Wing Intensities Research Articles

Properties of ubiquitous magnetic reconnection events in the lower solar atmosphere

Context.Magnetic reconnection in the deep solar atmosphere can give rise to enhanced emission in the Balmer hydrogen lines, a phenomenon referred to as Ellerman bombs. Recent high-quality Hβobservations indicate that Ellerman bombs are more common than previously thought, and it was estimated that at any time, about half a million Ellerman bombs are present in the quiet Sun.Aims.We performed an extensive statistical characterization of the quiet-Sun Ellerman bombs (QSEBs) in these new Hβobservations.Methods.We analyzed a 1 h dataset of the quiet Sun observed with the Swedish 1-m Solar Telescope that consists of spectral imaging in the Hβand Hαlines as well as spectropolarimetric imaging in Fe I6173 Å. We used thek-means clustering and the 3D connected component labeling techniques to automatically detect QSEBs.Results.We detected a total of 2809 QSEBs. The lifetimes vary between 9 s and 20.5 min, with a median of 1.14 min. The maximum area ranges between 0.0016 and 0.2603 Mm2, with a median of 0.018 Mm2. The maximum brightness in the Hβwing varies between 1.06 and 2.76 with respect to the average wing intensity. A subset (14%) of the QSEBs displays enhancement of the Hβline core. On average, the line core brightening appears 0.88 min after the onset of brightening in the wings, and the distance between these brightenings is 243 km. This gives rise to an apparent propagation speed ranging between −14.3 and +23.5 km s−1, with an average that is upward propagating at +4.4 km s−1. The average orientation is nearly parallel to the limbward direction. QSEBs are nearly uniformly distributed over the field of view, but we find empty areas with the size of mesogranulation. QSEBs are located more frequently near the magnetic network, where they are often larger, live longer, and are brighter.Conclusions.We conclude that QSEBs are ubiquitous in the quiet Sun and appear everywhere, except in areas of mesogranular size with the weakest magnetic fields (BLOS ≲ 50 G). Our observations support the interpretation of reconnection along vertically extended current sheets.

Spectral Characteristics of the He i D3 Line in a Quiescent Prominence Observed by THEMIS

We analyze the observations of a quiescent prominence acquired by the Telescope Heliographique pour l'Etude du Magnetisme et des Instabilites Solaires (THEMIS) in the He I 5876 A (He I D3) multiplet aiming to measure the spectral characteristics of the He I D3 profiles and to find for them an adequate fitting model. The component characteristics of the He I D3 Stokes I profiles are measured by the fitting system approximating them with a double Gaussian. This model yields an He I D3 component peak intensity ratio of $5.5\pm0.4$, which differs from the value of 8 expected in the optically thin limit. Most of the measured Doppler velocities lie in the interval $\pm5$ km/s, with a standard deviation of $\pm1.7$ km/s around the peak value of 0.4 km/s. The wide distribution of the full-width at half maximum has two maxima at 0.25 A and 0.30 A for the He I D3 blue component and two maxima at 0.22 A and 0.31 A for the red component. The width ratio of the components is $1.04\pm0.18$. We show that the double-Gaussian model systematically underestimates the blue wing intensities. To solve this problem, we invoke a two-temperature multi-Gaussian model, consisting of two double-Gaussians, which provides a better representation of He I D3 that is free of the wing intensity deficit. This model suggests temperatures of 11.5 kK and 91 kK, respectively, for the cool and the hot component of the target prominence. The cool and hot components of a typical He I D3 profile have component peak intensity ratios of 6.6 and 8, implying a prominence geometrical width of 17 Mm and an optical thickness of 0.3 for the cool component, while the optical thickness of the hot component is negligible. These prominence parameters seem to be realistic, suggesting the physical adequacy of the multi-Gaussian model with important implications for interpreting He I D3 spectropolarimetry by current inversion codes.

Defect structure of epitaxial layers of III nitrides as determined by analyzing the shape of X-ray diffraction peaks

The shape of X-ray diffraction epitaxial layers with high dislocation densities has been studied experimentally. Measurements with an X-ray diffractometer were performed in double- and triple-crystal setups with both CuK α and MoK α radiation. Epitaxial layers (GaN, AlN, AlGaN, ZnO, etc.) with different degrees of structural perfection grown by various methods on sapphire, silicon, and silicon carbide substrates have been examined. The layer thickness varied in the range of 0.5–30 μm. It has been found that the center part of peaks is well approximated by the Voigt function with different Lorentz fractions, while the wing intensity drops faster and may be represented by a power function (with the index that varies from one structure to another). A well-marked dependence on the ordering of dislocations was observed. The drop in intensity in the majority of structures with a regular system and regular threading dislocations was close to the theoretically predicted law Δθ–3; the intensity in films with a chaotic distribution decreased much faster. The dependence of the peak shape on the order of reflection, the diffraction geometry, and the epitaxial layer thickness was also examined.

Spectral study of a pair of Ellerman bombs

Results of the analysis of spectral observations of two Ellerman bombs in the Hα line are presented. These bombs (EB-1 and EB-2) appeared and evolved in the active region NOAA 11024 in the emerging magnetic flux area. The spectral data of a high temporal and spatial resolution were obtained with the French–Italian solar telescope THEMIS (Tenerife Island, Spain; THEMIS stands for Telescope Heliographique pour l’Etude du Magnetisme et des Instabilites Solaires) on July 4, 2009. The Hα-line profiles obtained for different periods of the Ellerman bombs (EBs) evolution were asymmetrical, demonstrating the emission excess in the long-wavelength wing. The intensity variations in the line wings indicate both the gradual and pulsed release of energy in the course of EBs. Temporal variations in the line-of-sight velocities Vlos of the chromospheric material at a level of the Hα-core formation showed two periods in the velocity enhancement, containing several individual peaks. The maximum line-of-sight velocity of the material was–9 and 8 km/s toward and from the observer, respectively. Rapid upward and downward plasma streams (where Vlos reaches–80 and 50 km/s, respectively) were sometimes observed. The Ellerman bombs were accompanied by small chromospheric ejections (surges) lasting for 0.5–1.5 min. A fine structure of EBs was found in the Hα-line spectra obtained during 4 min, when the intensity in the line wings sharply increased. The peculiarities of variations in the intensity of the Hα-line wings and the line-of-sight velocity of the chromospheric material suggest that two investigated EBs appeared and evolved as a physically connected pair. Our results support the model wherein the magnetic reconnection in the lower atmospheric layers is considered as a triggering mechanism for the EB formation.

Ectoparasites may serve as vectors for the white-nose syndrome fungus.

BackgroundVertebrate ectoparasites frequently play a role in transmission of infectious agents. Pseudogymnoascus destructans is a psychrophilic fungus known to cause white-nose syndrome (WNS), an emerging infectious disease of bats. It is transmitted with direct contact between bats or with contaminated environment. The aim of this study was to examine wing mites from the family Spinturnicidae parasitizing hibernating bats for the presence of P. destructans propagules as another possible transmission route.MethodsWing mites collected from 33 bats at four hibernation sites in the Czech Republic were inspected for the presence and load of pathogen's DNA using quantitative PCR. Simultaneously, wing damage of inspected bats caused by WNS was quantified using ultraviolet light (UV) transillumination and the relationship between fungal load on wing mites and intensity of infection was subjected to correlation analysis.ResultsAll samples of wing mites were positive for the presence of DNA of P. destructans, indicating a high probability of their role in the transmission of the pathogen's propagules between bats.ConclusionsMechanical transport of adhesive P. destructans spores and mycelium fragments on the body of spinturnicid mites is highly feasible. The specialised lifestyle of mites, i.e., living on bat wing membranes, the sites most typically affected by fungal growth, enables pathogen transport. Moreover, P. destructans metabolic traits suggest an ability to grow and sporulate on a range of organic substrates, including insects, which supports the possibility of growth on bat ectoparasites, at least in periods when bats roost in cold environments and enter torpor. In addition to transport of fungal propagules, mites may facilitate entry of fungal hyphae into the epidermis through injuries caused by biting.

Mg ii Lines Observed During the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph

Mg II lines represent one of the strongest emissions from the chromospheric plasma during solar flares. In this article, we studied the Mg II lines observed during the X1 flare on March 29 2014 (SOL2014-03-29T17:48) by IRIS. IRIS detected large intensity enhancements of the Mg II h and k lines, subordinate triplet lines, and several other metallic lines at the flare footpoints during this flare. We have used the advantage of the slit-scanning mode (rastering) of IRIS and performed, for the first time, a detailed analysis of spatial and temporal variations of the spectra. Moreover, we were also able to identify positions of strongest HXR emissions using RHESSI observations and to correlate them with the spatial and temporal evolution of Mg II spectra. The light curves of the Mg II lines increase and peak contemporarily with the HXR emissions but decay more gradually. There are large red asymmetries in the Mg II h and k lines after the flare peak. We see two spatially well separated groups of Mg II line profiles, non-reversed and reversed. In some cases, the Mg II footpoints with reversed profiles are correlated with HXR sources. We show the spatial and temporal behavior of several other line parameters (line metrics) and briefly discuss them. Finally, we have synthesized the Mg II k line using our non-LTE code with the MALI technique. Two kinds of models are considered, the flare model F2 of Machado et al. (1980) and the models of Ricchiazzi and Canfield (1983). Model F2 reproduces the peak intensity of the unreversed Mg II k profile at flare maximum but does not account for high wing intensities. On the other hand, the RC models show the sensitivity of Mg II line intensities to various electron-beam parameters. Our simulations also show that the microturbulence produces a broader line core, while the intense line wings are caused by an enhanced line source function.

Temporal variations in solar magnetic bright points intensity and plasma parameters

Magnetic bright points are one of the finest magnetic structures observed in the solar atmosphere. They possibly represent single flux tubes in quiet Sun regions. Their formation is described by the convective collapse model, while the decay phase of these structures is not well characterized yet. We attempt to follow the evolution of a few selected examples of MBPs and to study their changes in brightness and also the variations of plasma parameters during their lifetime. We use data from the Hinode satellite and the Sunrise mission. The G-band observations taken with a cadence of 30 seconds by the Hinode Solar Optical Telescope (SOT) show very fast changes of the maximum intensity of these structures. The complementary spectropolarimetric data, which are used to estimate the plasma parameters, were taken with a cadence of approximately two minutes. The variations of plasma parameters cannot be matched one to one to the changes in intensity due to the different temporal resolution. However, the slow changes of intensity with large amplitude are matched with variations of magnetic field strength and line-of-sight (LOS) velocity. The Sunrise/IMaX data have a temporal resolution of 32 seconds and show fast variations in the line wing intensity. These variations are associated with changes in the magnetic field strength and LOS velocity.

Elastic collisions of interstellar helium atoms with solar wind protons

Relative motion of the Sun with respect to the surrounding local interstellar medium results in entering of interstellar helium atoms into the heliosphere. Current models of helium flowing into the solar system do not include elastic collisions of atoms with solar wind ions. It was predicted in 1986, without quantitative elaboration, that such collisions would enhance wings of directional distributions of helium atom fluxes. This paper focuses on a theoretical treatment of elastic collisions of interstellar He atoms with the solar wind protons resulting in increased wing intensities, called the helium flux halo in contradistinction to the flux core. We concentrate on directional distributions of He atom intensities at 1 AU from the Sun for observers at rest and moving with the Earth and confirm the formation of the flux halo. We show that the collision‐produced halo would often dominate He atom intensities at angles larger than 30°–35° from the maximum intensity direction in the flux core. A comparison with direct measurements of interstellar helium atom fluxes is beyond the scope of this paper.

Line mixing in Raman scattering spectra of CO2 modelled by a non-Markovian Energy-Corrected Sudden approach

Non-Markovian Energy-Corrected Sudden modelling of room-temperature CO2 Raman scattering spectra up to the far wing is revisited and completed for gas densities between 1 and 45 amagat. The model parameters are fitted on an extended set of low-pressure isolated line widths including very high values of the rotational quantum number J and well reproduce the decreasing of line broadening for the experimentally studied J-values. From calculations of the absolute-intensity rototranslational spectrum at 23 amagat, it is shown that the traditional adiabaticity factor of De Pristo gives a more coherent description of low-pressure line widths and high-pressure wing intensities than the two-parameter factor of Birnbaum–Cohen. A simple qualitative correction of the ECS-modelled intensities for the induced and cross allowed-induced scattering appears to be insufficient to match the experimental data in the spectral wing. Theoretical spectral shapes are also calculated for the O-Q-S branches of vibrotational ν1 and 2ν2 Raman bands and compared to experimental results in the density range 1–45 amagat.

ANALYSIS OF CORONAL GREEN LINE PROFILES: EVIDENCE OF EXCESS BLUESHIFTS

The coronal green line (Fe XIV 5303 A) profiles were obtained from Fabry-Perot interferometric observations of the solar corona during the total solar eclipse of 21 June 2001 from Lusaka, Zambia. The instrumental width is about 0.2 A and the spectral resolution is about 26000. About 300 line profiles were obtained within a radial range of 1.0-1.5 R\odot and position angle coverage of about 240\circ. The line profiles were fitted with single Gaussian and their intensity, Doppler velocity, and line width have been obtained. Also obtained are the centroids of the line profiles which give a measure of line asymmetry. The histograms of Doppler velocity show excess blueshifts while the centroids reveal a pre-dominant blue wing in the line profiles. It has been found that the centroids and the Doppler velocities are highly correlated. This points to the presence of multiple components in the line profiles with an excess of blueshifted components. We have then obtained the(Blue-Red) wing intensity which clearly reveals the second component, majority of which are blueshifted ones. This confirms that the coronal green line profiles often contain multicomponents with excess blueshifts which also depend on the solar activity. The magnitude of the Doppler velocity of the secondary component is in the range 20-40 km s-1 and they show an increase towards poles. The possible explanations of the multicomponents could be the type II spicules which were recently found to have important to the coronal heating or the nascent solar wind flow, but the cause of the blue asymmetry in the coronal lines above the limb remains unclear.

Intermolecular repulsive–dispersive potentials explain properties of impurity spectra in soft solids

Abstract Behavior of optical impurity spectra in van der Waals glasses is rationalized with the aid of a two-particle Lennard–Jones model of intermolecular interactions. Simple mathematical manipulations with the 6–12 potential yield inhomogeneous distribution functions (IDFs) of zero phonon lines (ZPLs) at different compressions, and the expressions for wavelength dependent pressure shift coefficients of ZPLs (or holes), local phonon frequencies, and linear and quadratic coupling constants. Experimentally, the ZPL to phonon wing intensity ratios (Huang–Rhys or Debye–Waller factors) are measured for bacteriochlorophyll a in glass-forming triethylamine 5 K. Enhancement of coupling strength with increasing transition wavelength is observed, in qualitative agreement with the model.

Dynamical processes in the June 26, 1999 flare

The evolutionary and spatial characteristics of the motions in the flaring chromosphere of a 2B/M2.3 flare are investigated by analyzing the asymmetry in the Hα profiles. The possibility of reconciling the results of observations with the theory of chromospheric evaporation is considered. The spectroscopic Hα observations of the flare performed with the KG-2 CrAO coronagraph with a temporal resolution of 5–10 s and a spatial resolution as high as 1 arcsec cover all stages of flare development. The following results have been obtained: (1) The Hα profile asymmetry is a general characteristic of the flare emission irrespective of its intensity and its belonging to different structural features and phases of flare development. (2) Most of the Hα emission profiles in flare regions exhibit a red asymmetry. However, a blue asymmetry was observed in small local regions at all stages of flare development. (3) A red asymmetry that appeared before the onset of the impulsive phase and persisted after its end was observed at the sites of main energy release, i.e., the energy source responsible for the dynamical processes in the flare came into operation earlier and existed longer than the HXR emission. (4) The asymmetry pattern changed with flare phase: the red wing intensity dominated in the pre-impulsive phase and at the onset of the impulsive and gradual phases (while the line core was unshifted or slightly shifted). At the maximum of the impulsive phase, the nearly symmetric profiles with extended wings were redshifted as a whole, i.e., the entire emitting volume moved down with a velocity of several tens of km/s. This type of asymmetry cannot be explained by the dynamical model of chromospheric condensation (Canfield and Gayley 1987). (5) The Hα profiles show no evidence of chromospheric heating by a beam of nonthermal electrons during the impulsive phase (Canfield et al. 1984). (6) The lifetime of the downflows and the change in their velocities with time are inconsistent with the dynamical model of chromospheric condensation (Fisher 1989). (7) The morphological features of the velocity field are also inconsistent with the theory of chromospheric evaporation, because the highest differently directed velocities were detected at the flare loop tops, not at the sites of main energy release. We conclude that the investigated flare shows spectral features that are inconsistent with the standard chromospheric evaporation model.

Excited spectator electron effects on spectral line shapes

Excited spectator electron effects on Stark broadened spectral line shapes of transitions involving tightly bound electrons are investigated. It is shown that the interference terms in the electron impact broadening are essential to describe the overlapping lines generated by these configurations (e.g.; dielectronic satellite lines). The main impact is narrower spectral features and reduced far wing intensities compared to calculations neglecting the interference terms.

The intensity of collision-induced wings of isotropic Raman scattering

The integral intensity of collision-induced wings of isotropic Raman scattering for totally-symmetric vibration has been discussed analytically. The intensity of scattered radiation was considered in the dipole-induced dipole (DID) approach. The radial as well as angular–radial contributions to intensity of scattered radiation were taken into account. Three body radial contribution to integral intensity was evaluated in the Kirkwood superposition approximation. For angular–radial terms we apply B. Ladanyi and T. Keyes' [Mol. Phys., 33 (1977) 1063] approximation, disregarding the “irreducible connected” terms in our formulas describing the integral intensity. For numerical evaluations the Molecular Dynamics (MD) results for the gl 1 l 2 m( r 12) coefficients of the two-body correlation function were used. Analytical formulae were applied numerically to N 2 and CO 2 systems.

Analysis and design of nonlinear fiber Bragg gratings and their application for optical compression of reflected pulses

We demonstrate a novel split-step solution for analyzing nonlinear fiber Bragg gratings. The solution is used for designing nonlinear fiber Bragg gratings with a low reflectivity. The structure of the grating is designed according to the profiles of the incident and reflected pulses. We demonstrate our method for nonlinear compression of a pulse reflected from a fiber Bragg grating. The method allows us to obtain compressed pulses with a very low wing intensity.

Doppler spectroscopy of hydrogen and deuterium balmer alpha line in an abnormal glow discharge

The results of hydrogen and deuterium Balmer alpha line shapes and line intensities study in an abnormal glow discharge are reported and analyzed. The Doppler shifts along line wings are used to determine energies of excited hydrogen and deuterium atoms. For 12 different cathodes, intensity and shape of line wings are examined and dependence upon cathode material is determined. Tentative explanation of line wings intensity dependence is related to the sputtering of cathode material and back-scattering coefficients of incident hydrogen or deuterium ions and atoms from cathode surface. The influence of the light reflected on a cathode surface to the line shape measurements along discharge axis is considered. In hydrogen, deuterium, and Ar+3%H/sub 2/ discharges, basic mechanisms of fast hydrogen generation and excitation are studied. The shape and intensities of the H/sub /spl alpha// line profiles in pure hydrogen and in argon-hydrogen mixture may be correlated with hydrogen atom-carrier gas collision excitation cross sections. In order to assess the importance of reflected fast hydrogen atoms back scattered from the cathode surface, for the Balmer line shape formation, a simulation program is used. The results are in a qualitative agreement with Balmer line shapes observations.

Observation of edge refraction in ultra small angle neutron scattering

Slits and macroscopic objects such as edges give rise to refraction and diffraction. In this Letter we show the effect of Cd edges and slits if they are inserted between the monochromator and analyser in a double crystal diffractometer. Despite to the use of wavelengths of tens of nanometer and strong absorbing materials refraction is observed which contributes to enhanced wing intensity of the instrumental curve of the double crystal diffractometer.

Observation of Edge Diffraction with a Double Crystal Diffractometer

We have observed edge diffraction with a double crystal diffractometer and therefore can explain the enhanced wing intensity of measured Darwin profiles in dynamical diffraction. Precise experiments uniquely demonstrate the contribution of Fresnel diffraction at absorbing straight edges, interpreted as ultra small angle scattering (USAS) or diffuse scattering in other experiments. No contributions were found due to ultra small surface scattering or TDS stemming from the crystals, which was proposed by other groups to explain the enhanced wing intensity of their measured rocking curves.

TT Arietis: Spectroscopy and Photometry

We report the photometry and spectroscopy of TT Arietis around the turn of the millennium, when the nova-like variable is in high state. A positive superhump since 1997 still exists. A more precise orbital period than before, 0:13755040+/-1.7x10(-7) days, is established. The intensity of the Balmer emission core is found to modulate at the superhump period rather than the orbital period and 180degrees out of phase with continuum. The intensity of Balmer absorption wings is approximately proportional to the continuum flux. The correlation between Balmer lines and continuum provides a new clue to the study of sources of continuum and emission lines. The mass ratio of the binary is found to be in the range of 0.19+/-0.04, which lends strong support to the proposition that superhumps arise from the inner Lindblad 3: 1 resonance in TT Ari, as in superoutbursts of SU UMa stars.

Diagnostics of electron bombardment in solar flares from hydrogen Balmer lines

Influence of non-thermal collisional rates, related to an electron beam, on hydrogen Balmer line profiles is investigated. Semi-empirical temperature structure of the flare model F1 has been used for computing non-LTE profiles of Hα, Hβ, and Hγ. Contribution functions and their change due to different values of beam parameters are shown. Unlike the line core intensity, the intensity of line wings considerably depends on beam parameters and it is significantly enhanced for typical values of the beam energy flux. The ratio of line intensities at a selected wavelength is proposed to be used for diagnostics of electron beams during solar flares, particularly at impulsive phases. Obtained Ha line profiles are compared to those of Fang et al. (1993).