The east-Siberian complex of SibIZMIR Solar Observatories

The Sayan Solar Observatory, the Tunkinskaya Radiophysical Observatory, and the Baikal Astrophysical Observatory of SibIZMIR have been described. Some results of the investigations carried out over the past years have been expounded. Clarifying solar activity mechanisms and the nature of solar magnetic fields, active regions and flares as well as solar wind are their main problems. In the interest of these investigations the Institute has initiated and developed laboratory-scale simulation of plasma processes.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

The abundance of cadmium in the solar atmosphere

The solar spectrum at 3261 Å has been studied using the spectrograph at the Oslo Solar Observatory. From analysis of this wavelength region and recent results at 5085 Å, a solar cadmium abundance log N _Cd = 1.86 ± 0.15 is obtained.     

A Search for Periodicities in F10.7 Solar Radio Flux Data

The radio frequency emission at 10.7 cm (or 2800 MHz) wavelength (considered as solar flux density) out of different possible wavelengths is usually selected to identify periodicities because of its high correlation with solar extreme ultraviolet radiation as well as its complete and long observational record other than sunspot related indices. The solar radio flux at 10.7 cm wavelength plays a very valuable role for forecasting the space weather because it is originated from lower corona and chromospheres region of the Sun. Also, solar radio flux is a magnificent indicator of major solar activity. Here in the present work the solar radio flux data from 1965 to 2014 observed at the Domimion Radio Astrophysical Observatory in Penticton, British Columbiahas been processed using Date Compensated Discrete Fourier Transform (DCDFT) to identify predominant periods within the data along with their confidence levels. Also, the multi-taper method (MTM) for periodicity analysis is used to validate the observed periods. Present investigation exhibits multiperiodicity of the time series F10.7 solar radio flux data around 27, 57, 78, 127, 157, 4096 days etc. The observed periods are also compared with the periods of MgII Index data using same algorithm as MgII Index data has 99.9% correlation with F10.7 Solar Radio Flux data. It can be observed that the MgII index data exhibits similar periodicities with very high confidence levels.Present investigation also clearly indicates that the computed results are very much confining with the results obtained in different communication for the similar data of 10.7 cm Solar Radio Flux as well as for the other solar activities.

     

The results of coronal investigation at the September 22, 1968 solar eclipse

The 1968 Abastumani Astrophysical Observatory Solar Eclipse Expedition obtained photographic records of the polarization and intensity of the solar corona on September 22 from a site of the South Urals (Western Siberia). A photometric study of the corona was carried out. Polarization has been computed both in a total corona and in some of its streamers. The coronal intensity I _k and I _F components are separated. Electron concentrations and temperatures are computed.     

Helium 10830 Å measurements of the Sun

Measurements of the Sun in the near-infrared He i 10830 Å absorption line were performed using the echelle spectrograph with a dispersion of 6.71 mÅ per pixel at the Vacuum Tower Telescope (German Solar Telescopes, Teide Observatory, Izaña, Tenerife, Spain) on May 26, 1993. These measurements were compared with full-disc soft X-ray images of the Sun (Japanese solar satellite Yohkoh), full-disc solar images in H (Big Bear Solar Observatory), full-disc solar images in the He i 10830 Å line (National Solar Observatory, Kitt Peak) and with full-disc microwave solar maps at 37 GHz (Metsähovi Radio Research Station). In the He 10830 Å line the Sun displays a limb darkening similar to that in the visible part of the spectrum. Active regions and H filaments show a strong absorption in the He 10830 Å line, whereas the absorption is weak in coronal holes.     

中国出口双折射滤光器

中国科学院南京天文仪器研制中心在20世纪80年代研制35cm太阳磁场望远镜滤光器取得巨大的成功，其在双折射滤光器领域内的水平，已被国际太阳物理界公认。1989年以来，已向日本和韩国出口了11台复杂而昂贵的Lyot滤光器，并已在有关国立天文台和天文馆投入常规观测。最近，还为国外客户修复3台Lyot滤光器，它们都是德国和法国在30年前生产的。     

On the Measurements of Full-Disk Longitudinal Magnetograms at Huairou Solar Observing Station

Reliable information on the distribution of magnetic fields across the whole surface of the Sun is urgently needed to predict conditions in the solar corona, in the interplanetary medium, and in the near-Earth space (space weather). Several space- and ground-based solar instruments currently provide full-disk magnetograms. However, these measurements sometimes differ very significantly, which makes a cross-calibration of different datasets and searching for the reasons for such differences a very crucial task. Here, we analyze the Huairou Solar Observing Station (HSOS) Solar Magnetism and Activity Telescope (SMAT) full-disk line-of-sight magnetograms in comparison with magnetograms taken at the Solar Dynamic Observatory/Helioseismic and Magnetic Imager (SDO/HMI) and Solar Telescope for Operative Predictions (STOP) instruments. We show systematic differences between original SMAT magnetograms and those of other telescopes. The differences are caused by some SMAT instrumental problems, which we investigate. We suggest methods for compensating for these effects that have improved the quality of SMAT magnetograms. These methods will enable us to use SMAT measurements to solve many solar physics problems that are related to studying global solar magnetism and space weather.     

CMOS图像传感器在太阳磁场观测中的应用研究

磁场是太阳物理的第1观测量,当前太阳磁场观测研究正迈向大视场、高时空分辨率、高偏振测量精度以及空间观测的时代.中国首颗太阳观测卫星—先进天基太阳天文台(ASO-S)也配置了具有高时空分辨率、高磁场灵敏度的全日面矢量磁像仪(FMG)载荷,针对FMG载荷的需求,讨论了大面阵、高帧频互补金属氧化物半导体(Complementary Metal Oxide Semiconductor, CMOS)图像传感器应用于太阳磁场观测的可行性.首先,基于滤光器型太阳磁像仪观测的原理,比较分析了目前CMOS图像传感器(可用的或是可选的两种快门模式)的特点,指出全局快门类型更适合FMG;其次搭建了CMOS传感器实验室测试系统,测量了CMOS图像传感器的像素增益及其分布规律;最后在怀柔太阳观测基地的全日面太阳望远镜上开展了实测验证,获得预期成果.在这些研究基础上,形成了FMG载荷探测器选型方向.     

Editorial: solar radiophysics—recent results on observations and theories

Solar radiophysics is a rapidly developing branch of solar physics and plasma astrophysics. Solar radiophysics has the goal of analyzing observations of radio emissions from the Sun and understanding basic physical processes operating in quiet and active regions of the solar corona. In the near future, the commissioning of a new generation of solar radio observational facilities, which include the Chinese Spectral Radio Heliograph（CSRH） and the upgrade of the Siberian Solar Radio Telescope（SSRT）, and the beginning of solar observations with the Atacama Large Millimeter/submillimeter Array（ALMA）, is expected to bring us new breakthrough results of a transformative nature. The Marie-Curie International Research Staff Exchange（MC IRSES） “RadioSun” international network aims to create a solid foundation for the successful exploitation of upcoming solar radio observational facilities, as well as intensive use of the existing observational tools, advanced theoretical modeling of relevant physical processes and observables, and training a new generation of solar radio physicists. The RadioSun network links research teams from China,Czech Republic, Poland, Russia and the UK. This mini-volume presents research papers based on invited reviews and contributed talks at the 1st RadioSun workshop in China. These papers cover a broad range of research topics and include recent observational and theoretical advances in solar radiophysics, MHD seismology of the solar corona, physics of solar flares, generation of radio emission, numerical modeling of MHD and plasma physics processes, charged-particle acceleration and novel instrumentation.     

Discovery in 1960 of the Flare Nimbus Phenomenon and Changes with Time in Its Interpretation

During the International Geophysical Year (IGY, 1957/1958) Dunsink Observatory near Dublin in Ireland was a World Data Centre for Solar Activity. In this circumstance, Hα Lyot Heliograph records secured on a daily basis between 07:00 – 14:00 UT at the Cape of Good Hope (then an integral link in a network of similar instruments contributing during the IGY to global monitoring of solar chromospheric activity) were routinely sent to Dunsink for analysis and dissemination. The investigations carried out at Dunsink on these data resulted, inter alia, in the discovery of the Flare Nimbus phenomenon. The nimbus comprises a dark expanding halo seen in the plage regions around major flares at, or within a few minutes of, the time of flare maximum intensity in Hα light. It reaches its greatest extent about 30 minutes after flare maximum. Its maximum dimensions (estimated visually) lie in the range 2 – 4×10⁵ km and its duration ranges from ∼ 1 – 2 hours. Within the nimbus the striation pattern is either completely destroyed or loses its pre-flare configuration. An account of this phenomenon and its interpretation appeared primarily, although not exclusively, in the locally produced Dunsink Observatory Publications which are not now easily accessible to the world community of solar researchers. Also, at around the time when the nimbus was first identified and recorded in Lyot Heliograph data at several observatories, techniques in solar physics shifted towards high resolution narrow field observations. Under these conditions no further examples of the nimbus were recorded and the subject has remained dormant over several decades. The present paper again places the scientific results obtained with regard to the nimbus in the public domain, together with an account of the evolution within the scientific community of an explanation of this phenomenon. It is suggested here for the first time, in the light of present day data concerning coronal mass ejections (CMEs) and coronal dimming, that the nimbus provides a signature of CME-related reorganization of the magnetic field in the chromosphere (such that the transverse magnetic field component decreases and transforms into the line of sight component as the vector field stretches out). Coronal dimming provides a complementary signature of CME-related mass depletion in the corona.     

Visualization of three-dimensional datasets

The effective visualization of three-dimensional (3d) datasets, both observationally and computationally derived, is an increasing problem in solar physics. We present here plots of computational data derived from the 3d reconstruction of the magnetic field of a loop system, rendered as anaglyphs. By combining images of the same 3d object from two slightly different angles a realistic and useful 3d effect is obtained, aiding data visualization. The application of the same technique to real solar data (such as from the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO)) is discussed.     

Flow Sources and Formation Laws of Solar Wind Streams

The large-scale stream structure of the solar wind flow is studied in the main acceleration zone from 10 to 40 solar radii from the Sun. Three independent sets of experimental data were used: radio astronomical observations of radio wave scattering using the large radio telescopes of the Lebedev Physical Institute; dual-frequency Doppler solar wind speed measurements from the Ulysses Solar Corona Experiment during the spacecraft's two solar conjunctions in summer 1991 and winter 1995; solar magnetic field strength and configuration computed from Wilcox Solar Observatory data. Both the experimental data on the position of the transonic region of the solar wind flow and the solar wind speed estimates were used as parameters reflecting the intensity of the solar wind acceleration process. Correlation studies of these data with the magnetic field strength in the solar corona revealed several types of solar wind flow differing in their velocities and the location of their primary acceleration region.     

Taiwan Oscillation Network

The Taiwan Oscillation Network (TON) is a ground-based network to measure solar intensity oscillations to study the internal structure of the Sun. K-line full-disk images of 1000 pixels diameter are taken at a rate of one image per minute. Such data would provide information onp-modes withl as high as 1000. The TON will consist of six identical telescope systems at proper longitudes around the world. Three telescope systems have been installed at Teide Observatory (Tenerife), Huairou Solar Observing Station (near Beijing), and Big Bear Solar Observatory (California). The telescopes at these three sites have been taking data simultaneously since October of 1994. Anl – v diagram derived from 512 images is included to show the quality of the data.     

Transition region and coronal plasmas: instrumentation and spectral analysis

The plasma conditions in the solar atmosphere and, in particular, in coronal holes are summarized, before space-borne instrumentation for observing these regions in vacuum-ultraviolet light is briefly introduced with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) as example. Spectroscopic measurements of small plasma jets are then analyzed in detail. Magnetic reconnection is thought to be responsible for heating the corona of the Sun as well as accelerating the solar wind by converting magnetic energy into thermal and kinetic energies. The continuous outflow of the fast solar wind from coronal holes on ‘open’ field lines, which reach out into interplanetary space, then requires many reconnection events of very small scale sizes – most of them probably below the resolution capabilities of present-day instruments. Our observations of such an event have been obtained with the Solar and Heliospheric Observatory (SOHO) providing both high-resolution imaging and spectral information for structural and dynamical studies. We find whirling or rotating motions as well as jets with acceleration along their propagation paths in close spatial and temporal vicinity to the coronal jet. This revised version was published online in July 2006 with corrections to the Cover Date.     

Height stratification of solar magnetic fields in cycle 23

The radial component Br of magnetic field was calculated in the potential approximation and the synoptic maps of Br for several heights in the Solar atmosphere were constructed based on observations of the photospheric magnetic field made on the old magnetograph at the US Kitt Peak National Observatory and on the new SOLIS magnetograph at the US National Solar Observatory for cycle 23 (the years 1997–2009). Parameters of large-scale structures of magnetic field with positive and negative polarities were determined at seven heights in the Sun’s atmosphere—from the photosphere (H = Ro) to H = 2.5 Ro (Ro is the Solar radius). The processes of polar reversal for polar fields and changing of the sector structure of the field at middle latitudes were observed. Characteristic lifespans and rotations were ascertained. The general picture of variations of the large-scale solar magnetic field during cycle 23 was put forward. Two types of boundaries of large magnetic structures at various heights were identified.     

Study of Differences Between Sunspot and White Light Facular Area Data Determined from SDO/HMI and SOHO/MDI Observations

Sunspot and white light facular areas are important data for solar activity and are used, for example, in the study of the evolution of sunspots and their effect on solar irradiance. Solar Dynamic Observatory??s Helioseismic and Magnetic Imager (SDO/HMI) solar images have much higher resolution (??0.5????pixel^?1) than Solar and Heliospheric Observatory??s Michelson Doppler Imager (SOHO/MDI) solar images (??2????pixel^?1). This difference in image resolution has a significant impact on the sunspot and white light facular areas measured in the two datasets. We compare the area of sunspots and white light faculae derived from SDO/HMI and SOHO/MDI observations. This comparison helps the calibration of the SOHO sunspot and facular area to those in SDO observations. We also find a 0.22 degree difference between the North direction in SDO/HMI and SOHO/MDI images.     

The Teide Observatory

The Teide Observatory in the Canary Islands is, at present, a well-known nucleus for solar physics research. In this contribution, the facilities at the Observatory, which now houses one of the IRIS network instruments, are presented.     

New vacuum solar telescope and observations with high resolution

The New Vacuum Solar Telescope(NVST) is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including measurements of the solar magnetic field. NVST is the primary ground-based facility used by the Chinese solar research community in this solar cycle. It is located by Fuxian Lake in southwest China, where the seeing is good enough to perform high resolution observations. We first introduce the general conditions at the Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of the solar photosphere and chromosphere are also shown.     

Use of the FITS World Coordinate System by STEREO/SECCHI

The World Coordinate System (WCS) is a standard for embedding coordinate information in a Flexible Image Transport System (FITS) header. Its first extensive use within solar physics is by the Sun Earth Connections Coronal and Heliospheric Investigation (SECCHI) telescope suite onboard the Solar Terrestrial Relations Observatory (STEREO). The WCS formalism assists in SECCHI data analysis in several ways: First of all, the spherical effects associated with the extremely wide fields-of-view of the Heliospheric Imager (HI) telescopes can be handled in a completely unambiguous and standard fashion. Of particular importance is that WCS positional keywords allow spacecraft-ephemeris information to be embedded within the FITS header without depending on mission-specific keywords. Ephemeris data is critical to the three-dimensional analysis that the STEREO mission is designed for. We also show how the WCS software in SolarSoft\textsf{SolarSoft} can be used to relate STEREO data to other missions such as the Solar and Heliospheric Observatory (SOHO). The ability of WCS to support a parallel celestial right ascension (R.A.)/declination (Dec) coordinate system and the use of WCS for COR1 synoptic maps are also discussed. The advantages that STEREO derived from WCS can equally be applied to other solar missions, in particular Solar Orbiter, and should be adopted by all future missions.     

The Radiometric and Pointing Calibration of SECCHI COR1 on STEREO

COR1 is the innermost coronagraph of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite aboard the twin Solar Terrestrial Relations Observatory (STEREO) spacecraft. The paired COR1 telescopes observe the white-light K-corona from 1.4 to 4 solar radii in a waveband 22.5 nm wide centered on the Hα line at 656 nm. An internal polarizer allows the measurement of both total and polarized brightness. The co-alignment of the two COR1 telescopes is derived from the star λ Aquarii for the Ahead spacecraft, and from an occultation of the Sun by the Moon for Behind. Observations of the planet Jupiter are used to establish absolute photometric calibrations for each telescope. The intercalibration of the two COR1 telescopes are compared using coronal mass ejection observations made early in the mission, when the spacecraft were close together. Comparisons are also made with the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO) C2 and Mauna Loa Solar Observatory Mk4 coronagraphs.