Propagation of solar neutrons through the atmosphere of the Earth

Abstract

The propa•ga•tion of sola•r neutrons through the a•tmosphere of the E•rth h•s been cMcul•ted by • Monte C•rlo method using • nuclear interaction model which c•n reproduce the existing da•t• obtained by •ccelera•tor experiments. With this calcula•tion, it h•s been found tha•t the ela•stic scattering process plays •n importamt role in the propagation of solar neutrons in the •tmosphere •t •n incident energy below ,,• 200 MeV. By a•pplying this c•lcula•tion to the amalysis of a• solar neutron event observed •t Mount Norikur• Cosmic Racy Observa•tory on June 4, 1991, it is possible to interpret the event a•s 7 ra•ys amd neutrons halving been produced impulsively a•t the time of the sola•r fl•re. The event observed Jungfra•ujoch on June 3, 1982 c•n be expladned simila•rly.

Numerical simulation and analytical description of solar neutron transport in the Earth's atmosphere

“…Our results show that: 1) The result of Shibata [1993] with respect to the expected solar neutron flux for inclined arrival of neutrons must be corrected, and 2) The "refraction" effect of solar neutrons suggested by Smart et al [1995] and referred to by Debrunner et al [1993] as "lateral spreading" exists but is not constant; it depends on the variables 0o and h. The causes of this effect are also different from those assumed by Smart et al…”

The World Neutron Monitor Network as a tool for the study of solar neutrons

“…4 that in the energy range below 300 MeV there is great difference between the normalised values as well as between shapes of the sensitivity S n (e.g. Shibata, 1994). It is well known that the integral efficiency of the IGY monitor for solar neutrons is an order of magnitude lower than that of the NM64 monitor (Hatton, 1971).…”

“…There exist several calculations of the sensitivity of NM for solar neutrons, S n , (Debrunner et al, 1983(Debrunner et al, , 1989(Debrunner et al, , 1990Chupp et al, 1987;Efimov and Terekhov, 1988;Gueglenko et al, 1990a;Shibata 1994). The results of the calculations differ significantly from each other.…”

“…For instance, Fig. 4 shows the results of calculations of monitor sensitivity for the actual observational conditions of the 3 June 1982 SNE carried out by Debrunner et al (1983Debrunner et al ( , 1989Debrunner et al ( , 1990, Chupp et al, (1987) and Shibata (1994) for Jungfraujoch (18IGY) and Lomnický Stit (8NM64) monitors, and Efimov and Terekhov for Lomnický Stit NM (Efimov and Terekhov, 1988;Gueglenko et al, 1990a). Hereafter, we denote the corresponding sensitivities as IGY-D and IGY-Sh as well as NM64-D, NM64-Sh and NM64-E, respectively.…”

“…Neither of the calculated curves crosses the 6 area while both lines cross the 6 2 area. This could result from either a Shibata (1994) emphasised the importance of detailed knowledge of the sensitivity at a neutron energy < 300 MeV. However, even a considerable change in the shape of the function in this range could result in only slight changes of the spectral index G. The large difference in the values of G mentioned is mainly due to different normalisations of the sensitivity S n E by different groups, but not due to different shapes of the sensitivities in the energy range below 300 MeV.…”