Early Optical Observations of Gamma-Ray Bursts Compared with Their Gamma- and X-Ray Characteristics Using a MASTER Global Network of Robotic Telescopes from Lomonosov Moscow State University

We present the results of early observations for 130 error-boxes of gamma-ray bursts performed with the Mobile Astronomical System of TElescope-Robots (MASTER) global network of robotic telescopes from Moscow State University in fully automatic mode (2011–2017). Among them, GRB 130907A, GRB 120811C, GRB 110801A, GRB 120404A, GRB 140129B, GRB140311B, and GRB 160227A are considered in details. Among these 130 gamma-ray bursts, in the first 60 s after the trigger with the Swift, Fermi, INTEGRAL, MAXI, Lomonosov, and Konus-Wind orbital observatories, the MASTER was pointed on 51 gamma-ray bursts, being the leader in terms of the first pointing. Full observation automation and MASTER own real-time image processing software allowed us to obtain unique data on early optical emission that accompanied 44 gamma-ray bursts (GRB 110801A, GRB120106A, GRB 120404A, GRB 120811C, GRB 120907A, GRB 121011A, GRB 130122A, GRB 130907A, GRB 131030A, GRB 131125A, GRB 140103A, GRB 140108A, GRB 140129B, GRB 140206A, GRB 140304A, GRB 140311B, GRB 140512A, GRB 140629A, GRB 140801A, GRB140907A, GRB 140930B, GRB141028A, GRB 141225A, GRB 150210A, GRB 150211A, GRB 150301B, GRB 150323C, GRB 150404A/Fermi trigger 449861706, GRB 150403A, GRB 150413A, GRB 150518A, GRB 150627A, GRB 151021A, GRB 151215A, GRB 160104A, GRB 160117B, GRB 160131A, GRB 160227A, GRB 160425A, GRB 160611A, GRB 160625B, GRB 160804A, GRB 160910A, GRB 161017A, GRB 161117A, GRB 161119A). We obtain light curves for 13 gamma-ray bursts among the above listed ones and compare the data in the optical (MASTER), X-ray (Swift-XRT), and hard X-ray (Swift-BAT) ranges.     

Orbital Evolution of the Sun–Jupiter–Saturn–Uranus–Neptune Four-Planet System on Long-Time Scales

The four-planet problem is solved by constructing an averaged semi-analytical theory of secondorder motion by planetary masses. A discussion is given of the results obtained by numerical integration of the averaged equations of motion for the Sun–Jupiter–Saturn–Uranus–Neptune system over a time interval of 10 Gyr. The integration is based on high-order Runge–Kutta and Everhart methods. The motion of the planets is almost periodic in nature. The eccentricities and inclinations of the planetary orbits remain small. Short-period perturbations remain small over the entire interval of integration. Conclusions are drawn about the resonant properties of the motion. Estimates are given for the accuracy of the numerical integration.     

Revisiting the Determination of a Preliminary Orbit for a Celestial Body

Solar System Research - This paper revisits the classical problem of determining a preliminary orbit of a celestial body from angular observations. It is proposed to solve this problem using a...     

Sodar Sounding of the Atmospheric Boundary Layer: Review of Studies at the Obukhov Institute of Atmospheric Physics,Russian Academy of Sciences

Acoustic sounders (sodars) are the simplest and economically most effective devices for the ground-based remote sensing of the lower troposphere. Using sodars, a vast amount of knowledge about the structure and dynamics of the atmospheric boundary layer (ABL) has been obtained. The principal physics of sodar sounding was given by A.M. Obukhov in two short theoretical articles published in the Reports of the USSR Academy of Sciences in 1941: “On the Scattering of Sound in a Turbulent Flow” and “On the Distribution of Energy in the Spectrum of a Turbulent Flow.” In the late 1950s, Obukhov initiated the development of theoretical and experimental studies of sound scattering by turbulence, as well as a practical sodar sounding of the ABL at the Institute of Atmospheric Physics (IAPh). The present work is a short review of sodar applications in studies of the ABL based on results obtained at IAPh in the 1980s–2000s. The results of recent studies of low-level jets and Kelvin–Helmholtz billows in the stable stratified ABL are described in more detail.     

Generation of Intermediate Drift Bursts by Magnetohydrodynamic Waves in the Solar Corona

The plasma mechanism of radio emission generation in an inhomogeneous medium is investigated. In the model under study, the electron beam with loss-cone distribution generates upper-hybrid waves that, in turn, are transformed into radio emission. It is shown that the influence of the plasma density inhomogeneity limits the plasma waves’ intensity considerably due to variation in their wave vector. The results are used to interpret the intermediate drift (IMD) bursts. A model is proposed in which these bursts are reflections of propagating small-scale (with amplitudes of about 1% and sizes of hundreds of kilometers) magnetohydrodynamic (MHD) disturbances of magnetic tubes. It is shown that this model allows us to explain the spectral parameters of the bursts in question. At present, the lack of precise and independent data about the magnetic field does not allow us to decide definitively between the existing models (whistler or MHD waves) of the IMD bursts; nevertheless, if the proposed model is correct, it can be used to determine the characteristics of the coronal MHD waves.     

Formation of Thermocline in the Equatorial Zone of the Oceans

We study the formation of the vertical distribution of temperature in the upper layer of the oceans (0– 300m) at low latitudes (10°N-10°S) by using the nonlinear dependence of the vertical heat flow on the vertical temperature gradient with regard for the influence of the bulk absorption of solar radiation and heat sink on the temperature of water. The thermocline is formed under the condition that the modulus of temperature gradient attains values for which their subsequent increase leads either to insignificant variations of the heat flow or even to its decrease. We consider the possibility of solution of inverse problems for the evaluation of the heat-exchange coefficient and the parameter of the heat sink. For the Equatorial Atlantic considered as an example, we compare the theoretical results with the data of instrumental measurements.__________Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 10–16, November–December, 2004.     

Polar cap magnetic activity as a signature of substorm development

On the basis of the 5.46 min IMF data and the 3-min data on magnetic field at polar cap station Alert, various characteristics of the interplanetary magnetic field and polar cap magnetic activity are examined for the purpose of separating the substorm precursors. It is shown that the most suitable characteristics toward this aim are the following: 1.σ(B_Z)-index, defined as the 15-min sum of values of the southward (B_ZS) components of the IMF with an account of the negative gradient of the IMF vertical (B_Z) component; and 2.PC(B_Z)-index, defined as the 15-min sum of values of the polar cap magnetic disturbances, concerned with southward component B_ZS, with an account of variability of these disturbances. Every intense peak in the substorm activity is preceded by a corresponding increase in σ(B_Z) and PC(B_Z) indices. Thus, the conclusion is made that moderate and large substorms have a growth phase and as a result such substorms may be forecasted using the above indices.     

‘DEOS_CHAMP-01C_70’: a model of the Earth’s gravity field computed from accelerations of the CHAMP satellite

Performance of a recently proposed technique for gravity field modeling has been assessed with data from the CHAMP satellite. The modeling technique is a variant of the acceleration approach. It makes use of the satellite accelerations that are derived from the kinematic orbit with the 3-point numerical differentiation scheme. A 322-day data set with 30-s sampling has been used. Based on this, a new gravity field model – DEOS_CHAMP-01C_70 - is derived. The model is complete up to degree and order 70. The geoid height difference between the DEOS_CHAMP-01C_70 and EIGEN-GRACE01S models is 14 cm. This is less than for two other recently published models EIGEN-CHAMP03Sp and ITG-CHAMP01E. Furthermore, we analyze the sensitivity of the model to some empirically determined parameters (regularization parameter and the parameter that controls the frequency-dependent data weighting). We also show that inaccuracies related to non-gravitational accelerations, which are measured by the on-board accelerometer, have a minor influence on the computed gravity field model.     

Studying the solar corona above active regions from microwave observations during solar flares recorded by CORONAS-F satellite

In 2001–2003, 45 flares of hard X ray (HXR) and gamma ray radiation, identified with a particular active region (AR) that produced each event, were recorded during the experiments onboard the Russian Solar Observatory CORONAS-F using the SONG (solar neutrons and gamma ray quanta) instrument. The solar corona structure and dynamics above these ARs is studied on the basis of the microwave observations with two Russian radio telescopes RATAN-600 and Siberian Solar Radio Telescope (SSRT). The results are illustrated using the active region NOAA 9601 and flare of September 5, 2001 (～ 1430 UT) as an example. The flare is interesting because the energy of its gamma radiation exceeded 1 MeV, while its power was only M6.0 in soft X rays. Such a combination of the event characteristics is not too frequent, which indicates that the spectrum of the studied event was rather hard. The type of the source of microwave radiation above NOAA 9601 has been determined. Some properties of this-type sources of a diagnostic value for detecting ARs capable of producing HXR and gamma radiation are indicated.