L I Miroshnichenko
Skobeltsyn Institute of Nuclear Physics, Russia
Posters & Accepted Abstracts: J Aeronaut Aerospace Eng
Near-Earth's environment can be considered as a unique place where different space radiation fields are co-existing and can play a significant role in the estimation of radiation risks both for robotic and manned space missions. One cannot exclude the synergetic effects for particular spacecraft orbits as the result of simultaneous impact of the different radiation fields. Modern state of the problems related to Ground Level Enhancements (GLEs) of Solar Cosmic Rays (SCR) is critically analyzed based on available direct and proxy data. We also consider extremely large fluxes on non-relativistic solar energetic particles (SEP). Special attention is paid to recent debate on validity, origin and properties of the events AD775 and AD1859 (Carrington event). We demonstrate that, in spite of existing uncertainties in proton fluences above 30 MeV, all of them are fitted well by a unique distribution function, at least, with present level of solar activity. Extremely large SEP fluxes are shown to obey a probabilistic distribution with a sharp break in the range of large fluences (or low probabilities). The studies of this kind may be extended for the periods with different levels of solar activity in the past and/or in the future. Considering the recent confirmation of super-flares on solar-type stars, this issue merits attention. Dose rates at aircraft altitudes are also demonstrated during the GLE60 (15 April 2001) along two actual flights (computed from the GLE parameters deduced by different groups), as well as ambient dose equivalent during GLE69 (20 January 2005) computed by different groups for three assumed flights. We consider some examples of using of the models to estimate changes of radiation hazard in the interplanetary space for the expected reduction of solar activity during the nearest solar cycles 25-26.
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