P. I. Shavrin

Increase of solar cosmic rays on the “MIR” space station in orbit during September–October 1989

Abstract An increase in flux and dose rate on the MIR space station caused by solar cosmic rays (SCR) was registered in September–October 1989. This article contains the measurement results, carried out by the “Lyulin” dosimeter and the “Ryabina” radiometer. It is shown that on 29 September 1989 the event per day averaged dose exceeded the background level ten times, while on a number of orbits the dose rate increased more than 50 times. Time behavior of the integral dose agrees well with the dynamics of SCR fluxes measured on the “GOES-7” satellite. On the basis of the proton flux distribution along the space station trajectory, the proton spectrum shape in the range above 1 GV was estimated. It turned out that exponential law is a good approximation of this spectrum. The characteristic rigidity in this law varies from 0.65 GV in an initial moment to 0.35 GV in an isotropic period of an SCR flux.

Long-term measurements of the neutron flux aboard the “MIR”-type space station

Abstract In order to monitor the radiation environment, radiometric instruments were accomodated aboard the “Mir” and most of the “Salyut” space stations. These instruments registered the neutron flux in the energy range from thermal to several MeV. This paper briefly describes the instrument and contains results of the neutron flux measurements performed during 1975–1980. The results reported here were compared with measurements obtained on board the OGO-6 orbital observatory. Measurement data obtained aboard the Salyut-6 space station allowed determination of the integrated neutron flux distribution (mainly local) in the region of the South Atlantic magnetic anomaly and estimation of the albedo neutron flux on the geomagnetic equator (0.06 ± 0.02 cm -2 s -1 ) and on the 45° and 60° geomagnetic latitude (0.43 ± 0.1 and 0.58 ± 0.15 cm -2 s -1 , respectively). The angular distribution of albedo neutrons is described by the following expression: f ( θ ) = 1 + 0.615 cos 4 θ .

Measurements of neutron fluxes with energies from thermal to several MeV in near-Earth space: SINP results.

Neutron measurement results obtained at SINP MSU since 1970 are presented. These measurements were made using techniques based on neutron moderation and subsequent detection in a Li6I(Eu) crystal or a He3 coronal counter. The measurements were mainly carried out in orbits with inclination of 52 degrees and altitudes of 200-450 km. The spatial and angular distributions of the measured neutron fluxes were studied. The albedo neutron flux was estimated according to the count rate difference for opposite detector orientations towards Earth and away from it. This flux is comparable to the local neutron flux outside the Brazil anomaly region, where local neutrons dominate. Neutron fluxes, generated by solar protons, were detected during a solar flare on June 6, 1991 for the first time. Their spectrum was estimated as a power law with alpha>2.

The connection between solar wind velocity variations and the physical and empirical models for electron fluxes in near-Earth space

Abstract Long duration predictions of energetic electron fluxes in near-Earth space is obtained using calculated models. However the existing calculated models, constructed on the basis of experimental data, usually do not sufficiently take into account the variations of the solar wind velocity. Many experiments on satellites such as “Molnia”, “Prognoz”, “Intercosmos” and “Cosmos” show that the energetic electron flux intensity in magnetosheath, magnetopause and geosynchronous orbits depends on the solar wind velocity. Specifically, a quantitative relation has been established between energetic electron fluxes in the outer radiation belt ( L = 3.5−5) and the solar wind velocity value, and the ratios determining time of energetic electron transfer from the magnetospheric boundaries to ionospheric altitudes. A method for determining the dependence observed in physical and empirical models for energetic electron fluxes in near-Earth cosmic space is suggested.