Search

Strict registration is critical for imaging polarimetry; a highly accurate registration approach to the coronal image and imaging polarimetry of the Fe 6374 Å red coronal line have been researched in this paper. In order to improve the registration accuracy, this paper proposes the idea of image enhancement based on blind deconvolution combined with noise-adaptive fuzzy equalization algorithms. After image enhancement, the cross-correlation registration algorithm achieves better results. To diagnose a low-temperature corona, the polarization brightness of the red coronal line data and the Mauna Loa Solar Observatory (MLSO)/KCor data are compared to study the structural features and polarization information of the inner corona. We found that the polarization brightness radiation of the red coronal line has overall features similar to that of the MLSO/KCor data, but it has more detailed features, such as the cavity, polar plume, and interplume characteristics. Active regions, polar plumes, and interplumes show similar performance in red coronal line intensity, polarization brightness, degree of linear polarization, K-corona, and electron density along with the radial height. An interesting finding is that the polarization brightness of the red coronal line changes drastically along with the radial height across the cavity above the solar west limb, while neither the K-corona nor the electron density changes obviously. This seems to be a piece of possible evidence indicating that the red coronal line is not unpolarized in the cavity region.

The study presents the results of the correlation analysis for the average seasonal values of intensity of solar UV radiation (297–330 nm), as well as for the energy of the lines of solar spectral irradiance with total solar irradiance and total magnetic field of the Sun for the period of 2008–2018 (the 24th cycle of solar activity). The analysis is carried out using the spectral observations of solar UV radiation at Novolazarevskaya station (Antarctica), the SORCE spacecraft and WSO (Wilcox Solar Observatory) data. The dependence of the UVB-UVA radiation of 280–315 nm (UV-B) and 315–400 nm (UV-A) on changes in the total magnetic field of the Sun is revealed.

Solar activity changes with about 11-year periodicity, two 11-year cycles form a complete 22-year magnetic cycle of the Sun. Solar cycle 25 has recently begun, and it is important to know in advance what and when it will be at its maximum. The paper predicts the maximal sunspot (Wolf) number in solar cycle 25 separately in the northern and southern hemispheres. The absolute value of the polar magnetic field near the cycle minimum was used as a precursor of the cycle maximum. The values of solar polar magnetic field measured at the Wilcox Solar Observatory of Stanford University since 1976 and sunspot numbers in the N- and S-hemispheres in 1975–2020 (in solar cycles 21–24) are analyzed. For the time interval 1992–2020, sunspot numbers in the N- and S-hemispheres were used according to SILSO ( http://sidc.oma.be/SISLO , Version 2.0), and for the time interval 1975–1992, sunspot numbers were taken from the paper (Temmer et al., 2006, Astron. Astrophys. 2006, 447, 735) and reduced to the modern SILSO scale. Sunspot numbers in minima and maxima as well as corresponding times in solar cycles 21–24 in the N- and S-hemispheres were found. The correlation coefficient at different time lags between the smoothed monthly sunspot number and the modulus of the Sun’s polar magnetic field in the northern and southern hemispheres has been calculated. It was found that maximal correlation coefficients between these parameters are 0.587 at a time lag of 4.76 years in the N-hemisphere and 0.680 at a time lag of 5.45 years in the S-hemisphere. A qualitative forecast of maximal sunspot numbers in solar cycle 25 in the N- and S-hemisphere was obtained when the graphs of the polar fields were shifted forward in time relative to the sunspot numbers graphs by 4.76 and 5.45 years, respectively. This indicates that solar cycle 25 will be slightly stronger than the previous cycle. Using the absolute values of the mean polar magnetic fields during the 2 years interval just before the cycle minimum in the N- and S-hemispheres as precursors we found that predicted maximal sunspot numbers in the N- and S-hemisphere are 66 ± 17 and 83 ± 21, respectively. This quantitatively confirms that solar cycle 25 will be slightly (4–10%) more active than the previous one.

The potential to diagnose the beginning of the solar cycle based on the detection of small-scale magnetic formations, the magnetic nodes of ephemeral active regions in the zone of mid-heliolatitudes from 40° to 60°, has been studied. Magnetic nodes were detected at the stage of their emergence by the multifractal segmentation method, which was previously used to fix new magnetic fluxes of active regions in the zone of low heliolatitudes. Statistical estimates of the number of magnetic nodes recorded by this method were performed based on magnetograph data from the Synoptic Optical Long-term Investigations of the Sun of the National Solar Observatory (SOLIS NSO) for the 24th solar activity cycle, as well as for the beginning of the 25th activity cycle. A precursor of solar cycle 24 has been found in the form of a burst in the number of magnetic nodes in 2007–2008 that significantly exceeds the background value characteristic of the period 2011–2015. Two years later, the first active regions began to appear at latitudes of 30° ± 10°. A similar sequence of phases in the beginning of the cycle was found for cycle 25. Unlike the situation with solar cycle 24, the mass appearance of high-latitude active regions of cycle 25 occurred about 2.5 years after the burst in the number of nodes of ephemeral active regions.

We report on the results of development, fabrication, and analysis of broadband Mo/Si multilayer mirrors for spectroheliographs at the KORTES solar observatory, which operate in the spectral bands of 17–21 and 28–33 nm. The advantages of the stack approach are demonstrated. The results of measurements of reflection characteristics of mirrors are considered.

Based on the previously proposed steady-state 3D model of a solar facular knot, we have developed its modified version in which the solitary nature of the facular object is reflected: its magnetic field is sharply bounded in the radial direction. The facula temperature profile calculated for the steady state of such a magnetic structure is compared with the high-resolution filtergram taken in the photospheric TiO 7057 A line at Big Bear Solar Observatory on June 19, 2017, at the New Solar Telescope (with a 1.6-m aperture). The image shows two closely spaced very dark micropores with a diameter $${\sim}300$$ km each. The micropores are surrounded by a fan of thin, light, radially elongated fibrils resembling a sunspot penumbra. The theoretically calculated $$T$$ profile of the facular knot completely reproduces these morphological features of the object being modeled.

Solar radiation data are not easily available in many places over the world. Measurements of solar radiation in Mansoura either on a horizontal or tilted surfaces are too sparse to meet demand for scientific research and applications in agriculture and engineering. Estimation of daily global solar radiation is essential in Delta zone, since it is one of the most crowded areas and most agriculture and industrial activities are concentrated at this area where no solar observatory exist. Therefore, in this work, the hourly average total solar radiation data on horizontal, tilted (30° facing south) and normal surfaces is measured and compared with that data computed the clear sky model and the data recorded from the National Aeronautics and Space Administration (NASA) website [1]. Based on the MATrix LABoratory (MATLAB), a computer program has been developed to solve the clear sky model governing equations. The obtained results revealed that, the predicted solar radiation on horizontal, tilted, and normal surfaces were validated well with that measured. Results which are given in graphical form show that the data obtained from the clear sky model and that obtained from NASA website can be used as a reasonable and quick method for estimating the solar radiation when actual measurements are not available, .

The detection of Coronal Mass Ejections (CMEs) is an important prerequisite for establishing a CME event database and realizing the prediction of CME interplanetary propagation. The Lyman-alpha Solar Telescope (LST) aboard the ASO-S (Advanced Space-based Solar Observatory) satellite will be equipped with a white-light coronagraph. The images with CME detected will be contributed to various space weather prediction centers in China for CME early warning. The Visual Geometry Group (VGG) 16 convolutional neural network method is applied by us to automatically and effectively classify coronagraph images. Firstly, based on the image of the white light coronagraph of Large Angle and Spectrometric Coronagraph Experiment (LASCO) C2, we labeled the images according to whether a CME is observed. Then, the data set was used for training the VGG model. We find that the accuracy of the model in the test set classification reaches 92.5%. Next, according to the obtained classification results and combined with the space-time continuity rules, we corrected the mislabeling of images, and derived our final CME image sequences. Compared with the manual CME catalog of Coordinated Data Analysis Workshops (CDAW), the classified CME image sequences can include CME data more completely, and have higher detection sensitivity for weak CME structures.

Current sheets (CSs) are the main region where magnetic reconnections can convert magnetic energy into plasma thermal and kinetic energies. We have studied a CS in the streamer occurred on 3 January 2003 by combining the White-Light (WL) images observed by the Large Angle and Spectrometric Coronagraph (LASCO) and the EUV spectra detected by the Ultraviolet Coronagraph Spectrometer (UVCS). LASCO C2 WL data show that the speed of a blob in the CS increased from 60 km · s − 1 to 340 km · s − 1 with an acceleration of 60 m · s − 2 in its Field-of-View (FOV). By assuming the Light-of-Sight (LOS) depth of 0.3 – 1.5 R ⊙ , the average electron number density of the CS is (1.52 – 7.60) × 10 7 cm − 3 at the height of the UVCS slit. We investigate intensity distributions of the [Fe xviii ] 974 A and Ly α lines along the UVCS slit. It is shown that the intensity of the [Fe xviii ] line at the CS is significantly higher than those of the surroundings, and the deduced electron temperature range of the CS is (2.94 – 4.04) × 10 6 K during the studied period. However, the intensity of the Ly α line at the CS does not change much when compared with those of the surroundings, and within the CS the intensity on both sides are slightly higher than that in the center. It is possible that the plasma move faster in the center resulting in stronger Doppler dimming effect. Using the observed intensity ratio of the Ly α and [Fe xviii ] lines provided by the UVCS and the calculated electron temperature as constraints, we find that the theoretically calculated emissivity ratio of the Ly α and [Fe xviii ] lines is close to their observed intensity ratio when the plasma speed range is 237 – 254 km · s − 1 at the position of the CS. The collisional component of the Ly α line is about 42 % − 57 % of the radiative component in the CS within the speed range above. The streamer CS we studied has a higher plasma temperature and a faster blob speed than typical values in normal situations. The possible reason is that these two CMEs at the southern side enhanced the magnetic reconnection process in the CS, and more magnetic energy is released to heat and accelerate plasma. Our results on the CS can be regarded as pre-studies of the data analyses for the future mission of the Advanced Space-based Solar Observatory (ASO-S).

The Advanced Space-based Solar Observatory (ASO-S) is the China's first comprehensive solar dedicated satellite, scheduled to be launched around 2022. The Lyman-alpha (Ly α ) Solar Telescope (LST) is one of the payloads of the ASO-S, consisting of three scientific instruments and two Guide Telescopes (GTs). The scientific instruments include a Solar Disk Imager (SDI), a White-light Solar Telescope (WST), and a Solar Corona Imager (SCI), which are aimed to observe the whole evolving process of two types of violent eruptions on the Sun, i.e., solar flares and coronal mass ejections, in multiwavelengths with high temporal and spatial resolutions. To achieve this goal, all LST instruments have included an observation mode (event mode) dedicated to event observations. In this mode, all instruments take images at a higher cadence (the SCI takes full-frame coronal images while SDI and WST take only partial frame images around the eruption region). The time and location information of the eruption events can be effectively obtained by monitoring the local brightness enhancement of the onboard images processed with median filtering and pixel rebinning. The obtained information will provide an important electronic input for the automatic switching between different observation modes of LST.

The characteristics of turbulence over mountainous terrain are investigated with an aim to predict propagation of short-wavelength electromagnetic waves (including optical waves). For this purpose, long-term observations of the day- and night-time stratification of atmospheric turbulence are continued at the Sayany solar observatory. A new mobile AMK-03-4 hard-and-software system is used, which is designed for measuring the characteristics of turbulent meteofields. New experimental data are obtained on the turbulent scales of velocity V* (friction velocity) and temperature T*, which are important characteristics in the Monin–Obukhov similarity theory. A comparison of the experimental results with the data obtained by the authors earlier in different periods of time and in different climatic and geographical regions is performed. An experimental validation of the similarity theory postulates in the atmospheric boundary layer is provided. It is shown that the traditional similarity theory can be extended to an arbitrary (e.g., mountainous) boundary layer. This offers a solution to the problem of predicting the characteristics of turbulence in an anisotropic layer, including that in the mountain regions.

The paper analyzes meteorological and optical characteristics of the atmosphere at the Sayan Solar Observatory (SSO) and the future 3 m Large Solar Telescope (LST-3). We examine spatial features of changes in astroclimatic characteristics for the Sayan Solar Observatory and Baikal Astrophysical Observatory (BAO). We have obtained a vertical profile of the structural characteristic of air refractive index fluctuations for a low intensity optical turbulence along the line of sight. This profile is an important result because it will allow us to adjust the adaptive optics system of LST-3 to the best astroclimatic conditions when the correction efficiency is maximal. In order to analyze vertical profiles of optical turbulence characteristics and to assess the contribution of individual atmospheric layers to the isoplanatic angle for a minimum level of total turbulence, we give recommendations for the design of multi-conjugated adaptive optics in general and for LST-3 in particular.

During a deep extragalactic Lockman Hole sky survey with an area of 18.5 sq. deg, which was conducted when the SRG observatory was flying to the Lagrange point L2, the eROSITA telescope detected $${\sim}7000$$ X-ray sources. These objects were then provisionally identified and classified using the publicly accessible data of optical and infrared sky surveys by the SRGz machine learning system developed for this purpose at the Space Research Institute of the Russian Academy of Sciences. As a result, a number of new candidates for distant quasars ( $$z\sim 4$$ ) have been selected. The spectroscopic observations of the first two candidates from this list carried out with the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory have confirmed that these objects are actually distant quasars at redshifts 3.878 and 4.116 and are characterized by a high X-ray luminosity $${\sim}10^{45}$$ erg s $${}^{-1}$$ (2–10 keV). The results obtained allow one to count on the detection of a large number of distant quasars during a four-year all-sky survey of the SRG observatory begun in December 2019.

Sun–Jupiter decade-scale magnetic entanglement emerges from Wilcox Solar Observatory 1975-2021 N–S ≲150 μT mean-field data, as a global response of solar magnetic fields to the magnetar-type evolution of Jupiter ~2001–onward global magnetoactivity discovered recently in the 1–6 month (385.8–64.3 nHz) band of Rieger resonance. At extreme ≲20% field variance, the sudden Jovian deviation is so high it forced solar magnetoactivity devolution into inverse-matching response, at effectively moderate ≲1.5% mean-field variance. Thus as Jupiter magnetoactivity evolved sinusoidally, the Sun began mirror-compensating ~2002 (the epoch of Abbe number drop), reducing its magnetoactivity in decreasingly sinusoidal fashion to solar cycle 24 extreme minimum. For check, 2004-2021 WIND mission data revealed 7–103–102). Magnetic tangling of stars and hot (2–107 times more energetic than the strongest solar flare. Accordingly, the Sun ante-impulse locking is a shock-absorbing mechanism — routine shutter-response to Jupiter recurrent phasing into the flare-brown-dwarf state — with which the Sun enters a grand minimum (sleep mode). As Jupiter intermittently becomes an indirect driver of Earth’s climate, the Sun prepares to discharge stored energy as a non-extinction ~1032-erg superflare (currently overdue). The mechanism, in which warm/cold Jupiters too trigger (mild) superflares, possibly defends stars against incoming Jupiters., {"references":["Adams, F.C. (2011) Magnetically controlled outflows from hot Jupiters. Astrophys. J. 730:27. https://doi.org/10.1088/0004-637X/730/1/27","Aulbach, S., Heaman, L.M., Stachel, T. (2018) The Diamondiferous Mantle Root Beneath the Central Slave Craton. Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits. ISBN 9781629496399. https://doi.org/10.5382/SP.20.15","Bai, T. (2003) Hot Spots for Solar Flares Persisting for Decades: Longitude Distributions of Flares of Cycles 19-23. Astrophys. J. 585:1114-1123. https://dx.doi.org/10.1086/346152","Bai T. and Cliver E. W. (1990) A 154 day periodicity in the occurrence rate of proton flares. Astrophys. J. 363:299-309. https://doi.org/10.1086/169342","Basu, S. (2013) The peculiar solar cycle 24 — where do we stand? J. Phys. 440:012001. https://doi.org/10.1088/1742-6596/440/1/012001","Bose, S., Nagaraju, K. (2018) On the variability of the Solar Mean Magnetic Field: contributions from various magnetic features on the surface of the Sun. Astrophys. J. 862:35. https://doi.org/10.3847/1538-4357/aaccf1","Cane, H.V., Richardson, I.G., von Rosenvinge, T.T. (1998) Interplanetary magnetic field periodicity of ∼153 days. Geophys. Res. Lett. 25(24):4437-4440. https://doi.org/10.1029/1998GL900208","Carbonell, M., Oliver, R., Ballester, J.L. (1992) Power spectra of gapped time series: a comparison of several methods. Astron. & Astrophys. 264:350-360. https://ui.adsabs.harvard.edu/#abs/1992A&A...264..350C","Chauvin, G., Lagrange, A.-M., Zuckerman, B., Dumas, C., Mouillet, D., Song, I., Beuzit, J.-L., Lowrance, P., Bessell, M.S. (2005) A companion to AB Pic at the planet/brown dwarf boundary. Astron. Astrophys. 438(3):L29-L32. https://doi.org/10.1051/0004-6361:200500111","Danilović, S., Vince, I., Vitas, N., Jovanović, P. (2005) Time series analysis of long term full disk observations of the Mn I 539.4 nm solar line. Serb. Astron. J. 170:79-88. https://doi.org/10.2298/SAJ0570079D","Dowden, R.L. (1968) A Jupiter Model of Pulsars. Publications of the Astronomical Society of Australia 1(4):159–159. https://doi.org/10.1017/s132335800001122x","Fukuhara, M. (2020) Possible nuclear fusion of deuteron in the cores of Earth, Jupiter, Saturn, and brown dwarfs. AIP Advances 10:035126. https://doi.org/10.1063/1.5108922","Gonzalez, M.E., Dib, R., Kaspi, V.M., Woods, P.M., Tam, C.R., Gavriil, F.P. (2010) Long-term X-ray changes in the emission from the anomalous X-ray pulsar 4U 0142+61. Astrophys. J. 716:1345–1355. https://dx.doi.org/10.1088/0004-637X/716/2/1345","Griesmeier, J.-M., Stadelmann, A., Penz, T., Lammer, H., Selsis, F., Ribas, I., Guinan, E.F., Motschmann, U., Biernat, H.K., Weiss, W.W. (2004) The effect of tidal locking on the magnetospheric and atmospheric evolution of \"Hot Jupiters\". Astron. Astrophys. 425(2):753-762. https://doi.org/10.1051/0004-6361:2003568","Gurgenashvili, E., Zaqarashvili, T.V., Kukhianidze, V., Oliver, R., Ballester, J.L., Ramishvili, G., Shergelashvili, B., Hanslmeier, A., Poedts, S. (2016) Rieger-type periodicity during solar cycles 14–24: estimation of dynamo magnetic field strength in the solar interior. Astrophys. J. 826(1):55. https://doi.org/10.3847/0004-637X/826/1/55","Gurgenashvili, E., Zaqarashvili, T.V., Kukhianidze, V., Oliver, R., Ballester, J.L., Dikpati, M., McIntosh, S.W. (2017) North–South Asymmetry in Rieger-type Periodicity during Solar Cycles 19–23. Astrophys. J. 845(2):137-148. https://dx.doi.org/10.3847/1538-4357/aa830a","Kuznetsova, Yu.G., Pavlenko, E.P., Sharipova, L.M., Shugarov, S.Yu. (1999) Observations of Typical, Rare and Unique Phenomena in Close Binaries with Extremal Mass Ratio. Odessa Astron. Pub. 12:197-200. https://ui.adsabs.harvard.edu/#abs/1999OAP....12..197K","Lalitha S., Schmitt, J.H., Dash S. (2018) Atmospheric mass-loss of extrasolar planets orbiting magnetically active host stars. Mon. Not. R. Astron. Soc. 477(1):808–815. https://doi.org/10.1093/mnras/sty732","Lepping, R.P., Acuna, M.H., Burlaga, L.F. et al. (1995) The WIND magnetic field investigation. Space Sci. Rev. 71:207–229. https://doi.org/10.1007/BF00751330","Lockwood, M., Stamper, R. Wild, M. (1999) A doubling of the Sun's coronal magnetic field during the past 100 years. Nature 399:437–439. https://doi.org/10.1038/20867","Luhman, K.L., Adame, L., D'Alessio, P., Calvet, N., Hartmann, L., Megeath, S.T., Fazio, G.G. (2005) Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk. Astrophys. J. 635(1):L93. https://doi.org/10.1086/498868","Maehara, H., Shibayama, T., Notsu, S. et al. (2012) Superflares on solar-type stars. Nature 485:478–481. https://doi.org/10.1038/nature11063","Maehara, H., Shibayama, T., Notsu, Y., Notsu, S., Honda, S., Nogami, D., Shibata, K. (2015) Statistical properties of superflares on solar-type stars based on 1-min cadence data. Earth Planet. Sp. 67:59. DOI: https://doi.org/10.1186/s40623-015-0217-z Von Neumann, J. (1941) Distribution of the Ratio of the Mean Square Successive Difference to the Variance. Ann. Math. Statist. 12(4):367-395. https://doi.org/10.1214/aoms/1177731677","Von Neumann, J. (1941) Distribution of the Ratio of the Mean Square Successive Difference to the Variance. Ann. Math. Statist. 12(4):367-395. https://doi.org/10.1214/aoms/1177731677","Von Neumann, J. (1942) A Further Remark Concerning the Distribution of the Ratio of the Mean Square Successive Difference to the Variance. Ann. Math. Statist. 13(1):86-88. https://doi.org/10.1214/aoms/1177731645","Niroma, T. (2009) Understanding Solar Behaviour and its Influence on Climate. In: Natural drivers of weather and climate, Special Issue of Energy & Environment 20(1/2):145-159. https://doi.org/10.1260%2F095830509787689114","Omerbashich, M. (2021d) Magnetar-type bursting evolution of Jupiter global magnetoactivity since 1996. In review. https://doi.org/10.5281/zenodo.5508274","Omerbashich, M. (2021c) External forcing of Moon and Earth seismicity at Rieger periods. In review. https://doi.org/10.5281/zenodo.5069075","Omerbashich, M. (2021b) Extramartian forcing of Mars seismicity at Rieger periods. In review. https://doi.org/10.5281/zenodo.4921735","Omerbashich, M. (2021a) Non-marine tetrapod extinctions solve extinction periodicity mystery. Hist. Biol. 34 (29 March). https://doi.org/10.1080/08912963.2021.1907367","Omerbashich, M. (2009) Method for Measuring Field Dynamics. US Patent #20090192741, US PTO. https://worldwide.espacenet.com/publicationDetails/biblio?CC=US&NR=2009192741A1","Omerbashich, M. (2007) Magnification of mantle resonance as a cause of tectonics. Geodinamica Acta 20:6:369-383. ttps://doi.org/10.3166/ga.20.369-383","Omerbashich, M. (2006) Gauss–Vaníček Spectral Analysis of the Sepkoski Compendium: No New Life Cycles. Comp. Sci. Eng. 8(4):26–30. https://doi.org/10.1109/MCSE.2006.68 (Erratum due to journal error. Comp. Sci. Eng. 9(4):5–6. https://doi.org/10.1109/MCSE.2007.79; full text: https://arxiv.org/abs/math-ph/0608014","Omerbashich, M. (2003) Earth-model Discrimination Method. Ph.D. Dissertation, pp.129. ProQuest, USA. https://doi.org/10.6084/m9.figshare.12847304","Pagiatakis, S. (1999) Stochastic significance of peaks in the least-squares spectrum. J. Geod. 73:67-78. https://doi.org/10.1007/s001900050220","Pettersen, B.R. (1989) A review of stellar flares and their characteristics. Sol. Phys. 121:299–312. https://doi.org/10.1007/BF00161702","Raymond, S.N., Morbidelli, M. (2022) Planet formation: key mechanisms and global models. arXiv https://arxiv.org/abs/2002.05756. In: Biazzo, K., Bozza, V., Mancini, L., Sozzetti, A. (Eds.) Demographics of Exoplanetary Systems. Lecture Notes of the 3rd Advanced School on Exoplanetary Science. https://www.springer.com/gp/book/9783030881238","Rieger, E., Share, G.H., Forrest, D.J., Kanbach, G., Reppin, C., Chupp, E.L. (1984) A 154-day periodicity in the occurrence of hard solar flares? Nature 312:623–625. https://doi.org/10.1038/312623a0","Rubenstein, E.P., Schaefer, B.E. (2000) Are Superflares on Solar Analogues Caused by Extrasolar Planets? Astrophys. J. 529(2):1031. https://doi.org/10.1086/308326","Schaefer, B.E., King, J.R., Deliyannis, C.P. (2000) Superflares on Ordinary Solar-Type Stars. Astrophys. J. 529(2):1026. https://doi.org/10.1086/308325","Scharf, C.A. (2010) Possible constraints on exoplanet magnetic field strengths from planet-star interaction. Astrophys. J. 722:1547–1555. http://dx.doi.org/10.1088/0004-637X/722/2/1547","Scherrer, P.H., Wilcox, J.M., Svalgaard, L., Duvall, Jr. T.L., Dittmer, P.H., Gustafson, E.K. (1977) The mean magnetic field of the Sun: Observations at Stanford. Sol. Phys. 54:353–361. https://doi.org/10.1007/BF00159925","Simpson, J.F. (1968) Solar activity as a triggering mechanism for earthquakes. Earth Planet. Sci. Lett. 3:417-425. https://doi.org/10.1016/0012-821X(67)90071-4","Taylor, J., Hamilton, S. (1972) Some tests of the Vaníček Method of spectral analysis. Astrophys. Space Sci. 17:357–367. https://doi.org/10.1007/BF00642907","Tsurutani, B.T., Gonzalez, W.D., Lakhina, G.S., Alex, S. (2003) The extreme magnetic storm of 1–2 September 1859. J. Geophys. Res. 108:1268. https://doi.org/10.1029/2002JA009504","Tu, Z.-L., Yang, M., Zhang, Z.J., Wang, F.Y. (2020) Superflares on Solar-type Stars from the First Year Observation of TESS. Astrophys. J. 890:46. https://doi.org/10.3847/1538-4357/ab6606","Usoskin, I.G., Gallet, Y., Lopes, F., Kovaltsov, G.A., Hulot, G. (2016) Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxima. Astron. Astrophys. 587:A150. http://dx.doi.org/10.1051/0004-6361/201527295","Usoskin, I.G., Solanki, S.K., Kovaltsov, G.A. (2007) Grand minima and maxima of solar activity: new observational constraints. Astronomy & Astrophysics 471(1):301-309. https://doi.org/10.1051/0004-6361:20077704","Vaníček, P. (1969) Approximate Spectral Analysis by Least-Squares Fit. Astrophys. Space Sci. 4(4):387–391. https://doi.org/10.1007/BF00651344","Vaníček, P. (1971) Further Development and Properties of the Spectral Analysis by Least-Squares Fit. Astrophys. Space Sci. 12(1):10–33. https://doi.org/10.1007/BF00656134","Wells, D.E., Vaníček, P., Pagiatakis, S. (1985) Least squares spectral analysis revisited. Department of Geodesy & Geomatics Engineering Technical Report 84, University of New Brunswick, Canada. http://www2.unb.ca/gge/Pubs/TR84.pdf","Zaqarashvili, T.V., Carbonell, M., Oliver, R., Ballester, J.L. (2010) Magnetic Rossby waves in the solar tachocline and Rieger-type periodicities. Astrophys. J. 709(2):749–758. https://doi.org/10.1088/0004-637X/709/2/749"]}

The radio astronomy group in the Indian Institute of Astrophysics (IIA) has been carrying out routine observations of radio emission from the solar corona at low frequencies (${\approx}$40-440MHz) at the Gauribidanur observatory, about 100km north of Bangalore. Since IIA has been performing regular observations of the solar photosphere and chromosphere using different optical telescopes in its Kodaikanal Solar Observatory (KSO) also, the possibilities of obtaining two-dimensional radio images of the solar chromosphere using low-cost instrumentation to supplement the optical observations are being explored. As a part of the exercise, recently the group had developed prototype instrumentation for interferometric observations of radio emission from the solar chromosphere at high frequencies (${\approx}$11.2GHz) using two commercial dish TV antennas. The hardware set-up and initial observations are presented., Published in Solar Physics, 11 pages, 6 figures

Dissertação de Mestrado em Arqueologia e Território apresentada à Faculdade de Letras This Master's thesis in Archeology and Territory at the University of Coimbra focused on the analysis of the prehistoric rock art of two important testimonials in the municipality of Góis, central region of Portugal, more specifically: at Pedra Riscada and Pedra Letreira.The testimonials had already been the subject of extensive archaeological surveys twice, by traditional processes, so it was intended to verify whether new techniques for recording engravings and a more transdisciplinary approach would allow new contributions to their interpretations. Photogrammetry, archaeoastronomy, Bayesian statistics and experimental archaeology were used to illustrate symbol details and to strengthen or reject interpretive hypotheses.Photogrammetry makes it possible, under certain lighting conditions of the rocks, to build models that highlight details of symbols that are difficult to record by tracing on transparent plastic or by eye drawing. Therefore, this technique can be helpful as a complementary tool in archaeological surveys. Archaeoastronomy also proves to be very useful in strengthening hypotheses of places where it is suspected that there were rituals around the apparent movements of the sun or purely and simply astronomical interests. Experimental archaeology essentially allows rejecting interpretive hypotheses about processes, not proving to be a robust tool in the proof of a theory. Bayesian statistics, when the data are numerous and robust, allows us to predict the probability of other places in a country or region having similar rupestrian manifestations.We started from the principle that questioning guides the investigation, but this depends as much on paradigms as on disciplinary protocols as on the technical resources available.The Pedra Riscada, has a specific orientation in the landscape and its symbols have human biometric dimensions. It was theorized about its functionality and it is proposed, based on the observations and records made, that this monument could be a solar observatory from the early Bronze Age, regardless of having or not associated rituals.The Pedra Letreira, contains a vast set of concrete and abstract symbols that fits into a typology that has an extensive European dispersion. Its meanings were theorized and it is admitted that it is a communication system, that is, a kind of proto-writing. A chronology between the end of the Bronze Age/Iron Age is also proposed for this monument. Esta dissertação centra-se na análise da arte rupestre pré-histórica de dois importantes monumentos do concelho de Góis, região centro de Portugal, nomeadamente: Pedra Riscada e Pedra Letreira.Os monumentos já tinham sido alvo de levantamentos arqueológicos extensos, por duas vezes, pelo que se pretendeu verificar se novas técnicas de registo das gravuras e uma abordagem mais transdisciplinar permitiria dar novos contributos às suas interpretações. Utilizou-se a fotogrametria, a arqueoastronomia, a estatística Bayesiana e a arqueologia experimental para ilustrar pormenores de símbolos e robustecer ou rejeitar hipóteses interpretativas.A fotogrametria permite construir modelos que destacam pormenores dos símbolos, difíceis de registar por decalque ou desenho à vista, por isso deve ser olhada como uma ferramenta útil e complementar nos levantamentos arqueológicos. A arqueoastronomia também se revela útil no fortalecimento de hipóteses de locais onde se suspeita ter havido rituais em torno do movimento aparente do sol. A arqueologia experimental permite essencialmente rejeitar hipóteses interpretativas acerca de processos, não se demonstrando ser uma ferramenta robusta na prova de uma teoria. A estatística Bayesiana, quando os dados são numerosos e robustos, permite-nos prever a probabilidade de outros locais de um país ou região terem manifestações rupestres semelhantes.Partiu-se do princípio de que é o questionamento que orienta a investigação, mas este depende tanto dos paradigmas como dos protocolos disciplinares como dos meios técnicos de que se dispõe.A Pedra Riscada tem uma orientação específica na paisagem e os seus símbolos possuem dimensões biométricas humanas. Teorizou-se sobre a sua funcionalidade e propõe-se, tendo por base as observações e registos efetuados, que tal monumento seja um observatório solar do início da Idade do Bronze, independentemente de ter ou não, rituais associados. A Pedra Letreira contém um conjunto vasto de símbolos concretos e abstratos que se enquadram numa tipologia que tem uma dispersão europeia extensa. Teorizou-se sobre os seus significados e admite-se que se trate de um sistema de comunicação, ou seja, de uma proto-escrita. Também se propõe para tal monumento uma cronologia situada entre finais da Idade do Bronze/Idade do Ferro.

The Indian Institute of Astrophysics (IIA) has commissioned a low frequency (

A comparative analysis of the drift velocity of high-latitude prominences to the poles in solar cycles 13–24 is carried out. Data on the positions of prominences on weather maps from Wolfer (1887–1899) and (1904–1915) are used for the analysis. The data from digitized photographic plates with solar prominences obtained in the CaIIK line of the Kodaikanal Solar Observatory (India) for 1907–1956 are also used. These data are supplemented with daily observations of the prominences at Kislovodsk Mountain Astronomical Station (1957–2018). The dependence of the drift velocity of polar-crown prominences on the solar cycle strength is different for the northern and southern hemispheres. The drift velocity tends to decrease with increasing solar activity. This may be due to the fact that a strong large-scale magnetic field is observed at high latitudes before strong solar cycles. Its displacement rate, which is traced by the drift of polar prominences, then slows with the development of a cycle with an increasing polar field.

The longitudinal asymmetry of the photospheric magnetic field distribution is studied based on data from the Kitt Peak National Solar Observatory (synoptic maps for 1976–2016). Vector summation is used to weaken the effect of a stochastic component uniformly distributed along the longitude and to emphasize the stable nonaxisymmetric field component. Distributions of magnetic fields with different strength are considered: strong (B > 50 G), weak (B B > 5 G). It is shown that the longitudinal asymmetry in all the groups of fields varies in phase with the 11-year solar cycle. The asymmetry of the strong and medium fields varies in phase with the magnetic fluxes of these fields, whereas that of weak fields is in antiphase with the flux of the weak fields. The longitudinal distributions of the strong and medium magnetic fields resemble each other in shape: the distribution maximum is located at a longitude of ~180° during the ascent–maximum period of the solar cycle and at a longitude of ~0°/360° during the decrease–minimum period. Weak fields show the opposite picture: their distribution maximum is always located at the longitude of the strong and medium field minimum.

We provide 20 direct spectra that capture the variation of the solar spectrum composition with intensity. We correlate the value of the air mass, aerosol optical depth at 500 nm, precipitable water, and ozone with the cumulative irradiance for direct sunlight with the use of National Solar Radiation Database (NSRDB). We use the values of these atmospheric parameters to generate spectra that represent their corresponding cumulative irradiance levels with the use of SMARTS multiple scattering and transmission model. By simulation of the performance of a solar cell design under these 20 spectra and combination of the intensity-specific performance with the relative frequency of each irradiance level at a particular location from the NSRDB, we can predict tandem cell energy production across the United States. Through comparison of the energy production of ideal tandem cells with two to ten subcells as predicted by our model to energy production integrated over one year's worth of simulated spectra at nine locations across the United States as well as measured spectral irradiance from NREL's solar observatory, we find the error in our energy production estimate to be under 5% for ten subcells and under 3% for up to five subcells. We demonstrate the utility of the approach with a selection of prospective and ideal multijunction bandgap combinations.

We present the results of the multi- wavelength study of the two-ribbon solar flare on July 19, 2000 in the active region NOAA 9087. The evo- lution and morphological properties of the flare pro- ductive active region have been analyzed. The active region was growing rapidly and showed a complex mul- tipolar magnetic field configuration. It was large, pro- ducing many events, including the flare under consid- eration. The 3N/M6.4 two-ribbon flare was a promi- nent, long duration event in the active region evolution. According to Solar Geophysical Data (SGD) the flare lasted 2.5 hours. The flare energy release took place in many sites of the active region. We used combination of data from space and ground based observatories for study. The hard X-ray (HXR) and soft X-ray (SXR) data were obtained at the Yohkoh Telescopes (HXT and SXT) and Geostationary Operational Environmental Satellite (GOES). The full- disk magnetograms and EUV-images were provided by the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) and Extreme ultra- violet Imaging Telescope (EIT). We used the H α filter- grams from the Meudon spectroheliograph and white light images of Big Bear Solar Observatory (BBSO). All the data show continuously evolving SXR, EUV and H α features during the flare. The HXR and the type III radio bursts were observed at the flare onset. The first H α flare kernels and the surge, connected with the filament eruption, were initiated near a large positive-polarity sunspot. The main bright kernels of the flare occurred at the centre of the active region near magnetic neutral line, after that the flare ribbons appeared along it. It was found that HXR coronal source was located along a magnetic polarity inversion line of the active region. EUV loop structures indicate the observational evidence of a magnetic reconnection during the main phase of the flare.

Results of studies of motions in a filament during its slow ascent and eruption based on spectral observations obtained at the Sayan Solar Observatory are presented. SDO/HMI data on the longitudinal magnetic field and SDO/AIA images in the EUV are also considered. Short-period (∼5 min) vertical oscillations of the filament as a whole were detected during its ascent. An acceleration of the rise of the filament was accompanied by the rupture of an orthogonal loop above the filament, which was observed in 193 A EUV images obtained with SDO/AIA over a long time preceding the event. Two hours before the partial eruption of the filament, SDO/HMI data indicate an increase in the magnetic flux by 2 × 1019 Mx at the footpoints of the loop. The emission from the loop rupture piont propagated toward the east and west along a neutral line, and brightenings were observed at the boundaries of the filament channel. Emission loops were visible in all SDO/AIA channels, testifying to strong heating of the filament plasma. During the rapid phase of the eruption, the filament moved with an acceleration ∼21 m/s2. Hα images show the filament splitting into fragments parallel to its axis during the eruption. The results of these studies of the eruption of the filament are in agreement with other results in the literature, and are supplemented by new observational facts. Vertical oscillations (∼5 min) of the filament as a whole are observed before the ascent phase. During the ascent phase, an interaction of the filament with a higher-lying coronal loop is observed.

We present the results of optical spectroscopy for 39 quasar candidates at photometric redshifts zphot ≳ 3 from the catalog by Khorunzhev et al. (2016) (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. We have performed spectroscopy for new candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory. Predominantly X-ray bright quasar candidates that could be used to construct the X-ray luminosity function at luminosities LX,2–10 > 1045 erg s−1 have been selected. The purity of the candidates from K16 with a high X-ray flux has turned out to be lower than the purity of the quasi-random sample investigated by us previously. We have estimated the observing efficiency of quasar candidates as a function of their photometric redshift.

We present the first images of a coordinated campaign to follow active region NOAA 12709 on 2018 May 13 as part of a joint effort between three observatories (China-Europe). The active region was close to disk center and enclosed a small pore, a tight polarity inversion line and a filament in the chromosphere. The active region was observed with the 1.5-meter GREGOR solar telescope on Tenerife (Spain) with spectropolarimetry using GRIS in the He I 10830 \r{A} spectral range and with HiFI using two broad-band filter channels. In addition, the Lomnicky Stit Observatory (LSO, Slovakia) recorded the same active region with the new Solar Chromospheric Detector (SCD) in spectroscopic mode at H$\alpha$ 6562 \r{A}. The third ground-based telescope was located at the Fuxian Solar Observatory (China), where the active region was observed with the 1-meter New Vacuum Solar Telescope (NVST), using the Multi-Channel High Resolution Imaging System at H$\alpha$ 6562 \r{A}. Overlapping images of the active region from all three telescopes will be shown as well as preliminary Doppler line-of-sight (LOS) velocities. The potential of such observations are discussed., Comment: 4 pages, 3 figures, to appear in the proceedings of IAUS 354

Solar physics focuses on the star that is not only closest but most important to us. The study of solar physics is one of the most active interdisciplinary frontiers of astronomy, planetary and space science, plasma physics, etc. The eventual solution of many fundamental scientific problems would greatly benefit from breakthroughs in solar physics, e.g., problems such as the origin of magnetic field in astronomical objects, the formation and evolutionary mechanisms of the stellar magnetic cycle, the impact of stellar magnetic activities on the habitability of planets and the origin of life, and the forecast of solar eruptions to guard against adverse space weather effects. In the last ten years, solar physics has stepped into an era of multi-messenger, full electromagnetic spectrum, full time-domain, high-resolution, multi-scale, multi-view and high-precision detection. A new era is looming on the horizon with two revolutionary missions, namely, Parker Solar Probe, which was launched in 2018 and will probe the solar corona from as close as 6 million kilometers to the Sun’s surface, and Solar Orbiter, which will be launched in 2020 to image the Sun’s polar regions for the first time. In China, the first space mission dedicated to the Sun, the Advanced Space Based Solar Observatory (ASO-S), will be launched in 2021, targeting the next solar cycle. In addition, the Advanced Ground Based Solar Observatory (ASO-G) has been incorporated within the framework of national planning; under construction are two important instruments for solar physics, MUSER (Mingantu Ultrawide Spectral Radioheliograph) and AIMS (Accurate Infrared Magnetic field measurements of the Sun). Embracing the upcoming advancement in observing the Sun, we review in this article the prominent progresses made by Chinese scholars in the last ten years, mainly in studying the solar magnetic field, fine structures and dynamics of the lower atmosphere, and solar eruptions. At the frontier of solar magnetism, we have made headway in predicting the solar cycle, understanding the magnetic topology and the evolution of magnetic helicity, and modeling the coronal magnetic field. At the frontier of fine structures and dynamics of the lower atmosphere, we have advanced the understanding of not only new phenomena, such as ultraviolet bursts, but also traditional subjects, such as sunspot light bridges, Ellerman bombs, as well as mass and energy transfer from the lower to higher atmosphere. At the frontier of solar eruptions, we have made progress in identifying the eruption progenitor, clarifying its formation, structure, and evolution toward eruption as well as the subsequent propagation and interaction in interplanetary space, and understanding various aspects and consequences of magnetic reconnection, a fundament plasma process in the universe. On the basis of the review, we look forward to the future development of solar physics in China and to the prospect of Chinese scholars making even more substantial contributions to the solar physics research.

In the present article, complex optical UV bandpass filters with tantalum pentoxide and zirconium dioxide as high refractive index materials, respectively, have been manufactured on the EOSS® sputtering system. Four different bandpass filters with central wavelengths between 316 nm and 399 nm and a blocking up to 1100 nm were realized. Transmittance of the filters was higher than 80% although the band pass was located close to the absorption edge of the high index material. For two of the filters, ZrO2 was used as the high index material. It is demonstrated that the ZrO2 containing filters have very good optical properties and ZrO2 is a good alternative to the use of the costly HfO2. The bandpass filters will be used as order-sorting filters for the grating spectrograph of the Sunrise UV Spectropolarimeter and Imager (SUSI) onboard the balloon-borne solar observatory Sunrise III. The filters are designed to filter out unwanted light that hits the detectors. The observatory will be launched in June 2022. Among other topics, the mission is dedicated to the investigation of magnetic fields and convective plasma flows in the lower solar atmosphere.

Daniel K. Inouye Solar Telescope (DKIST) is designed to deliver accurate spectropolarimetric solar data across a wide wavelength range, covering a large field of view simultaneously using multiple facility instruments for solar disk, limb, and coronal observations. We show successful design and implementation of National Solar Observatory Coude Laboratory Spectropolarimeter, a custom metrology tool for efficient continuous broadband polarization calibration of the telescope mirrors through a coude laboratory focus. We compare multiple fitting techniques for the 10 to >140 variable DKIST system polarization models. We compare results with the first DKIST solar calibration observations and find small thermally forced retardance changes of ±0.2 deg and ±0.5 deg for two separate SiO2 retarders. Modulation matrices derived are stable to