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The possibilities of organizing an observation service for solar activity in order to provide space weather forecasting are considered. The most promising at this stage is the creation of a ground-based observation network. Such a network should include solar magnetographs that provide observation of large-scale magnetic fields of the Sun, and patrol optical telescopes designed to detect coronal mass ejections and solar flares. The data of magnetographic observations provide an assessment of recurrent solar winds. Patrol telescopes operating in continuous mode allow detecting the moments of eruption and determining the parameters of coronal mass ejections at the initial stage of acceleration. The network service can be supplemented with other types of observations in the radio and optical bands. The paper considers the composition of observational tools, as well as methods and models for forecasting., Comment: 26 pages, in Russian language, 14 figures, 1 table

On modern satellite observations of the Sun in the continuum with high spatial resolution, as well as on high-quality ground observations, a large number of small dark areas can be observed. These regions have no penumbra, have a contrast of up to 20% and are similar to solar pores. The characteristic area of such structures is $0.3\div5\ \mu$hm or $0.5\div5$ Mm. The number of such points in one image can be several hundred. The nature of such formations remains unclear. We have performed the selection of dark regions with a contrast of at least 3% of the level of the quiet Sun on the SDO/HMI observational data in the continuum for 2010-2020. We have studied the properties of "dark points, including the change with the cycle of activity, area distribution and contrast. We also compared such structures with the intensity of the magnetic field. We found that the number of dark dots with an area of less than 5 mhm, in which the magnetic field is not significant and is less than |B|<30 G, is from 60 to 80% of the total number of structures of this size. This means that these objects are not associated with magnetic activity. The existence of such structures can significantly affect the calculations of the sunspot index, since they can be mistaken as pores., Comment: 13 pages, 10 figures

We derive the plage area evolution over the last 12 solar cycles employing data from all Ca II K archives available publicly in digital form known to us, including several as yet unexplored Ca II K archives. We analyse more than 290,000 full-disc Ca II K observations from 43 datasets spanning the period 1892-2019. All images were consistently processed with an automatic procedure that performs the photometric calibration (if needed) and the limb-darkening compensation. The processing also accounts for artefacts plaguing many of the images, including some very specific artefacts such as bright arcs found in Kyoto and Yerkes data. We have produced a plage area time-series from each analysed dataset. We found that the differences between the plage areas derived from individual archives are mainly due to the differences in the central wavelength and the bandpass used to acquire the data at the various sites. We have empirically cross-calibrated and combined the results obtained from each dataset to produce a composite series of plage areas. "Backbone" series are used to bridge all the series together. We have also shown that the selection of the backbone series has little effect on the final plage area composite. We have quantified the uncertainty of determining the plage areas with our processing due to shifts in the central wavelength and found it to be less than 0.01 in fraction of the solar disc for the average conditions found on historical data. We also found the variable seeing conditions during the observations to slightly increase the plage areas during activity maxima. We provide the so far most complete time series of plage areas based on corrected and calibrated historical and modern Ca II K images. Consistent plage areas are now available on 88% of all days from 1892 onwards and on 98% from 1907 onwards., Comment: 23 pages, 19 figures, accepted for publication in A&A

Context. Systematic observations of magnetic field strength and polarity in sunspots began at Mount Wilson Observatory (MWO), USA in early 1917. Except for a few brief interruptions, this historical dataset continues till present. Aims. The sunspot field strength and polarity observations are critical in our project of reconstructing the solar magnetic field over the last hundred years. Here we provide a detailed description of the newly digitized dataset of drawings of sunspot magnetic field observations. Methods. The digitization of MWO drawings is based on a software package develope d by us. It includes a semi-automatic selection of solar limbs and other features of the drawing, and a manual entry of the time of observations, the measured field strength and other notes hand-written on each drawing. The data are preserved in a MySQL database. Results. We provide a brief history of the project and describe the results from digitizing this historical dataset. We also provide a summary of the final dataset, and describe its known limitations. Finally, we compare the sunspot magnetic field measurements with other instruments, and demonstrate that, if needed, the dataset could be continued using modern observations such as, for example, Vector Stokes Magnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) platform., Comment: 14 pages, 12 figures, 4 tables, Astronomy and Astrophysics, accepted

We analyzed a small flux rope eruption converted into a helical blowout jet in a fan-spine configuration using multi-wavelength observations taken by SDO, which occurred near the limb on 2016 January 9. In our study, first, we estimated the fan-spine magnetic configuration with the potential field calculation and found a sinistral small filament inside it. The filament along with the flux rope erupted upward and interacted with the surrounding fan- spine magnetic configuration, where the flux rope breaks in the middle section. We observed compact brightening, flare ribbons and post-flare loops underneath the erupting filament. The northern section of the flux rope reconnected with the surrounding positive polarity, while the southern section straightened. Next, we observed the untwisting motion of the southern leg, which was transformed into a rotating helical blowout jet. The sign of the helicity of the mini-filament matches the one of the rotating jet. This is consistent with the jet models presented by Adams et al. (2014) and Sterling et al. (2015). We focused on the fine thread structure of the rotating jet and traced three blobs with the speed of 60-120 km/s, while the radial speed of the jet is approx 400 km/s. The untwisting motion of the jet accelerated plasma upward along the collimated outer spine field lines, and it finally evolved into a narrow coronal mass ejection at the height of approx 9 Rsun . On the basis of the detailed analysis, we discussed clear evidence of the scenario of the breaking of the flux rope and the formation of the helical blowout jet in the fan-spine magnetic configuration., Comment: 18 pages, 12 figures, Accepted for publication in MNRAS Jouranl

This paper continues the cycle of authors' works on the detection of precursors of large flares (M5 and higher classes) in active regions (ARs) of the Sun by their microwave radiation and magnetographic characteristics. Generalization of the detected precursors of strong flares can be used to develop methods for their prediction. This paper presents an analysis of the development of NOAA AR 12242, in which an X1.8 flare occurred on December 20, 2014. The analysis is based on regular multiazimuth and multiwavelength observations with the RATAN-600 radio telescope in the range 1.65-10 cm with intensity and circular polarization analysis and data from the Solar Dynamics Observatory (SDO). It was found that a new component appeared in the AR microwave radiation two days before the X-flare. It became dominant in the AR the day before the flare and significantly decreased after the flare. The use of multiazimuth observations from RATAN-600 and observations at 1.76 cm from the Nobeyama Radioheliograph made it possible to identify the radio source that appeared before the X-flare with the site of the closest convergence of opposite polarity fields near the neutral line in the AR. It was established that the X-flare occurred 20 h after the total gradient of the magnetic field of the entire region calculated from SDO/HMI data reached its maximum value. Analysis of the evolution of the microwave source that appeared before the X-flare in AR 12242 and comparison of its parameters with the parameters of other components of the AR microwave radiation showed that the new source can be classified as neutral line associated source (NLS), which were repeatedly detected by the RATAN-600 and other radio telescopes 1-3 days before the large flares., Comment: 6 figures. The final publication is available at https://link.springer.com/journal/11478

On February 17 2016, the IceCube real-time neutrino search identified, for the first time, three muon neutrino candidates arriving within 100 s of one another, consistent with coming from the same point in the sky. Such a triplet is expected once every 13.7 years as a random coincidence of background events. However, considering the lifetime of the follow-up program the probability of detecting at least one triplet from atmospheric background is 32%. Follow-up observatories were notified in order to search for an electromagnetic counterpart. Observations were obtained by Swift's X-ray telescope, by ASAS-SN, LCO and MASTER at optical wavelengths, and by VERITAS in the very-high-energy gamma-ray regime. Moreover, the Swift BAT serendipitously observed the location 100 s after the first neutrino was detected, and data from the Fermi LAT and HAWC observatory were analyzed. We present details of the neutrino triplet and the follow-up observations. No likely electromagnetic counterpart was detected, and we discuss the implications of these constraints on candidate neutrino sources such as gamma-ray bursts, core-collapse supernovae and active galactic nucleus flares. This study illustrates the potential of and challenges for future follow-up campaigns., Comment: 23 pages, 13 figures, accepted by A&A on July 30 2017

Modern research in solar physics in Russia is a multifaceted endeavor, which includes multi-wavelength observations from the ground- and space-based instruments, extensive theoretical and numerical modeling studies, new instrument development, and cross-disciplinary and international research. The research is conducted at the research organizations under the auspices of the Russian Academy of Sciences and to a lesser extent, by the research groups at Universities. Here, we review the history of solar physics research in Russia, and provide an update on recent developments., Comment: 15 pages, 8 figures, accepted for publication, Asian Journal of Physics

The spatial and temporal distributions of solar filaments were analyzed using data from the Meudon Observatory for the period 1919-2003 and the Kislovodsk Mountain Astronomical Station for the period 1979-2014. We scanned $H_\alpha$ solar synoptic charts on which the filaments were isolated and digitized. The data on each filament comprise its location, length, area, and other geometrical characteristics. The temporal distributions of the number and total length of the filaments have been obtained. We also found latitudinal migration of filament locations with the solar cycle, and analyzed the longitudinal distribution and asymmetry of filaments in the northern and southern hemispheres, and other properties of their distribution. The tilt angles of filaments with respect the solar equator ($\tau$) were analyzed. On average, the eastern tips of filaments are closer to the poles than the western ones ($\tau \sim 10^\circ$). On the other hand, the filaments in the polar regions ($\theta>50^\circ$, where $\theta$ is the latitude) usually have negative tilts ($\tau <0^\circ$). The tilt angles vary with the phases of the 11 year sunspot cycle and are at their highest values in the epoch of the activity maximum. In the century-long modulation of the solar activity (Gleissberg cycle), the mean tilt angles of filaments in the mid-latitude zone ($\theta \sim \pm 40^\circ$) were maximum in the middle of the 20th century in solar sunspot cycles 18-19. We hereby propose using the statistical properties of solar filaments as an additional coherent measure of manifestation of the solar cycle which covers all latitudes and for which almost a century long systematically calibrated data series is available., Comment: 10 pages, 13 figures

We report early optical linear polarization observations of two gamma-ray bursts made with the MASTER robotic telescope network. We found the minimum polar- ization for GRB150301B to be 8% at the beginning of the initial stage, whereas we detected no polarization for GRB150413A either at the rising branch or after the burst reached the power-law afterglow stage. This is the earliest measurement of the polarization (in cosmological rest frame) of gamma-ray bursts. The primary intent of the paper is to discover optical emission and publish extremely rare (unique) high- quality light curves of the prompt optical emission of gamma-ray bursts during the non-monotonic stage of their evolution. We report that our team has discovered the optical counterpart of one of the bursts, GRB150413A., Comment: accepted, MNRAS, 2015

We report the early discovery of the optical afterglow of gamma-ray burst (GRB) 140801A in the 137 deg$^2$ 3-$\sigma$ error-box of the Fermi Gamma-ray Burst Monitor (GBM). MASTER is the only observatory that automatically react to all Fermi alerts. GRB 140801A is one of the few GRBs whose optical counterpart was discovered solely from its GBM localization. The optical afterglow of GRB 140801A was found by MASTER Global Robotic Net 53 sec after receiving the alert, making it the fastest optical detection of a GRB from a GBM error-box. Spectroscopy obtained with the 10.4-m Gran Telescopio Canarias and the 6-m BTA of SAO RAS reveals a redshift of $z=1.32$. We performed optical and near-infrared photometry of GRB 140801A using different telescopes with apertures ranging from 0.4-m to 10.4-m. GRB 140801A is a typical burst in many ways. The rest-frame bolometric isotropic energy release and peak energy of the burst is $E_\mathrm{iso} = 5.54_{-0.24}^{+0.26} \times 10^{52}$ erg and $E_\mathrm{p, rest}\simeq280$ keV, respectively, which is consistent with the Amati relation. The absence of a jet break in the optical light curve provides a lower limit on the half-opening angle of the jet $\theta=6.1$ deg. The observed $E_\mathrm{peak}$ is consistent with the limit derived from the Ghirlanda relation. The joint Fermi GBM and Konus-Wind analysis shows that GRB 140801A could belong to the class of intermediate duration. The rapid detection of the optical counterpart of GRB 140801A is especially important regarding the upcoming experiments with large coordinate error-box areas., Comment: in press MNRAS, 2015

In this work we introduce a new way of binning sunspot group data with the purpose of better understanding the impact of the solar cycle on sunspot properties and how this defined the characteristics of the extended minimum of cycle 23. Our approach assumes that the statistical properties of sunspots are completely determined by the strength of the underlying large-scale field and have no additional time dependencies. We use the amplitude of the cycle at any given moment (something we refer to as activity level) as a proxy for the strength of this deep-seated magnetic field. We find that the sunspot size distribution is composed of two populations: one population of groups and active regions and a second population of pores and ephemeral regions. When fits are performed at periods of different activity level, only the statistical properties of the former population, the active regions, is found to vary. Finally, we study the relative contribution of each component (small-scale versus large-scale) to solar magnetism. We find that when hemispheres are treated separately, almost every one of the past 12 solar minima reaches a point where the main contribution to magnetism comes from the small-scale component. However, due to asymmetries in cycle phase, this state is very rarely reached by both hemispheres at the same time. From this we infer that even though each hemisphere did reach the magnetic baseline, from a heliospheric point of view the minimum of cycle 23 was not as deep as it could have been.

In this work we take advantage of eleven different sunspot group, sunspot, and active region databases to characterize the area and flux distributions of photospheric magnetic structures. We find that, when taken separately, different databases are better fitted by different distributions (as has been reported previously in the literature). However, we find that all our databases can be reconciled by the simple application of a proportionality constant, and that, in reality, different databases are sampling different parts of a composite distribution. This composite distribution is made up by linear combination of Weibull and log-normal distributions -- where a pure Weibull (log-normal) characterizes the distribution of structures with fluxes below (above) $10^{21}$Mx ($10^{22}$Mx). We propose that this is evidence of two separate mechanisms giving rise to visible structures on the photosphere: one directly connected to the global component of the dynamo (and the generation of bipolar active regions), and the other with the small-scale component of the dynamo (and the fragmentation of magnetic structures due to their interaction with turbulent convection). Additionally, we demonstrate that the Weibull distribution shows the expected linear behavior of a power-law distribution (when extended into smaller fluxes), making our results compatible with the results of Parnell et al. (2009).

We present results of optical polarization observations performed with the MASTER robotic net for three types of objects: gamma-ray bursts, supernovae, and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A, polarization observations were obtained during very early stages of optical emission. For GRB100906A it was the first prompt optical polarization observation in the world. Photometry in polarizers is presented for Type Ia Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the linear polarization of SN 2012bh at the early stage of the envelope expansion was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3, QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer the degree of the linear polarization and polarization angle. The blazars OC 457 and 3C 454.3 were observed during their periods of activity. The results show that MASTER is able to measure substantially polarized light; at the same time it is not suitable for determining weak polarization (less than 5%) of dim objects (fainter than 16$^m$). Polarimetric observations of the optical emission from gamma-ray bursts and supernovae are necessary to investigate the nature of these transient objects., Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been corrected

This paper considers a possibility of magnetic-field generation by local turbulent flows at the bottom of convective zone. The cycle of magnetic-field generation in this model can be represented in the form of sequency of processes. There are vortexes with azimuth axis, similar with Taylor vortex, close to the bottom of convection zone. This leads to the generation of twisted flux tubes because of screw dynamo. The growth of magnetic field causes emersion of U- loops. During the process of emersion and extraction azimuthal field of flux tubes converts to axial field, and reaches the surface as bipolar of sunspots with U-shaped configuration. Due to differential rotation residual bipolar fields stretch out to the surface toroidal field and are shifted to the bottom of the convective zone by means of meridional flow at high latitudes. The direction of the toroidal field within the generation zone reverses its sign, and the cycle is repeated., Comment: 6 pages, 3 figures

Relative variations in the number of sunspots and sunspot groups in activity cycles have been analyzed based on data from the Kislovodsk Mountain Astronomical Station and international indices. The following regularities have been established: (1) The relative fraction of small sunspots decreases linearly and that of large sunspots increase with increasing activity cycle amplitude. (2) The variation in the average number of sunspots in one group has a trend, and this number decreased from 12 in cycle 19 to 7.5 in cycle 24. (3) The ratio of the sunspot index (Ri) to the sunspot group number index (Ggr) varies with a period of about 100 years. (4) An analysis of the sunspot group number index (Ggr) from 1610 indicates that the Gnevyshev-Ohl rule reverses at the minimums of secular activity cycles. (5) The ratio of the total sunspot area to the umbra area shows a long-term variation with a period about eight cycles and minimum in cycles 16-17. (6) It has been indicated that the magnetic field intensity and sunspot area in the current cycle are related to the amplitude of the next activity cycle., Comment: 7 pages; 6 figures

We applied automatic identification of sunspot umbrae and penumbrae to daily observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to study their magnetic flux (B) and area (A). The results confirm a previously known logarithmic relationship between the area of sunspots and their maximum flux density. In addition, we find that the relation between average magnetic flux (Bavg) and sunspot area shows a bimodal distribution: for small sunspots and pores (A < 20 millionth of solar hemisphere, MSH), Bavg = 800 G (gauss), and for large sunspots (A > 100 MSH), Bavg is about 600 G. For intermediate sunspots, average flux density linearly decreases from about 800 G to 600 G. A similar bimodal distribution was found in several other integral parameters of sunspots. We show that this bimodality can be related to different stages of sunspot penumbra formation and can be explained by the difference in average inclination of magnetic fields at the periphery of small and large sunspots., Comment: 13 pages, 5 figures, accepted for publication in Solar Physics

Erroneous submission in violation of copyright, removed by arXiv admin., Comment: Erroneous submission in violation of copyright

This paper considers the changes of average number of sunspots groups per day, aggregated by activity cycles Gn within the period since 1610 till present time. The relation of parameter Gn of the preceding and the following activity cycles has a long-term variation with the period of about 20 activity cycles. There is a positive correlation between the parameter Gn in the current cycle and analogous parameter in the following cycle Gn+1. For cycles N 10-21 for a pair of even and odd cycles the relation of parameter Gn corresponds to Gnevyshev-Ohl rule Godd/Geven>1. But in previous epochs the odd cycles could be less than the preceding even cycles, and it only proves the reversal of Gnevyshev-Ohl rule., Comment: 11 pages, 1 table, 4 figures

Measurements from the Mount Wilson Observatory (MWO) are used to study the long-term variations of sunspot field strengths from 1920 to 1958. Following a modified approach similar to that in Pevtsov et al. (2011), for each observing week we select a single sunspot with the strongest field strength measured that week and then compute monthly averages of these weekly maximum field strengths. The data show the solar cycle variation of the peak field strengths with an amplitude of about 500-700 gauss (G), but no statistically significant long-term trends. Next, we use the sunspot observations from the Royal Greenwich Observatory (RGO) to establish a relationship between the sunspot areas and the sunspot field strengths for Cycles 15-19. This relationship is then used to create a proxy of peak magnetic field strength based on sunspot areas from the RGO and the USAF/NOAA network for the period from 1874 to early 2012. Over this interval, the magnetic field proxy shows a clear solar cycle variation with an amplitude of 500-700 G and a weaker long-term trend. From 1874 to around 1920, the mean value of magnetic field proxy increases by about 300-350 G, and, following a broad maximum in 1920-1960, it decreases by about 300 G. Using the proxy for the magnetic field strength as the reference, we scale the MWO field measurements to the measurements of the magnetic fields in Pevtsov et al. (2011) to construct a combined data set of maximum sunspot field strengths extending from 1920 to early 2012. This combined data set shows strong solar cycle variations and no significant long-term trend (linear fit to the data yields a slope of $-0.2\pm$0.8 G year$^{-1}$). On the other hand, the peak sunspot field strengths observed at the minimum of the solar cycle show a gradual decline over the last three minima (corresponding to cycles 21-23) with a mean downward trend of $\approx$ 15 G year$^{-1}$.