O. Yu. Nechaev

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.

Near-Equatorial Electrons as Measured onboard the MirSpace Station

Some results of studying the electrons with energies of tens to hundreds of keV at the low and near- equatorial geomagnetic latitudes by using the instruments Sprut-V and Ryabina-2 onboard the Mirspace station in 1991 are presented. It is found that at L< 1.2 the enhanced electron fluxes are sporadically detected, being localized within three longitudinal intervals, 180° W–0°–15° E, 90°– 120° E, and 160° E–180°–135° W. The most intense electron fluxes are observed at the lower edge of the near-equatorial boundary of the inner radiation belt on longitudes of the South Atlantic Anomaly between 14 and 20 h MLT. The occurrence of electron bursts does not depend on the geomagnetic disturbance level. A hardening of the electron spectra is observed near the geomagnetic equator. At L< 1.1, the more energetic particles are located closer to the geomagnetic equator. The results are compared with the data on the low-frequency waves and fields at low and near-equatorial latitudes obtained by the Ariel-4and San Marco Dsatellites, as well as by the spacecraft and ground-based observations of the thunderstorm global distribution. The thunderstorms are considered as a possible source of electron production near the geomagnetic equator.

Thermal neutrons from the earth’s surface during the upper and lower transits of the moon and the sun on new moon and full moon days

The times of increases in the thermal neutron flux from the earth are compared with the passages of the moon and the sun at the longitudes of the observation sites on July 26, 1991, July 27, 1991, July 12, 1995, July 29, 1996, and July 21, 1997 (the upper and lower transits of the moon and the sun). The results confirm the role of tidal forces in the generation of thermal neutron fluxes from the earth’s surface. The study uses the astronomical annuals of the Russian Academy of Sciences for the corresponding years.

Correlation between the synthetic activity of lymphocytes and the intensity of neutron radiation near the Earth surface

The synthetic activity of lymphocytes from rat and ground squirrel was assessed for correlation with the rate of neutron radiation about the Earth surface. In the periods 1999–2002 for rats and 2002–2003 for ground squirrels, significant positive correlation was obtained with the neutron flux incident on Earth and the overall “terrestrial neutron field” but not with the neutron efflux from Earth. No correlation was observed in 2005–2006 when the solar activity and the variation in neutron count were minimal. It is concluded that low-energy neutrons may be bioeffective in periods of substantial variation in flux intensity.

An experiment to study cosmic ray protons and nuclei in the 1011–1014 eV energy range (the ‘TUS’ project)

Abstract An experiment to study cosmic ray protons and nuclei in the 10 11 –10 14 eV energy range is discussed. The instrument measures the number of particles in a shower, generated by the primary particle in a lead absorber (∼14 cm thick). The instrument consists of two Cherenkov charge detectors, and two plastic scintillators viewed by 4 photo multipliers under a lead absorber (see Fig.1). The geometry factor of the instrument with account for the probability of particle recording is 0.015 m 2 sr. Computer simulations of the instrument operation were made to make sure that the instrument is capable of measuring irregularities in the proton spectrum, which presumably exist at E∼10 12 eV.