Energetic Particles Affecting the Martian Surface Radiation Environment, The Astrophysical Journal Letters , 883, 1, L12
DOI: 10.3847/2041-8213/ab3ec2
Cite as: arXiv:2003.06603 [astro-ph.EP] (or arXiv:2003.06603v1 [astro-ph.EP] for this version)
Submission history
From: Jingnan Guo Dr.
[v1] Sat, 14 Mar 2020 10:40:09 UTC (410 KB)

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