Radiation and the International Space Station Recommendations to Reduce Risk (2000) / Chapter Skim
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2 Solar Particle Events and the International Space Station
2 Solar Particle Events and the International Space Station
Pages 24-31
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From page 24... ...
but may also be called solar cosmic ray events, solar proton events, solar energetic particle events, energetic storm particle events, ground-level events, proton showers, or polar cap absorption events. Many of these terms, which are for most purposes synonymous, are still in use in the scientific literature.
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From page 25... ...
At present, the NOAA geostationary operational environmental satellites (GOES) are responsible for supplying real-time measurements of energetic particles to SEC for SPE monitoring, while NOAA's National Geophysics Data Center archives SPE data for research.
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From page 26... ...
Therefore, since cycle 22 produced stronger SPEs than the average of the last four cycles, l9 to 22, Turner and Baker's calculations probably underestimate the SPE impact on ISS construction flights. To quantify for this report an exclusive cycle-22 perspective on the problem, Turner and Kemere5 advanced cycle 22's SPE history forward 10 years to represent cycle 23.
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From page 27... ...
The shock-accelerated SPE particles travel toward and away from the Sun along the interplanetary magnetic field (IMF) threading the solar wind, but a significant fraction are trapped near the propagating shock by wave-particle interactions.6 Thus, once the shock reaches Earth, the energetic proton flux can increase suddenly by as much as two orders of magnitude, making this shock spike the most dangerous portion of the solar particle event itself.
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From page 28... ...
, yielding the highest-dose SPEs and the biggest geomagnetic storms. Several situations can give rise to an SPE without a geomagnetic storm to widen the SPE zones: the IMP can point northward throughout the storm; the shock, CME, or both could miss Earth even though SPE particles reach it; or the SPE might come from a west-limb flare without an associated CME.
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From page 29... ...
A Kp proxy for SPE-zone size can be obtained from an empirical relation that specifies in terms of Kp the angular size of a circle defined by the equatorward edge of the auroral oval, which is a rough indicator of the width of the SPE zones.9 The equatorward edge of the auroral oval delimits the volume of the magnetosphere in direct plasma contact with the magnetotail, a volume into which energetic SPE particles can considerably (though not always completely) penetrate.
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From page 30... ...
2.4 SUMMARY AND RECOMMENDATION CSSP/CSTR finds that a concentrated effort aimed at reducing SPE radiation risk to astronauts during ISS construction is needed. Based on the assumption the best now available that the radiation characteristics of the current solar cycle will resemble those of the last cycle, there is nearly a 100 percent chance that at least 2 out of 43 planned ISS construction flights will overlap a significant SPE and a 50 percent chance that at least 5 flights will overlap such an event.
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From page 31... ...
Simon, eds., Catalog of Solar Particle Events, 1955-1969, D Reidel Publishing Co., 1975; H.E.
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