Robotic optical telescopes global network MASTER II. Equipment, structure, algorithms

Presented paper describes the basic principles and features of the implementation of a robotic network of optical telescopes MASTER, designed to study the prompt (simultaneous with gamma radiation) optical emission of gamma-ray bursts and to perform the sky survey to detect unknown objects and transient phenomena. With joint efforts of Sternberg astronomical institute, High altitude astronomical station of the Pulkovo observatory, Ural state university, Irkutsk state university, Blagoveshchensk pedagogical university, the robotic telescopes MASTER?II near Kislovodsk, Yekaterinburg, Irkutsk and Blagoveshchensk were installed and tested. The network spread over the longitudes is greater than 6?h. A further expansion of the network is considered.     

RESULTS OF COMBINED ANALYSIS OF GROUND AND REMOTE SENSING INFORMATION IN THE STUDY OF MAJOR EARTHQUAKE CENTERS

Soil salinity is one of the most important problems affecting Egyptian soils. It is caused by: (1) a rising water table, or (2) the misuse of the irrigation water. Two Landsat images acquired in 1987 and 1999 were used to detect and monitor soil salinity over the Siwa Oasis, Western Desert, Egypt. DN values of these images were converted to percent reflectance. Inspection of Landsat images revealed that saline soils had an overall higher spectral reflectance in all spectral bands except the two MIR bands. The reflectance curves of saline soils show a strong relationship between the existence of salts in the soil and the difference between bands 4 and 5. A salinity index (SI) was calculated for both images. The majority of pixels in the 1987 image have salinity index values ranging between 0 and 0.2, whereas the values in the 1999 image histogram ranged between 0 and 0.4. These values indicate that soil salinity has increased twofold during the 12 years spanning the imagery. These values show a strong correlation with vegetation index images, in which the 1999 vegetation index image reveals the appearance of surface water lakes formed due to a rising water table. This study presents a model for the identification of soil salinity using remote sensing measurements in conjunction with piezometer readings taken during the time of image acquisition.     

The probabilistic approach to estimating the origination of certain types of extreme solar events

The probability of origination of superpower flares (super-flares) on the Sun, the power of which is higher than that of the observed flares, is discussed. The probabilistic approach, which makes it possible to find the analytical expression for the distribution of the observed values of any solar activity parameter and to extrapolate the obtained function to the range of values that were not observed previously, is proposed. The estimated probabilities of implementation of the Wolf number (400) and the flare proton fluxes in the Earth’s orbit (from 60000 to 160000 s⁻¹ cm⁻²) are presented as an example. It has been obtained that these events occur ones per 10 000 and 100 years, respectively.     

A Comprehensive Study of the Perseid Stream Bolide Using the Data of the SkyLine Baseline Video Monitoring System

Astronomy Reports - We carried out a detailed study of a bright meteor detected over the Khamar-Daban mountain range on August 12, 2020 at 14:37:35 UT by two automatic video monitoring stations...     

X-Ray Flares and Activity Complexes on the Sun in Solar Cycle 24

The statistical relationship between activity complex (ACs) on the Sun and solar flares with GOES X-ray classes higher than M1.0 (744 events) is analyzed for the 24th solar-activity cycle (before January 2019). All groups of sunspots are divided into three classes, corresponding to those in cores and branches of ACs and those outside of ACs. It is shown that 78% of the flares considered occur predominantly in groups of sunspots in AC cores and branches. The specific number of flares in AC cores exceeds the corresponding number in AC branches and outside of ACs by a factor of 2.5. 87% of LDE flares of the indicated classes, 82% of all strong proton flares generating fluxes of energetic protons at the Earth’s orbit, and 74% of all gamma-ray flares in Cycle 24 were associated with ACs.     

CHANGES IN SUNSPOT AND FLOCCULAR SOURCES OF RADIO EMISSION PRECEDING AN IMPORTANCE 2N FLARE ON 23 AUGUST 1988

Based on observations from the Siberian solar radio telescope, and invoking data from other observatories, we investigate preflare changes in the sunspot and floccular sources of radio emission and the development of an importance 2N flare in the chromosphere and corona in the active region on August 23, 1988.It has been ascertained that preflare changes became observable six hours prior to the flare onset and manifested themselves in intense flux fluctuations above the sunspot and in an enhancement of the source emission flux above the flocculus.It is shown that the flare onset is associated with a newly emerged magnetic flux in the form of a pore near the filament and with the appearance of radio sources above the filament. The flare was accompanied by type III radio bursts and a noise storm at meter wavelengths. Coronal mass ejection parameters are estimated from type III burst observations.     

The MASTER-II network of robotic optical telescopes. First results

The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered.     

Causes of the divergence of magnetic tube photospheric bases in AR 10930

It is traditionally considered that the bases of emerging magnetic tubes, which are observed as magnetic elements (tube ??sections??) moving away from one another at the photospheric level, diverge completely because tubes are loop-shaped below the photosphere. It is assumed that there may be more causes. The possible Ampere force contribution to the divergence of the photospheric bases of a coronal magnetic rope (the magnetic tube system) with a current has been considered based on the evolution of photospheric magnetic fields in active region 10930 during December 8?C13, 2006. It has been concluded that the contributions of the emergence and horizontal motion caused by the Ampere force to the divergence of magnetic tube photospheric bases with a current can be comparable in magnitude.     

Longitudinal factor in the spatial distribution of energetic solar flares

Discrete location of large flares near zero Carrington longitude results in artificial breaks within physically related flare clusters. This effect is eliminated by using the data presentation algorithm, which results in the conclusion that drifting zones of intensified sunspot formation (concentrated cores of activity complexes) and energetic flare generation exist in either hemisphere. The indicated L zone is hypothetically related to a non-asymmetric relic solar magnetic field or to the regions where large-scale convective cells, extending to the convective zone bottom, originate.     

Decay of activity complexes and the formation of coronal holes

Analysis of long-term measurements of solar magnetic fields and the flux of UV radiation from the Sun indicates a cause-effect relationship between activity complexs, their residual magnetic fields, and coronal holes. A comparison of the background magnetic fields of the Sun and the evolution of former activity complexes reveals unipolar magnetic regions that form after the decay of these complexes. The latitude and time evolution of unipolar magnetic regions in solar cycles 21–24 is studied. A North-South asymmetry in solar activity is manifest in the distribution of unipolar regions migrating toward higher latitudes. It is shown that, when residual magnetic fields of the opposite polarity reach the polar regions, this leads to a sign change of the polar magnetic field and a decrease in the area of polar coronal holes, or even their complete disappearance. These interactions can explain the triple sign change of the polar magnetic field of the Sun in cycle 21 and the short-term polarity reversals observed in 2010 and 2011.