bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Number of Isolating Integrals in Systems with Three Degrees of Freedom
Authors: Froeschle Claude 
Published: July 2016

AbstractDynamical systems with three degrees of freedom can be reduced to the study of a four-dimensional mapping. We consider here, as a model problem, the mapping given by the following equations:
We have found that as soon as b ≠ 0, i.e. even for a very weak coupling, a dynamical system with three degrees of freedom has in general either two or zero isolating integrals (besides the usual energy integral).
Small-Scale Structures in Active Regions
Authors: Keller Christoph U. 
Published: July 2016

AbstractWithin the last few years significant progress has been made in our understanding of the small-scale structures in active regions. Here I present some of the newest findings obtained by using speckle interferometric techniques. There exist continuum bright points with a contrast of about 30% that are cospatial with strong magnetic fields. The observations are consistent with the assumption that some facular and network bright points are the white-light signature of magnetic fluxtubes with a diameter of about 200 km. Magnetic elements larger than about 300 km are mainly darker than the average quiet sun. Their properties are similar to what has been called magnetic knots or invisible sunspots. In highly magnetic areas there is no clear relationship between continuum intensity and magnetogram signal at the smallest spatial scales. The magnetic field of pores extends beyond the dark umbra. There radially elongated structures may appear that are similar to penumbral filaments in sunspots.
The Sizes of Active Regions and Convective Triggering of the Buoyant Loop Instability
Authors: Petrovay K. , Szakály G. 
Published: July 2016

AbstractThe sizes of solar active regions were quantitatively studied using Debrecen Heliographic Results 1977 data. The size-total area dependence was also examined. The size of a region was defined as the distance between the area-weighted mean positions of p- and f-polarity subgroups at the time when the total (umbral + penumbral) area of the spot group is at its maximum. Excluding the groups for which this occurred on the invisible hemisphere and other dubious cases, 68 active regions were left in the present one-year sample. Despite the smallness of this sample, the average size of the regions was found to be 58 400 km with a relatively low error of 3000km (though the individual regions show a considerable scatter in size). It is proposed that the toroidal magnetic flux tubes lie in a sufficiently subadiabatic layer to be linearly stable and they are only destabilized by finite-amplitude convective disturbances that lift parts of them into the unstable layers. In such circumstances the typical size will be determined by the horizontal correlation length of the finite disturbances, thereby explaining the observed size.
Monochromatic Images of Sunspots in Linearly Polarized Radiation and Structure of their Magnetic Fields
Authors: Shi-Hui Ye , Jie-Hai Jin 
Published: July 2016

AbstractThe monochromatic images of unipolar sunspots in the Stokes parameters Q and U of magneto-sensitive lines display a complicated structure. This is caused by the magneto-optical effect and also connected with the 3-D structure of spot magnetic fields. In the process of numerical simulation it is possible to check the regularities of the change of the angle of inclination of magnetic lines of force with distance from spot center.
Ten Years of the Okayama Vector Magnetograph
Authors: Makita Mitsugu , Sakurai Takashi , Shibasaki Kiyoto , Koyano Hisashi 
Published: July 2016

The vector magnetograph of the Okayama Astrophysical Observatory (Makita et al. 1985a,c) is equipped on the 65cm solar coude telescope with the 10m Littrow spectrograph. Results of observations are vector magnetograms, velocitygrams, maps of the broadband polarizations, maps of the magnetic lines of force, and maps of the electric currents. Their examples are given in figure 1. The data books, which give the vector magnetograms, have been published every year since 1983.Calibrations of the polarization degree and the overall accuracy were discussed (Makita et al. 1982, 1987; Makita and Li 1992). The accuracy of the polarization measurement is 10−3for the line observation and 10−4 for the continuum observation. Conversion of the polarization degrees to the magnetic field vector has been tried by Sakurai (1987) with the use of the weak field theory and the observed magnetic field strength of sunspots. A simultaneous observation of the same active region was once made with the Sayan Observatory (Makita et al. 1985b). Distributions of the magnetic polarity were quite similar and azimuths of the magnetic field agreed very well.
Filter Magnetograph Measurements at Meudon Observatory
Authors: Dollfus Audouin , Moity Jacques 
Published: July 2016

SummaryWe report observational studies of solar active regions n°6150 and n°6850 during cycle 22. Observations were carried out with a tunable monochromatic birefringent filter coupled with a line-shifter and a Stokesmeter as well as with a spectro-magnetograph, both at Meudon Observatory. AR n°6150 is typical of emerging flux regions, while AR n° 6850, with a complex preceding δ-spot, exhibits characteristic configurations of the transverse magnetic field for flaring activity: shear along the neutral line, and curvature coupled with anomalous Evershed mass motions.
The Interaction of Weak and Strong Fields on the Sun
Authors: Zirin Harold 
Published: July 2016

AbstractThe problems associated with unresolved flux elements are discussed. It is pointed out that the hypothesis that these fields are strong does explain various problems of solar magnetic fields, but, as all invisible phenomena, is difficult to test. It is pointed out that Zeeman splitting measurements, which give the true field, have revealed field strengths down to the lower limit of conventional spectroscopy (about 400 gauss) for years. Not one spectrogram showing larger splitting in plages or network has been produced. The power-law distribution of weak-field strengths suggests a hierarchy of field strengths, and the simple arithmetic of weak-field elements and tiny pores is on the edge of ruling out strong fields, and further improvement in resolution should do so.Observations in the 12μ lines have shown plage fields of a few hundred gauss and broadening of the σ components due to field variation within the field of view. These data have been explained away on the basis of height variation in the field, but the requisite transverse field strength or center-limb behavior are not observed.
Analysis of EUV, Microwave, and Magnetic Field Observations of Solar Plage
Authors: Brosius J W , Davila J M , Jones H P , Thompson W T , Thomas R J , Holman G D , White S M , Gopalswamy N , Kundu M R 
Published: July 2016

AbstractWe obtained simultaneous images of solar plage on 7 May 1991 with Goddard Space Flight Center’s Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and the NASA/NSO spectromagnetograph at Kitt Peak. Using intensity ratios of Fe XVI to Fe XV emission lines, we find that the coronal plasma temperature is 2.5 ± 0.3 ×lO6 K throughout the region. The column emission measure ranges from 2.6 × 1027 to 1.3 × 1028 cm−5. The calculated structure and intensity of the 20 cm wavelength thermal bremsstrahlung emission from the hot plasma observed by SERTS is quite similar to the observed structure and intensity of the 20 cm microwave emission observed by the VLA. Using the revised coronal iron abundance of Meyer (1991, 1992), we find no evidence for either cool absorbing plasma or for contributions from thermal gyroemission. Combining the observed microwave polarization and the SERTS plasma parameters, we calculate a map of the coronal longitudinal magnetic field. The resulting values, ~ 30 – 60 Gauss, are comparable to extrapolated values of the potential field at heights of 5,000 and 10,000 km.
On the Formulae for Calculating the Magnetic Field in the Source of Solar Microwave Bursts
Authors: Zhao Ren-Yang 
Published: July 2016

AbstractBased on the theory of gyro-synchrotron radiation from both thermal and nonthermal electrons, and adopting the relation between the peak frequency and the corresponding rise time of microwave bursts, we have derived several analytical formulae for calculating the magnetic field in the source regions of solar microwave bursts.
Panoramic Analyzer of Radio Spectra — Instrument for Measurements of Coronal Magnetic Fields on the Sun
Authors: Bogod V. M. , Vatrushin S. M. , Abramov-Maximov V. E. , Tsvetkov S. V. , Dikij V. N. 
Published: July 2016

The study of solar radio emission in a wide (covering many octaves) wavelength range is of great importance for plasma diagnostics of all types of solar activity. Here we describe a new spectroanalyzer covering a wide range in frequency from 1 to 18 GHz, which is used at the RATAN-600 radio telescope beginning 1991 December 20. Coronal magnetic fields have been measured with the various radio astronomical methods presented in these proceedings by Gelfreikh et al. and Bogod et al.Of special value are collaborative spectral-polarization observations using the RATAN-600 and high-spatial resolution observations with the VLA and WSRT (Akhmedov et al. 1986; Bogod et al. 1992; Alissandrakis et al. 1992).
Diagnostics of the Velocity Field in the Lower Atmosphere of Solar Flares
Authors: Cheng Fang , Su-Ying Yin , Ming-De Ding , Hiei Eijiro 
Published: July 2016

AbstractBased on the analyses of Call K line profiles of 12 solar flares, the characteristics of the red asymmetry of Call K line are summarized. Non-LTE calculations indicated that a downward motion of plasma above the temperature minimum region (TMR) as well as a contracting motion of plasma toward TMR can well explain the red asymmetry observed at the Ki positions. The typical velocity is 10-30 km s−1. This result is consistent with the observations of metallic lines of solar flares.
Line-of-Sight and Proper Motions in the Flaring June 1991 ( NOAA 6659 ) Active Region
Authors: Bumba Václav , Klvaňa Miroslav , Kalman Bela , Györi Lajos 
Published: July 2016

AbstractWe present the results of comparison of photoelectrically and photographically made measurements of Doppler and proper motions with the distribution of the longitudinal magnetic field and spot topology in this large complex region.
A Sufficient Condition for Krall’s Criterion and its Modifications
Authors: Linxiang Wu 
Published: July 2016

AbstractIn order to determine the sense of the photospheric transverse magnetic field measured with a magnetograph, it is shown that: (1) If the magnetic lines of force through the photospheric plane are both divergent and convex upward, Krall’s criterionis true for the transverse field B⊥ much more strongly than for the longitudinal field Bz and the inequality in general becomes(2) If the magnetic lines of force are only divergent upward, we have instead the inequalityfor a force-free field.
Properties of Emerging Bipolar Active Regions
Authors: Harvey Karen L. 
Published: July 2016

AbstractCharacteristics and the emergence pattern of bipolar active regions are investigated using NSO/KP full disk magnetograms. Discussed in this paper are two samples of newly emerged bipolar regions: 9492 ephemeral regions and 978 active regions. Their distributions in size, latitude, and orientation are compared. It is concluded that ephemeral regions are the small scale end of a wide spectrum of active regions.
Observations of Waves and Oscillations in the Solar Magnetic Fine Structure
Authors: Fleck B. , Deubner F.-L. , Schmidt W. 
Published: July 2016

AbstractWe study the oscillatory behaviour of small-scale magnetic flux-tube concentrations and their immediate surroundings by analysing high spatial resolution time series of spectra of four Zeeman sensitive lines (Fe I 5247.1, Cr I 5247.6, Fe I 5250.2, Fe I 5250.7) taken simultaneously in left-hand and right-hand circularly polarized light with the Echelle spectrograph at the Vacuum Tower Telescope in Izaña, Tenerife. The velocity field inside the magnetic elements is dominated by the 5-min oscillations which also show up as periodic variations in the relative amplitude asymmetry of the Stokes V profiles. In other parameters as for instance the Stokes V peak separation we cannot detect an oscillatory component. Neither the magnetic line ratio nor the thermal line ratio is affected by the 5-min oscillations, although the latter reveals remarkable spatiotemporal variations.
Siphon Flow Across the Magnetic Neutral-Line of an Active Region
Authors: Solanki S.K. , Rüedi I. , Rabin D. 
Published: July 2016

AbstractWe present accurate measurements, based on the g = 3 line at 1.5648/µm, of the field strength and longitudinal velocity in the vicinity of the magnetic neutral-line of a solar active region. We find that very close to the neutral line the field strength and the flow velocity are correlated in the sense that the magnetic polarity with the larger field strength is associated with a downflow, while the polarity with the weaker field shows an upflow. This is exactly the signal predicted by theoretical models of siphon flows, and constitutes the first reliable detection of a siphon flow on the sun.
Low Density Drivers of Strong Interplanetary Shocks
Authors: Hewish A. 
Published: July 2016

AbstractThe theory that most, if not all, interplanetary shocks are caused by coronal mass ejections (CMEs) faces serious problems in accounting for the strongest shocks. The difficulties include (i) a remarkable absence of very strong shocks during solar maximum 1980 when CMEs were prolific, (ii) unrealistic initial speeds near the Sun for impulsive models, (iii) the absence of rarefaction zones behind the shocks and (iv) sustained high speed flows following shocks which are not easily explained as consequences of CME eruptions. Observations of the proton temperature near 1 AU indicate that strong shock drivers have properties similar to high speed streams emitted by coronal holes. Eruptions of fast solar wind from coronal holes influenced by solar activity can explain the occurrence of the strongest interplanetary shocks.
Shock Waves Propagation in the Turbulent Interplanetary Plasma
Authors: Chashei I.V. , Shishov V.I. 
Published: July 2016

AbstractEffect of turbulence on interplanetary shock waves propagation is considered. It is shown that background turbulence results in the additional shock wave deceleration which may be comparable with the deceleration due to plasma sweeping. The turbulent deceleration is connected with the energy losses due to the strong turbulence amplification behind the moving shock front.
Inferences of Plasma Parameters from Coronal Hole Observations
Authors: Habbal Shadia Rifai 
Published: July 2016

AbstractThe temperature in the acceleration region of the solar wind remains one of the most elusive parameters to measure. Knowledge of the temperature as well as its gradient in the inner corona is fundamental for placing constraints on physical mechanisms thought to be responsible for the coronal heating process, as well as for understanding the flow properties of the solar wind. Estimates of the helium abundance is essential for understanding the puzzling behavior of heavier ions in the solar wind. As an illustration of the difficulties and uncertainties involved in the inferences of plasma parameters in the solar wind acceleration region, the inference of electron temperature and helium abundance will be described. Prospects for future observations will be briefly discussed.
Anisotropic Angular Broadening in the Solar Wind
Authors: Anantharamaiah K.R. , Gothoskar Pradeep , Cornwell T.J. 
Published: July 2016

AbstractWe present Very Large Array observations at wavelengths of 2, 3.5, 6, and 20 cm, of angular broadening of radio sources due to the solar wind in the region 2-16 solar radii. Angular broadening is anisotropic with axial ratios in the range 2-16. Larger axial ratios are observed preferentially at smaller solar distances. Assuming that anisotropy is due to scattering blobs elongated along magnetic field lines, the distribution of position angles of the elliptically broadened images indicates that the field lines are non-radial even at the largest heliocentric distances observed here. At 5R⊙, the major axis scattering angle is ~ 0.7" at λ = 6 cm and it varies with heliocentric distance as R−1.6. The level of turbulence, characterized by the wave structure function at a scale of 10 km along the major axis, normalized to λ = 20 cm, has a value 20±7 at 5R⊙ and varies with heliocentric distance as R−3. Comprison with earlier results suggest that the level of turbulence is higher during solar maximum. Assuming a power-law spectrum of electron density fluctuations, the fitted spectral exponents have values in the range 2.8–3.4 for scales sizes between 2–35 km. The data suggests temporal fluctuations (of up to 10%) in the spectral exponent on a time scale of a few tens of minutes. The observed structure functions at different solar distances do not show any evidence for an inner scale; the upper limits are 1 km at 2R⊙ and 4 km at 13R⊙. These upper limits are in conflict with earlier determinations and may suggest a reduced inner scale during solar maximum.
North-South Asymmetry of the Polar Solar Wind and Some Characteristics of Solar Magnetic Field
Authors: Girish T.E. , Gopkumar G. 
Published: July 2016

AbstractWe have found correlated variations of the yearly averaged north-south asymmetry in the polar solar wind speed (Δsol) and the ratio of the zonal quadrupolar to the zonal dipolar contribution in the inferred coronal magnetic field during the declining phase of sunspot cycle 21. A physically meaningful association between Δsol and some polar solar magnetic field proxies is also observed during the low sunspot activity periods of the above cycle.
Solar Activity Dependence of Interplanetary Disturbances
Authors: Manoharan P.K. 
Published: July 2016

AbstractInterplanetary scintillation measurements obtained inside 200 R⊙ using the Ooty Radio Telescope during August 1986 - April 1991 have been analysed to study the interplanetary disturbances (or events) and their occurrence rates at various phases of the solar cycle. The disturbances are identified by the increase in the level of scintillation compared with the expected value. In total, 735 events have been identified. The results show a rate of 0.49 events per day near solar maximum and a low rate of 0.16 events per day during minimum of activity. The results are compared with coronal mass ejection (CME) rates and transients rates obtained from the Doppler scintillation measurements.
IPS Observations of Short-Time Scale Interplanetary Activity
Authors: Gothoskar Pradeep , Rao A. Pramesh 
Published: July 2016

AbstractWe have carried out a program of continuous Interplanetary Scintillation (IPS) monitoring of the interplanetary activity using Ooty Radio Telescope (ORT). From May 1990 to March 1991, during the 22nd solar maximum, a few radio sources were monitored to provide long stretches of IPS data with a high-time resolution of few minutes. These observations covered 0.3 to 0.8 AU region (12° to 70° elongations) around the sun at several heliographic latitudes. During the observation, we detected 33 short-time scale IPS events which had significant variation in the scintillation index and solar wind velocity. These were considered to be due to travelling interplanetary disturbances.A multi-component model of plasma density enhancement was developed to estimate the geometry and physical properties of these IPS events. Detailed analysis of 20 of these events suggests, 1. fast IPS events were interplanetary signatures of Coronal Mass Ejections (CMEs), 2. the average mass and energy of these events was ~ 1016 gm and 1033 erg respectively, 3. 80% of IPS events were associated with X-ray flares on the sun and 50% were associated with geomagnetic activity at earth. Detailed study of the multi-component model suggests IPS observations at smaller elongations (hence at higher radio frequencies) are more suited to detect fast-moving interplanetary disturbances such as produced by CMEs.
IPS Observations at STELAB for the Fruitful Coming Decade
Authors: Asai K. , Ishida Y. , Kojima M. , Maruyama K. , Misawa H. , Yoshimi N. 
Published: July 2016

AbstractWe have been carrying out solar wind measurements using the interplanetary scintillation (IPS) method. Our IPS observation system is operated at a frequency of 327MHz and consists of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. The present system, however, has insufficient sensitivity to measure enough IPS sources for observing the solar wind with adequate spatial and temporal resolution. Therefore we have been excuting the upgrade project since 1994 in order to observe a larger number of compact radio sources. The Fuji system has been improved successfully and has achieved sensitivity by a factor over five compared with the previous system. The upgrade project is now in progress for the Toyokawa and Sugadaira station.
Objective-Prism Emission-Line Searches for Active Galactic Nuclei
Authors: Gronwall Caryl , Sarajedini Vicki L. , Salzer John J. 
Published: July 2016

AbstractObjective-prism surveys for UV-excess and emission-line objects, especially the First and Second Byurakan Surveys, have been central to the study of active galactic nuclei (AGNs). We review previous line-selected surveys for AGNs and discuss their contribution to our understanding of the AGN phenomena. In addition, we present results from the KPNO International Spectroscopic Survey, a modern digital objective-prism survey for emission line objects. This survey is discovering substantial numbers of new AGNs, in particular low-luminosity AGNs and LINERs.
Comparison of ELG and UV Galaxies from the SBS Survey
Authors: Gyulzadian M. V. 
Published: July 2016

AbstractIn this paper we compare the results of spectrophotometric observations for more then 40 emission line galaxies (ELG) without UV-excess and 70 galaxies with UV-excess (UV-galaxies) from the Second Byurakan Survey (SBS) carried out with the scanner on the 6-m telescope of the Special Astrophysical Observatory. The comparison was aimed to answer the questions: are there any essential differences between these two types of galaxies? And what is the fraction of AGN among ELG and UV-galaxies? To answer this question we have investigated some physical parameters. Great care was taken in classifying the spectra of these galaxies as “HII region-like or “AGN-like” using a new diagnostic method for emission-line galaxies (Rola et al.). We find that 14% of emission line galaxies (ELG) have Sy2 and LINER-like spectra. The transition or ambiguous objects among them comprise 20%. The fraction of LINER-like and Sy2 objects among UV-galaxies is 21% while that of the transition or ambiguous objects in UV-galaxies is 28%. From SBS galaxies, 18% are Sy2s and LINER-like galaxies.
Properties of the Low-z NELGs from the VPM Survey
Authors: Meusinger Helmut , Brunzendorf Jens 
Published: July 2016

AbstractWe discuss the properties of the low-redshift narrow-emission line galaxies detected in the framework of a variability-and-proper motion (VPM) search for AGNs. The VPM-NELG sample is obviously not a random selection of normal field galaxies.
Spectroscopic Diagnostics for AGNs
Authors: Veilleux Sylvain 
Published: July 2016

AbstractA review of the spectroscopic tools needed to characterize AGNs is presented. This review focusses on ultraviolet, optical and infrared emission-line diagnostics specifically designed to help differentiate AGNs from starburst-dominated galaxies. The strengths and weaknesses of these methods are discussed in the context of on-going and future AGN surveys.