bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations of X-Ray Jets Using Yohkoh Soft X-Ray Telescope
Authors: Shibata K. , Ishido Y. , Acton L. , Strong K. , Hirayama T. , Uchida Y. , Mcallister A. , Matsumoto R. , Tsuneta S. , Shimizu T. , Hara H. , Sakurai T. , Ichimoto K. , Nishino Y. , Ogawara Y. 
Published: July 2016

AbstractTime series of SXT (Soft X-ray Telescope) images have revealed many jet-like features in the solar corona. Typical size of the “jet” is 5 × 103 – 4 × 105 km, the typical projected velocity is 30 – 300 km/s, and the kinetic energy estimated to be 1025 – 1028 erg. Many of the jets are associated with flare-like bright points or sub-flares. Three typical examples are discussed, including an X-ray jet identified with an Hα surge. It is suggested that magnetic reconnection is one of the possible mechanisms to produce these X-ray jets.
Statistical Characteristics of Solar Proton Flares
Authors: Wang Jia-Long 
Published: July 2016

AbstractAn investigation of the statistical behaviour of solar flares responsible for the proton events detected at the earth orbit would be of significance for solar physics and sun-earth research. Based on the data given by Kunches (1992) and other relevant data, we study the statistical behaviour of solar proton flares. The asymmetry of distributions, special property of hard X-ray bursts and relation to the large scale mean magnetic field of the proton flares are given in this paper.
A Statistical Study of Flares as Self-Organized Critical Phenomena
Authors: Nakagawa Yoshinari 
Published: July 2016

AbstractThe statistical property of flares is examined in terms of the number of flares versus its magnitude, i. e. the “Importance” reported in the IAU Quarterly Bulletin of Solar Activity for 1961–1983. It is shown that the number of flare and its magnitude follow a power law relationship indicative of the self-organized critical phenomenon, regardless of the phase of the solar cycle.
Solar Flares in Centers of Activity with No Spots
Authors: Šeršeň Michal 
Published: July 2016

AbstractThis paper presents a study of 9 “spotless” flares of H-alpha importance 1 or more which occurred in the years 1981-1990. The flares occurred in positions where no active region has been reported. All the flares were found to occur in evident and well-localized plages, large and diffusive plages as well as in regions where no plage was observed. Only one of all the flares studied in the paper was reported to be accompanied by the filament activity.
Nonlinear Mode Coupling of Resistive Instability and the Flares of February 4 and 6, 1986
Authors: Deng X.H. , Wang S. 
Published: July 2016

AbstractIn this paper, we propose a mechanism of solar flare based on the 3-D nonlinear mode coupling of resistive tearing instability. The results show that the nonlinear coupling of tearing modes leads the rapid destabilization of some high modes. Furthermore, tearing mode turbulence is formed and anomalous resistivity is produced, which in turn, quickens the development of tearing instability and accelerate the magnetic reconnection process. It is suggested that the fast magnetic reconnection as a mechanism of solar flare may be associated with this self-excited process caused by the nonlinear mode coupling of tearing instability in the solar corona. Using our model, we successfully explain all the main typical characters of the flares of February 4 and 6, 1986.
Calcium K-Line Profiles as a Function of Latitude and Solar Cycle Phase
Authors: Singh Jagdev 
Published: July 2016

AstractHigh resolution spectra are being taken in ionized calcium K-line at different latitudes and integrated over the visible 180 degree longitude. These have been analysed to study the variability of the line parameters as a function of latitude. These spectra are being obtained on a regular basis and large data base will be used to study chromospheric rotation, differential rotation in chromosphere, activity and variability of K-line parameters as function of latitude and solar cycle phase. Further, an optical arrangement has been worked out to obtain the spectra along the latitudes of the solar image in the light integrated over longitudes. This involves the unidirectionally focusing of the image in N-S direction.
Magnetic Field Topology in Solar Active Regions
Authors: Seehafer N. 
Published: July 2016

AbstractIn solar active regions, over extended periods of time the plasma-magnetic field configuration evolves quasistatically through a sequence of nearly force-free equilibrium states. This evolution may be understood as the continual distortion of an existing equilibrium by wavelike disturbances propagating upward from the photosphere and subsequent fast relaxation to a new, neighbouring equilibrium. In the present paper the build-up of magnetic energy, which is presumably necessary for flares and other explosive events, during a quasistatic evolution is considered. If during the slow evolution the magnetic energy is increased, then the relaxation processes represent inverse cascades of energy. We study the conditions under which such cascades are possible within the framework of mean-field MHD. In contrast to the convection zone, where the dynamo for the global magnetic field of the Sun works, the solar atmosphere is convectively stable and the first order smoothing approximation justified. It turns out then that current helicity (B.∇ × B) is an important quantity decisive for whether magnetic energy can be built up.
Effect of Sheared Flow on Resistive Tearing Instability and the Triggering of Flare
Authors: Deng X.H. , Wang S. , Chen J.M. , Zhang H.Q. , Ai G.X. 
Published: July 2016

AbstractThe nonlinear evolution of tearing modes in the presence of sheared mass flow is studied in the cylindrical geometry. It is demonstrated that a sufficient large sheared mass flow can destabilize the development of resistive tearing instability. It is suggested that the coupling of sheared mass flow with shear magnetic field may be a triggering of solar flares.
Hα Surge Activity at the First Stage of Magnetic Flux Emergence
Authors: Kurokawa Hiroki , Kawai Goro 
Published: July 2016

AbstractWe present a new observational evidence of the magnetic field reconnection in emerging flux regions (EFR). Our observations show that Hα surges are the first active manifestation of emerging magnetic field in some EFRs. We call them EFR-surges. Examining their morphological and evolutionary characteristics, we conclude that they are produced by the magnetic field reconnection between the EFR and the pre-existing surrounding region.
Coronal Transients in Radio and X-rays
Authors: Kundu Mukul R. 
Published: July 2016

AbstractWe present a summary of several studies of transient coronal phenomena based upon high spatial resolution radio imaging data along with Yohkoh SXT and HXT observations. In addition to normal flares the studies also involve such exotic events as active region transient brightenings (ARTB) and coronal jets and bright points. We provide evidence of nonthermal processes in flaring X-ray bright points from spatially resolved meter-wave data, existence and propagation of type III burst emitting electrons in coronal jets, radio signatures of ARTB’s, and beaming of electrons producing microwave and hard X-rays. The implications of these observations are discussed.
Disconnection of Coronal Field Lines Due to the Emergence of New Photo-Spheric Flux as the Cause of CMES & Interplanetary Shocks
Authors: Bravo S. 
Published: July 2016

AbstractA scenario is presented whereby CMEs and interplanetary shocks are consequences of a large scale rearrangement of the coronal magnetic field induced by the disconnection of field lines from the solar surface due to the emergence of flux with opposite polarity. In this scenario the CME is the mass released from the previously closed structure and the interplanetary shock is formed by the injection of faster solar wind from an extended or newly created coronal hole which results from the opening of the field lines. Here CMEs and interplanetary shocks are associated events, but not cause-effect related. Observational and computational evidence supporting this view is provided.
Numerical Boundary Conditions for Solar Magnetic Hydrodynamic Flows Using the Method of Characteristics
Authors: Wu S. T. , Wang A. H. , Guo W. P. 
Published: July 2016

AbstractWe discuss the self-consistent time-dependent numerical boundary conditions on the basis of theory of characteristics for magnetohydrodynamics (MHD) simulations of solar plasma flows. The importance of using self-consistent boundary conditions is demonstrated by using an example of modeling coronal dynamic structures. This example demonstrates that the self-consistent boundary conditions assure the correctness of the numerical solutions. Otherwise, erroneous numerical solutions will appear.
On the Out of Phase Appearance of Large-Scale Diffuse Magnetic Field of the Sun with Respect to Sunspots
Authors: Dikpati Mausumi , Choudhuri Arnab Rai 
Published: July 2016

AbstractWe assume the large-scale diffuse magnetic field of the Sun to originate from the poloidal component of a dynamo operating at the base of the convection zone, whereas the sunspots are due to the toroidal component. The evolution of the poloidal component is studied to model the poleward migration of the diffuse field seen on the solar surface and the polar reversal at the time of sunspot maxima (Dikpati and Choudhuri 1994, 1995).
Detection of Langmuir Solitons: Implications for Type III Burst Emission Mechanisms at 2ωPE
Authors: Thejappa G. , Stone R.G. , Goldstein M.L. 
Published: July 2016

AbstractWe present the experimental verification of existing theoretical models of emission mechanisms of solar type III bursts at the second harmonic of the plasma frequency, ωpe. This study is based on the detection of Langmuir and envelope solitons by the Ulysses spacecraft inside three type III burst source regions. We show that the oscillating-two-stream instability, coherent radiation by Langmuir solitons and stochastic phase mixing of the Langmuir waves in the strong turbulence regime are the appropriate emission mechanisms at 2ωpe.
Solar Particles Seen by Ulysses Near 33°S
Authors: Tappin S.J. , Simnett G.M. 
Published: July 2016

AbstractObservations of a particle event (electrons >40 keV; ions >50 keV) at heliographic mid-latitudes are presented. The particles are shown to originate from an apparently insignificant solar source and to be stored prior to release into the solar wind.
A New MIR/submm Diagnostic for Dust-Enshrouded AGN
Authors: Haas Martin 
Published: July 2016

AbstractWe show that the PAH 7.7μm to continuum 850μm flux ratio can be used to reveal high mid-infrared extinction in ultraluminous infrared galaxies (ULIRGs). While the submm radiation is optically thin and represents the emission from essentially all dust grains, the PAH strength (measured by the peak height of the Polycyclic Aromatic Hydocarbonates at 7.7μm) is sensitive to dust extinction in the mid-infrared (MIR). As an application of the new diagnostic, after dereddening of the central MIR continuum and with the assumption of a disk-like dust distribution seen under a tilted angle, we find increasing evidence for a hidden quasar in the archetypal ULIRG Arp220.
Surveys of Parsec-scale Radio Structures in AGN
Authors: Gurvits L.I. 
Published: July 2016

AbstractSeveral recent global and Space VLBI surveys of quasars and other types of AGN provide a wealth of material on milli- and sub-milliarcsecond radio structures in hundreds of sources. Results of these projects are presented with an emphasis on the statistics of redshift- and angular-scale-dependent properties of the milli- and sub-milliarcsecond radio structures. These studies make possible disentanglement of intrinsic (possibly, evolutionary) phenomena of parsec-scale radio structures and the imprints of the cosmological model.
Radio AGN Surveys
Authors: De Breuck Carlos , van Breugel Wil , Röttgering Huub , Carilli Chris 
Published: July 2016

AbstractWe present a short overview of radio surveys for AGN, including the ‘complete’ flux limited surveys and ‘filtered’ surveys. We also describe our ultra-steep spectrum search for the highest redshift radio galaxies, and our follow-up VLA and ATCA observations of the most distant (z = 5.19) and the most luminous z <2 radio galaxy known.
Helical Structures in Seyfert Galaxies
Authors: Moiseev A. V. , Afanasiev V. L. , Dodonov S. N. , Mustsevoi V. V. , Khrapov S. S. 
Published: July 2016

Abstract Seyfert galaxies with Z-shaped emission filaments in the Narrow Line Region (NLR) are considered. We assume that observable Z-shaped structures and the velocity pattern of the NLR may be explained as tri-dimensional helical waves in the ionization cone.
Correlation of Optical and X-ray Radiation of NGC 4151 and 3C 390.3. Preliminary Results
Authors: Novikova Olga A. , Bochkarev Nikolai G. 
Published: July 2016

AbstractThe correlation of optical and X-ray radiation of some AGN is studied. We used low signal-to-noise data from the All-Sky Monitor of the Rossi X-ray Timing Explorer (2-10 KeV) and broad-band photometry of the optical continuum obtained mainly during the last several years through the "AGN Watch" program.
The evolution of the Kuiper belt during the formation of the outer planets
Authors: Melita M.D. , Brunini A. 
Published: July 2016

AbstractA self-consistent study of the formation of planetary bodies beyond the orbit of Saturn and the evolution of Kuiper disks is carried out by means of an N-body code where accretion and gravitational encounters are considered. This investigation is focused on the aggregation of massive bodies in the outer planetary region and on the consequences of such process in the corresponding cometary belt. We study the link between the bombardment of massive bodies and mass depletion and eccentricity excitation.
The long term evolution of Atens and Apollos
Authors: Dvorak R. 
Published: July 2016

AbstractIn this review we report on the investigations of the long term dynamics of the Near Earth Asteroids (NEAs). In the first part some theoretical results concerning the dynamical structure of the NEA belt are explained. We then present our knowledge of the long term evolution of the orbits of NEAs for time intervals up to several million years which were derived by extensive numerical integrations. An interesting point of investigation is the steady flux from the Atens to the Apollos and vice-versa which is caused primarily by close encounters with the Earth and Venus. We also report the results concerning the probability of collisions of the NEAs with these planets. Finally the possible capture of such objects into Trojan-like orbits − thus moving in a 1:1 resonance with one of the inner planets − is discussed.
Veritas family age revisited
Authors: Knežević Z. 
Published: July 2016

AbstractA progess report is given for the project of redetermination of the estimate of an upper limit to the age of the Veritas asteroid family, derived originally by Milani and Farinella (1994). The results obtained so far are consistent with the conjecture of a young age of this family (&lt; 100 Myr).
How many binaries are there among near-Earth asteroids?
Authors: Pravec P. , Wolf M. , Šarounová L. 
Published: July 2016

AbstractThe near-Earth asteroids 1991 VH, 1994 AW1and (3671) Dionysus have been identified as binary systems. They are similar each to other in some of their characteristics. This leads us to a suggestion that there is present a similar mechanism of their creation and/or evolution and that there exists a sizeable population of binaries among NEAs. From a simple geometric model, we estimate that a probability that a binary system with the characteristics similar to the three binaries contains signs of occultation/eclipse phenomena in its lightcurve (thus allowing a detection of the binarity) in particular geometric conditions ispocc~0.30. Then, the actual number of binary NEAs present in a studied sample of NEAs isN =10+8-5. Since the studied sample of NEAs contains effectively 59 objects, we estimate that ∼ 17% of NEAs are binary, this value is uncertain by a factor 2, however.
Brightness of long-period comets at large heliocentric distances: II. The computer catalogue for 1945-1957
Authors: Svoreň J. 
Published: July 2016

AbstractThe paper is a compilation of more than 3500 magnitude estimates of 20 long-period comets observed at the heliocentric distances larger than 2.5 AU with the well determined orbits which passed the perihelion from 1945 to 1957. This is the second part of the catalogue of long-period comets. The first part (covering 1861-1941) was published in the Planet. Space Sci. The compilation is continuing up to date and after finishing it will be a supplement to the short-period CLICC/A catalogue compiled by Kamél and ICQ archive compiled by Greenet al.The list contains dates of observations, apparent brightness of the comets and the types of magnitudes, methods, diameters of objectives and the light-gathering powers of the telescope used, types of instruments, names of observers and references to the original literature as well as the calculated values of the heliocentric and geocentric distances and phase angles. The collected brightness data formed a basis for study systematic corrections among various observers, instruments and methods, for construction of photometric curves, perihelion asymmetry study, calculation of dimensions of cometary nuclei, study of interrelations between dynamical and physical parameters, and many others. The catalogue exists only in computer version and can be obtained from the author by e-mail.
What happened with the comet 71P/Clark?
Authors: Szutowicz S. 
Published: July 2016

AbstractDiscovered in 1973, 71P/Clark had made only five revolutions around the Sun. The motion of the comet has been subjected to a constant small deceleration between 1973 and 1989 and then a dramatic jump in the nongravitational perturbations occured. To explain the discontinuity in the comet's nongravitational effects a change in the surface distribution of active areas and a nucleus orientation was considered. The model of discrete source of out gassing was employed in the orbital calculations. From numerical fitting of the model parameters to positional observations the spin-axis orientation, localizations and outgassing areas of two active regions have been derived and the orbit successfully improved. The nucleus radius was estimated as equal to 0.76 km.
The gravity influence of the regular and irregular Galaxy field on the stability of the Oort cloud
Authors: Chujkova N.A. , Nagoga M.A. , Maximova T.G. 
Published: July 2016

AbstractThe problem of the determination of the tidal influence of the Galaxy gravity field on the equilibrium of the Solar system boundary zone is investigated. The coordinates of regions with maximum time and space variations of the tidal influence are determined. These regions may be the possible sources of young comets. The frequencies of the periodical movements of the Solar system, caused by both the total Galaxy gravity field and the internal field of the nearest stars, are determined. The hypothesis explaining the coincidence of the periods of the Solar system oscillation and the geodynamic activity by the increase of the comets passing near the Sun-Earth is presented.
Stellar Flare Spectral Diagnotics: Present and Future
Authors: Foing Bernard H. 
Published: July 2016

AbstractStellar spectral diagnostics are of utmost importance to test fundamental concepts of flare physics such as particle beam versus suprathermal heating, atmospheric response, mass motions, microflaring, statistics and recurrence of flares, flare activity and stellar interior. We review some of these diagnostics (from photometry, optical, and ultraviolet spectroscopy at medium- and high-spectral resolution, X-ray, and radio observations). Specific diagnostics from line and continuum fluxes, density sensitive lines, broadening and velocity field effects and the comparison with semi-empirical models are also described.Some results on stellar flares obtained from previous multi-wavelength observing campaigns are presented. Future satellite missions and ground-based observatories, with new techniques for obtaining high spectral and temporal resolution, are discussed in light of their possible contribution to our understanding of solar and stellar flares.
The Role of Eruption in Solar Flares
Authors: Sturrock Peter A. 
Published: July 2016

AbstractThis article focuses on two problems involved in the development of models of solar flares. The first concerns the mechanism responsible for eruptions, such as erupting filaments or coronal mass ejections, that are sometimes involved in the flare process. The concept of ‘loss of equilibrium’ is considered and it is argued that the concept typically arises in thought-experiments that do not represent acceptable physical behavior of the solar atmosphere. It is proposed instead that such eruptions are probably caused by an instability of a plasma configuration. The instability may be purely MHD, or it may combine both MHD and resistive processes. The second problem concerns the mechanism of energy release of the impulsive (or gradual) phase. It is proposed that this phase of flares may be due to current interruption, as was originally proposed by Alfvén and Carlqvist. However, in order for this process to be viable, it seems necessary to change one's ideas about the heating and structure of the corona in ways that are outlined briefly.
Cyclotron Lines in the Spectra of Solar Flares and Solar Active Regions
Authors: Zheleznyakov V. V. , Zlotnik E. Ya. 
Published: July 2016

AbstractIt was shown by Zheleznyakov and Zlotnik (1980a, b) that in complex configurations of solar magnetic fields (in hot loops above the active centres, in neutral current sheets in the preflare phase, in hot X-ray kernels in the initial flare phase) a system of cyclotron lines in the spectrum of microwave radiation is likely to be formed. Such a line was obtained by Willson (1985) in the VLA observations at harmonics of the electron gyrofrequency. This communication interprets these observations on the basis of an active region model in which thermal cyclotron radiation is produced by hot plasma filling the magnetic tube in the corona above a group of spots. In this model the frequency of the recorded 1658 MHz line corresponds to the third harmonic of electron gyrofrequency, which yields the magnetic field (196 + 4) G along the magnetic tube axis. The linewidth Af/f ∼ 0.1 is determined by the 10% inhomogeneity of the magnetic field over the cross-section of the tube; the line profile indicates the kinetic temperature distribution of electrons over the tube cross-section with the maximum value 4 x 106 K. Analysis shows that study of cyclotron lines can serve as an efficient tool for diagnostics of magnetic fields and plasma in the solar active regions and flares.
Computer Control of the Vacuum Solar Telescope
Authors: Dunn Richard B. 
Published: July 2016

The Vacuum Solar Telescope has been described elsewhere by Dunn (1964, 1969). A brief summary of its characteristics is included here as background for discussing the computer control of this instrument.This telescope is altazimuth in design. Image rotation is accomplished by rotating the inner tube structure together with all the auxiliary instruments. Azimuth and elevation torque motors drive the two mirrors at the top of the tower to track the sun automatically. The inputtothe servo is derived from a photoelectric guider. When clouds intervene, the servos are switched from the photoelectric guider to an electromechanical coordinate converter that also generates the signal for the rotation of the table. An elaborate 25: 1 synchro system connects the mirror servos to the coordinate converter.