V. S. Makhmutov

Solar particle events observed on MIR station.

Radiation impact of the SPEs on board the MIR space station and in the interplanetary space is discussed in the report. The data of the on-board radiation dosimeter R-16 were used to measure the SPE absorbed doses. Some of SPEs (such as September-October 1989 series of very large SPEs) were measured in detail by Liulin active high sensitive dosimetric instrument installed on board MIR station. MIR station orbit measurements of the absorbed doses are compared with the interplanetary absorbed doses from SPEs estimated by the data obtained by the METEOR satellite spectrometer. The equivalent dose beyond the magnetosphere resulting from the September 29, 1989 solar flare in a spacecraft module with ordinary shielding thickness (approximately 10 g/cm2 of Al) is far higher than the maximum permissible dose of acute single exposure (50 cSv) and comparable with the maximum permissible dose of 2 year mission (118 cSv). Such large SPEs are a serious hazard in interplanetary missions and call forth of special administrative countermeasures.

Analysis of atmospheric pressure and temperature effects on cosmic ray measurements

[1]xa0In this paper, we analyze atmospheric pressure and temperature effects on the records of the cosmic ray detector CARPET. This detector has monitored secondary cosmic ray intensity since 2006 at Complejo Astronomico El Leoncito (San Juan, Argentina, 31°S, 69°W, 2550u2009m over sea level) where the geomagnetic rigidity cutoff, Rc, is ~9.8u2009GV. From the correlation between atmospheric pressure deviations and relative cosmic ray variations, we obtain a barometric coefficient of –0.44u2009±u20090.01 %/hPa. Once the data are corrected for atmospheric pressure, they are used to analyze temperature effects using four methods. Three methods are based on the surface temperature and the temperature at the altitude of maximum production of secondary cosmic rays. The fourth method, the integral method, takes into account the temperature height profile between 14 and 111u2009km above Complejo Astronomico El Leoncito. The results obtained from these four methods are compared on different time scales from seasonal time variations to scales related to the solar activity cycle. Our conclusion is that the integral method leads to better results to remove the temperature effect of the cosmic ray intensity observed at ground level.

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.

On the relationship between quasi-biennial variations of solar activity, the heliospheric magnetic field and cosmic rays

Quasi-biennial oscillations (QBO) of solar activity (T ≈ 1–4 years) are considered to be a variation of basic solar activity, associated with the solar dynamo process. They are transferred into interplanetary space by the open magnetic flux of the Sun, generating QBO in the intensity of cosmic rays (CR). This paper discusses the observational characteristics of QBO in CR and their relationship with QBO on the Sun and in the interplanetary medium. The delay time of QBO in CR relative to the solar and heliospheric magnetic field suggests that the formation of QBO in the open magnetic flux of the Sun occurs within 3–5 months. The paper considers the question of the prominent periodicity of CR (T = 1.6 years) that has prevailed in CR and in the heliospheric magnetic field for more than 10 years but was not stable over 60 years of observations. Distinctions in the characteristics of QBO and long-term variations of CR suggest features of the mechanism of their formation.

Features of cosmic ray variation at the phase of the minimum between the 23rd and 24th solar cycles

The minimum between the 23rd and 24th cycles of solar activity was unusually deep and extended. The modulation of cosmic rays was minimal for the more than 70-year-long period of direct measurements. The data from stratospheric measurements by the Lebedev Physical Institute suggest that the flux of cosmic rays with more than 100 MeV/nucleon of energy exceeded the highest ever observed level (May 1965) by almost 12%. However, the ground-based neutron monitors sensitive to relatively high energies indicated that the flux of cosmic rays increased by less than 3%. This work compares the variations in the cosmic rays over periods of five minima of solar activity (the 20th to the 24th cycle). It is shown that in late 2008, an extra flux of particles with energies less than several GeV/nucleon was detected in the Earth’s orbit. A similar (though far smaller in scale) phenomenon was also observed in 1987 at the same orientation of the Sun’s magnetic field A < 0, but was not observed in epochs where A > 0.

Observation of cosmic ray and electric field variations in the surface atmosphere

The results of cosmic ray observations by the CARPET instrument at CASLEO (El Leoncito, Argentina, Rc ≈ 11.8 GV) in 2006–2008 are reported. The main attention is paid to CR variations due to electric field variations in the surface atmosphere.

Experimental investigations of quasistable radiation belts formed after solar proton events in September–October 1989 and March 1991 based on measurements made by “Liulin” dosimeter-radiometer on board the “MIR” space station

Abstract Since 1988 high sensitivity dosimeter-radiometer “Liulin” has been installed on board the MIR space station. Device measured absorbed dose rate and flux of penetrating particles. Results of measurements showed that after powerful solar proton events (SPE) September–October, 1989 and March, 1991 additional quasistable radiation belts were formed in the near earth space within the interval L=1.8−3.0. These “new” belts were observed as an additional maximums in flux (and sometimes dose) channels when crossing the SAA region. “New” belts were quasi stable and existed at least several months, decaying slightly after SPE. Dose to flux ratio analysis showed that major components of these belts were energetic electrons and protons arising in connection with preceding SPEs.

Proposal for a new radiation dose control system for future manned space flights

Radiation risk on a future long-duration manned space mission appears to be one of the basic factors in planning and designing the mission. Since 1988 different active dosimetric investigations has been performed on board the MIR space station by the Bulgarian-Russian dosimeter-radiometer LIULIN and French tissue-equivalent proportional counters CIRCE and NAUSICAA. A joint French-Bulgarian-Russian dosimetry experiment and the dosimetry-radiometry system RADIUS-MD have been developed for the future MARS-96 mission. On the base of the results and experience of these investigations a conception for a new radiation dose control system for the future orbital stations, lunar bases and interplanetary space ships is proposed. The proposed system which consists of different instruments will allow personal radiation control for crew members, radiation monitoring inside and outside each habitat, analysis and forecasting of the situation and will suggest procedures to minimize the radiation risk.

Precipitation of energetic magnetospheric electrons and accompanying solar wind characteristics

From 1957 up to the present time, the Lebedev Physical Institute (LPI) has performed regular monitoring of ionizing radiation in the Earth’s atmosphere. There are cases when the X-ray radiation generated by energetic magnetospheric electrons penetrates the atmosphere and is observed at polar latitudes. The vast majority of these events occurs against the background of high-velocity solar wind streams, while magnetospheric perturbations related to interplanetary coronal mass ejections (ICMEs) are noneffective for precipitation. It is shown in the paper that ICMEs do not cause acceleration of a sufficient amount of electrons in the magnetosphere. Favorable conditions for acceleration and subsequent scattering of electrons into the loss cone are created by magnetic storms with an extended recovery phase and with sufficiently frequent periods of negative Bz component of the interplanetary magnetic field (IMF). Such geomagnetic perturbations are typical for storms associated with high-velocity solar wind streams.

Application of multithreading programming to physical experiment

The necessity of using multithreading programming elements in developing programs to control complex and high-speed physical devices is discussed. The results of applications of the software developed on these principles in ground-based experimental setups for detecting cosmic rays and charged particles from an accelerator are presented.