V. V. Bogomolov

Peculiarities of intrinsic background in LaBr3: Ce and CeBr3 scintillating crystals

The intrinsic background was measured in LaBr3:Ce and CeBr3 scintillating crystals grown at the Institute of Solid-State Physics of the Russian Academy of Sciences. The measurements were taken in the range of γ-ray energies from 20 keV to ∼5 MeV. Cylindrical samples with dimensions of Ø 1.5 × 1.8 cm for LaBr3:Ce and Ø 0.5 × 1.5 cm for CeBr3 were used. Well-known peculiarities due to the 138La radioactive iso-tope and actinide contaminants were reproduced in the recorded background spectrum of the LaBr3:Ce crystal. The detailed spectrum of the intrinsic background in the CeBr3 crystal was measured for the first time. At energies of >200 keV, the background rate of CeBr3 appeared to be much lower than that of LaBr3:Ce both in the continuum and in the peculiarities associated with the radioactivity of possible contaminants.

Dynamics and Energetics of the Thermal and Nonthermal Components in the Solar Flare of January 20, 2005, Based on Data from Hard Electromagnetic Radiation Detectors Onboard the CORONAS-F Satellite

Based on data from the SONG and SPR-N multichannel hard electromagnetic radiation detectors onboard the CORONAS-F space observatory and the X-ray monitors onboard GOES satellites, we have distinguished the thermal and nonthermal components in the X-ray spectrum of an extreme solar flare on January 20, 2005. In the impulsive flare phase determined from the time of the most efficient electron and proton acceleration, we have obtained parameters of the spectra for both components and their variations in the time interval 06:43–06:54 UT. The spectral index in the energy range 0.2–2 MeV for a single-power-law spectrum of accelerated electrons is shown to have been close to 3.4 for most of the time interval under consideration. We have determined the time dependence of the lower energy cutoff in the energy spectrum of nonthermal photons Eγ0(t) at which the spectral flux densities of the thermal and nonthermal components become equal. The power deposited by accelerated electrons into the flare volume has been estimated using the thick-target model under two assumptions about the boundary energy E0 of the electron spectrum: (i) E0 is determined by Eγ0(t) and (ii) E0 is determined by the characteristic heated plasma energy (≈5kT (t)). The reality of the first assumption is proven by the fact that plasma cooling sets in at a time when the radiative losses begin to prevail over the power deposited by electrons only in this case. Comparison of the total energy deposited by electrons with a boundary energy Eγ0(t) with the thermal energy of the emitting plasma in the time interval under consideration has shown that the total energy deposited by accelerated electrons at the beginning of the impulsive flare phase before 06:47 UT exceeds the thermal plasma energy by a factor of 1.5–2; subsequently, these energies become approximately equal and are ∼(4–5) × 1030 erg under the assumption that the filling factor is 0.5–0.6.

Experiment on the Vernov satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part I: Description of the experiment

The program of physical studies on the Vernov satellite launched on July 8, 2014 into a polar (640 × 830 km) solar-synchronous orbit with an inclination of 98.4° is presented. We described the complex of scientific equipment on this satellite in detail, including multidirectional gamma-ray detectors, electron spectrometers, red and ultra-violet detectors, and wave probes. The experiment on the Vernov satellite is mainly aimed at a comprehensive study of the processes of generation of transient phenomena in the optical and gamma-ray ranges in the Earth’s atmosphere (such as high-altitude breakdown on runaway relativistic electrons), the study of the action on the atmosphere of electrons precipitated from the radiation belts, and low- and high-frequency electromagnetic waves of both space and atmospheric origin.

Electron flux variations at altitudes of 600–800 km in the second half of 2014. preliminary results of an experiment using RELEC equipment onboard the satellite VERNOV

The results of measurements of fluxes and spectra carried out using the RELEC (relativistic electrons) equipment onboard the VERNOV satellite in the second half of 2014 are presented. The VERNOV satellite was launched on July 8, 2014 in a sun-synchronous orbit with an altitude from 640 to 830 km and an inclination of 98.4°. Scientific information from the satellite was first received on July 20, 2014. The comparative analysis of electron fluxes using data from RELEC and using experimental data on the electron detection by satellites Elektro-L (positioned at a geostationary orbit) and Meteor-M no. 2 (positioned at a circular polar orbit at an altitude of about 800 km as the VERNOV satellite) will make it possible to study the spatial distribution pattern of energetic electrons in near-Earth space in more detail.

The academic Chibis-M microsatellite

This paper describes the scientific goals and design developments of the Chibis microsatellite platform and the Groza scientific equipment, which are aimed at studying new physical mechanisms of high-altitude electrical discharges in the atmosphere. A description of the Groza scientific equipment is presented, which is a united flying instrument that determines the basic requirements for the Chibis-M microsatellite. The problems of ground training of the space experiment, methods of launching the microsatellite in the ISS infrastructure into orbit, and command and telemetry control in flight, as well as the first scientific results, are presented.

Energetic Particles Impacting the Upper Atmosphere in Connection with Transient Luminous Event Phenomena: Russian Space Experiment Programs

In Russia several space missions are now planned to study transient luminous events in the atmosphere and high energy charged particles at satellite altitudes. The experimental goal is to investigate the origin of the high energy electrons and gamma‐ray quanta for specific transient luminous events (TLEs) and their role in the ionosphere‐magnetosphere system. Simultaneous measurements of electrons at the orbit of the satellite and TLE atmospheric radiation in many wavelength bands will be performed in two missions, Tatiana‐2 and RELEC. In the TUS mission UV transient event detection will be accompanied by measurements of the weak UV emission from the “seed” electrons of extensive air showers of extremely high primary energies.

The properties of gamma-radiation and high-energy neutron fluxes in "MIR" station orbit.

The study of radiation background components in the near-Earth space is very important for different branches of space research, in particular for space dosimetry and for the planning of gamma-astronomy experiments. Detailed information on the neutral components (gamma-quanta, neutrons) of background radiation was obtained during the Grif-1 experiment onboard Mir orbital station (OS). The measurements of fluxes of 0.05-50 MeV gamma-quanta and >30 MeV neutrons with a large area instrument (approximately 250 cm2 for gamma-quanta, approximately 30 cm2 for neutrons) as well as corresponding charged particle measurements (0.4-1.5 MeV electrons, 1-200 MeV protons) were made during this experiment. The background components induced by the stations own radiation as well as the albedo gamma-rays from the Earths atmosphere were revealed as the result of data analysis for about 600 h of observation. A mathematical model describing the latitude and energy dependences of atmospheric albedo gamma-rays as well as of those of gamma-quanta produced in the material of the station due to cosmic ray interactions was developed. An analytical approximation of the spectrum of induced gamma-rays from radioactive isotopes stored in the station and instruments materials is presented. The dynamics of gamma-quantum background fluxes during the geomagnetic disturbances of January 10-11, 1997 are discussed. An analytical representation of the latitude dependence of the integral flux of neutrons with >30 MeV is given.

Experiment with the SPR-N Instrument Onboard the CORONAS-F Satellite: Polarization, Temporal, and Spectral Characteristics of the Hard X-Ray of the Solar Flares

During the experiment with a polarimeter SPR-N onboard the CORONAS-F satellite, polarization of the X-ray of solar flares within the energy ranges of 20–40, 40–60, and 60–100 keV was measured according to Thomson scattering of X-ray photons in Beryllium plates with the following registration of the scattered photons by means of a system of six scintillation detectors based on Cs I(Na). As a result of observations for the period from August 2001 till December 2005, hard X-ray radiation was registered for 128 solar flares. During the event of 29 October 2003 degree of polarization of the radiation within the channels 40–60 and 60–100 keV exceeded 70 %, and within the channel 20–40 keV—50 %. Time profiles of the part of polarized radiation, orientation of the maximum polarization on the solar disc were obtained. The upper limit of the polarized radiation part for 25 events was estimated at the level of 8–40 %. For all registered flares time profiles (with resolution of up to 4 s) were registered, hard X-ray fluxes were determined, and spectrum factor was estimated. For the most powerful events which were observed during October–November 2003 and on January 20, 2005, the data on the dynamics of the characteristics of thermal and non-thermal components of X-radiation were obtained.

Space experiments aboard the Lomonosov MSU satellite

At present, the Institute of Nuclear Physics of Moscow State University, in cooperation with other organizations, is preparing space experiments onboard the Lomonosov satellite. The main goal of this mission is to study extreme astrophysical phenomena such as cosmic gamma-ray bursts and ultra-high-energy cosmic rays. These phenomena are associated with the processes occurring in the early universe in very distant astrophysical objects, therefore, they can provide information on the first stages of the evolution of the universe. This paper considers the main characteristics of the scientific equipment aboard the Lomonosov satellite.

Local structures of electrons with energies of hundreds of keV in the inner belt and the slot region observed from the Vernov satellite

The structure and dynamics of electron fluxes of subrelativistic energies in the range 235–300 keV at L < 4 during December 3–8, 2014, are analyzed according to the RELEC instrument onboard the Vernov satellite. Sharp changes in the parameters of the solar wind and the IMF were detected on December 6, but they did not lead to a magnetic storm. However, after the event of December 6, subrelativistic electron fluxes in the inner belt and the slot region were enhanced and structured. The dynamics of electron fluxes in the local transient bursts at L ~ 1.5–1.7 is considered in detail. It is shown that these bursts are associated with the development of the cyclotron instability in the tops of magnetic flux tubes near the inner belt maximum. The electron anisotropic index is estimated in these bursts. It is shown that in the beginning these bursts are anisotropic and that they become isotropic as the decay proceeds. The most likely chain of physical mechanisms that could lead to variations in electron fluxes of the inner belt described in this paper is presented. For the first time, the topological effects in stationary distributions of the electrons of the inner belt observed at low altitudes in the South Atlantic Anomaly region are explained.