Hα Spectral Line Research Articles

Balmer Hα, Hβ and Hγ Spectral Lines Intensities in High-Power RF Hydrogen Plasmas

Hα (Balmer-alpha), Hβ (Balmer-beta) and Hγ (Balmer-gamma) spectral line intensities in atomic hydrogen plasma are investigated by using a high-power RF source. The intensities of the Hα, Hβ and Hγ spectral lines are detected by increasing the input power (0–6 kW) of ICPs (inductively coupled plasmas). With the increase of net input power, the intensity of Hα improves rapidly (0–2 kW), and then reaches its dynamic equilibrium; the intensities of Hβ can be divided into three processes: obvious increase (0–2 kW), rapid increase (2–4 kW), almost constant (4–6 kW); while the intensities of Hγ increase very slowly. The energy levels of the excited hydrogen atoms and the splitting energy levels produced by an obvious Stark effect play an important role in the results.

A system for near real-time detection of filament eruptions at Kanzelhöhe Observatory

AbstractKanzelhöhe Observatory (kso.ac.at) performs regular high-cadence full-disk observations of the solar chromosphere in the Hα and CaIIK spectral lines as well as the solar photosphere in white-light. In the frame of ESA's Space Situational Awareness (SSA) activities, a new system for near real-time Hα image provision through the SSA Space Weather (SWE) portal (swe.ssa.esa.int) and for automatic alerting of flares and erupting filaments is under development. Image segmentation algorithms, based on optical flow image registration, for the automatic detection of solar filaments in real time Hα images have been developed and implemented at the Kanzelhöhe observing system. We present first results of this system with respect to the automatic recognition and segmentation of filaments and filament eruptions on the Sun.

Connection Between Chromospheric Events and Photospheric Dynamics

We analyzed chromospheric events and their connection to oscillation phenomena and photospheric dynamics. The observations were done with the New Solar Telescope of Big Bear Solar Observatory using a broad-band imager at the wavelength of a TiO band and FISS spectrograph scanning Ca ii and Hα spectral lines. The event in Ca ii showed strong plasma flows and propagating waves in the chromosphere. The movement of the footpoints of flux tubes in the photosphere indicated flux tube entanglement and magnetic reconnection as a possible cause of the observed brightening and waves propagating in the chromosphere. An upward propagating train of waves was observed at the site of the downflow event in Hα. There was no clear relationship between photospheric waves and the Ca ii and Hα events. Our observations indicate that chromospheric waves that were previously thought to originate from the photosphere may be generated by some events in the chromosphere as well.

Gas, dust and star formation in nearby galaxies as seen with the JCMT

We presented results using the Nearby Galaxies Legacy Survey (NGLS), which is being carried out with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea in Hawai'i. We have obtained CO J=3−2 data for 155 nearby galaxies to trace the dense molecular gas in which stars are believed to be born. The sample of this survey covers a wide morphological range and has been selected to include galaxies that have been thoroughly studied in the literature, and for which abundant observational data are available. In parallel, we have observed the same sample of galaxies using the Hα spectral line, which traces massive star formation.

Precise effective temperatures of solar analog stars

AbstractWe perform a study of 62 solar analog stars to compute their effective temperatures (Teff) using the Balmer line wing fitting procedure and compare them with Teff values obtained using other commonly employed methods. We use observed Hα spectral lines and a fine grid of theoretical LTE model spectra calculated with the best available atomic data and most recent quantum theory. Our spectroscopic data are of very high quality and have been carefully normalized to recover the proper shape of the Hα line profile. We obtain Teff values with internal errors of about 25K. Comparison of our results with those from other methods shows reasonably good agreement. Then, combining Teff values obtained from four independent techniques, we are able to determine final Teff values with errors of about 10K.

The Peculiar Magnetic Field Morphology of the White Dwarf WD 1953−011: Evidence for a Large‐Scale Magnetic Flux Tube?

We present and interpret new spectropolarimetric observations of the magnetic white dwarf WD 1953–011. Circular polarization and intensity spectra of the Hα spectral line demonstrate the presence of two-component magnetic field in the photosphere of this star. The geometry consists of a weak, large-scale component, and a strong, localized component. Analyzing the rotationally modulated low-field component, we establish a rotation period -->Prot = 1.4480 ± 0.0001 days. Modeling the measured magnetic observables, we find that the low-field component can be described by the superposition of a dipole and quadrupole. According to the best-fit model, the inclination of the stellar rotation axis with respect to the line of sight is -->i ≈ 20°, and the angle between the rotation axis and the dipolar axis is -->β ≈ 10°. The dipole strength at the pole is about 180 kG, and the quadrupolar strength is about 230 kG. These data suggest a fossil origin of the low-field component. In contrast, the strong-field component exhibits a peculiar, localized structure (magnetic spot) that confirms the conclusions of Maxted and coworkers. The mean field modulus of the spot ( -->|Bspot| = 520 ± 7 kG) together with its variable longitudinal magnetic field having a maximum of about +400 kG make it difficult to describe it naturally as a high-order component of the star's global poloidal field. Instead, we suggest that the observed strong-field region has a geometry similar to a magnetic flux tube.

TRANS4: a new coupled electron/proton transport code – comparison to observations above Svalbard using ESR, DMSP and optical measurements

Abstract. We present for the first time a numerical kinetic/fluid code for the ionosphere coupling proton and electron effects. It solves the fluid transport equations up to the eighth moment, and the kinetic equations for suprathermal particles. Its new feature is that for the latter, both electrons and protons are taken into account, while the preceding codes (TRANSCAR) only considered electrons. Thus it is now possible to compute in a single run the electron and ion densities due to proton precipitation. This code is successfully applied to a multi-instrumental data set recorded on 22 January 2004. We make use of measurements from the following set of instruments: the Defence Meteorological Satellite Program (DMSP) F-13 measures the precipitating particle fluxes, the EISCAT Svalbard Radar (ESR) measures the ionospheric parameters, the thermospheric oxygen lines are measured by an all-sky camera and the Hα line is given by an Ebert-Fastie spectrometer located at Ny-Ålesund. We show that the code computes the Hα spectral line profile with an excellent agreement with observations, providing some complementary information on the physical state of the atmosphere. We also show the relative effects of protons and electrons as to the electron densities. Computed electron densities are finally compared to the direct ESR measurements.

Analysis of difference in Hα spectral line profiles between attachment and detachment plasmas in LHD

The sustainable detachment has been achieved in LHD. The line-averaged electron density of the detachment plasmas is typically over 1.0×1020m−3. The difference in the broad component of the Hα spectral line profiles between the attachment and detachment plasmas has been observed. In attachment, the divertor flux much affects the neutral hydrogen generation and the large inward flow up to 1.5×104m/s seemed to be due to the reflection is observed. In detachment, the much smaller flow velocity along the sight lines and the lower Doppler temperature are observed. These observations represent the drastic reduction of the divertor flux and the decrease of the edge electron temperature involved with detachment.

The Lorentz force in atmospheres of CP stars:θ Aurigae

Several dynamical processes may induce considerable electric currents in the atmospheres of magnetic chemically peculiar (CP) stars. The Lorentz force, which results from the interaction between the magnetic field and the induced currents, modifies the atmospheric structure and induces the characteristic rotational variability in the hydrogen Balmer lines. To study this phenomena we have initiated a systematic spectroscopic survey of the Balmer lines variation in magnetic CP stars. In this paper we continue presenting the results of the program, focusing on the high-resolution spectral observations of the A0p star θ Aur (HD 40312). We detected a significant variability in the Hα, Hβ, and Hγ spectral lines during the full rotation cycle of the star. This variability is interpreted in the framework of the model atmosphere analysis, which accounts for the Lorentz force effects. Both the inward- and outward-directed Lorentz forces are considered under the assumption of the axisymmetric dipole or dipole+quadrupole magnetic field configurations. We demonstrate that only the model with the outwardly directed Lorentz force in the dipole+quadrupole configuration is able to reproduce the observed hydrogen-line variation. These results present new strong evidence of non-zero global electric currents in the atmosphere of an early-type magnetic star.

The nuclear ring in the unbarred galaxy NGC 278: Result of a minor merger?

We present fully sampled high angular resolution two-dimensional kinematics in the Hα spectral line, optical and near-infrared imaging, as well as 21 cm atomic hydrogen data of the spiral galaxy NGC 278. This is a small non-barred galaxy, which has a bright star forming inner region of about 2 kpc in diameter, reminiscent of nuclear rings seen mainly in barred galaxies. The Hα kinematics show a disturbed velocity field, which may be partly the result of spiral density wave streaming motions. The 21 cm data trace the atomic hydrogen well outside the optical disk. The H  is not abundant but clearly shows disturbed morphology and kinematics. We postulate that the current structure of NGC 278 is a result of a recent interaction with a small gas-rich galaxy, which is now dispersed into the outer disk of NGC 278. Non-axisymmetries set up in the disk by this minor merger may well be the cause of the intense star formation in the inner region, which can be interpreted as a rare example of a nuclear ring in a non-barred galaxy. Rather than being induced by a bar, this nuclear ring would then be the direct result of an interaction event in the recent history of the galaxy.

Spectroscopy of a ferroelectric plasma cathode

Results of spectroscopic investigations of the plasma formed on the surface of a ferroelectric cathode upon the application of a driving pulse are presented. The ferroelectric plasma cathode was made of a solid solution of Sr, Ba, Ti, Nb, Pb, and O. Its front side was covered by Cu grounded strip electrodes. A driving pulse with an amplitude ≲18 kV and pulse duration of ∼400 ns was applied to the rear Cu disk electrode. A Jobin-Yvon 750M spectrometer was used for visible light dispersion. Spectral line profiles were obtained by a fast framing camera. It was shown that light is emitted from the excited ions and neutral atoms of Cu, Pb, Sr, Ba, Ti, and H within the first 50 ns after the beginning of the driving pulse. By analyzing the Doppler broadening of the observed spectral line profiles it was found that the ion and neutral atom temperature is ⩽0.8 eV. Analysis of the Stark broadening of the Hα and Hβ spectral lines showed the absence of a high (>1 kV/cm) electric field which could be developed at the surface of the ferroelectric due to the appearance of noncompensated surface polarization charges. The same Stark analysis also showed that the plasma density does not exceed 1013 cm−3. By comparing the relative intensities of the Hα and Hβ spectral lines obtained with the results of collision radiative modeling, the plasma electron temperature was found to be ∼3 eV.

Determination of the plasma density in a current sheet from the profiles of the HeII 6560-Å and Hα spectral lines

The electron density in the midplane of a current sheet and far from it is determined from an analysis of the profiles of the HeII 6560-A and Hα spectral lines. A new approach to calculating the Stark broadening of the HeII 6560-A line is developed. The results obtained can be used to determine the plasma density in other experimental devices.

Measurement of angular divergence and ion species ratios of an rf-driven multicusp ion source for diagnostic neutral beam by Doppler shift spectroscopy

The ion species ratios as well as the angular divergences are measured by using a Doppler shift spectroscopy of Hα spectral lines, which originate from several different ions, such as H2+ and H3+ as well as H+, and are spectrally well resolvable from each other on the measured spectral window of detection system. The angular divergences of the ion beam components are determined from the linewidths of the measured emission lines, and the ratio of mixed species is deduced from the intensity ratio of each peak. The ion species ratios measured by the Doppler shift spectroscopy are cross checked by a mass analyzing magnet. The measurements are performed varying the input rf power and the operating source pressure.

Spectroscopic measurements of hydrogen ion temperature during divertor recombination

We explore the possibility of using the neutral Hα spectral line profile to measure the ion temperature, Ti, in a recombining plasma. Since the Hα emissions due to recombination are larger than those due to other mechanisms, interference from nonrecombining regions contributing to the chord integrated data is insignificant. A Doppler and Stark broadened Hα spectrum is simulated by the DEGAS 2 neutral transport code using assumed plasma conditions. The application of a simple fitting procedure to this spectrum yields an electron density, ne, and Ti consistent with the assumed plasma parameters if the spectrum is dominated by recombination from a region of modest ne variation. General measurements of the ion temperature by Hα spectroscopy appear feasible within the context of a model for the entire divertor plasma.

The kinematics of the ionized gas in the Circinus galaxy

The TAURUS-2 Fabry–Perot interferometer, mounted on the 3.9-m Anglo-Australian Telescope, has been used to observe the Circinus galaxy. We have mapped the intensity and velocity distribution of the ionized hydrogen in the galaxy using the Balmer series Hα spectral line. The semiresolved core (observed with a seeing disc of 30 pc) appears amorphous in shape, which is commonly observed in Seyfert 2 galaxies. Its peak coincides with the core position measured in the radio continuum, suggesting that ionized gas surrounds a non-thermal source. A circumnuclear ring or spiral of radius 220 pc and a rotational velocity of 350 km s−1 (assuming circular motions) surrounds the core. The inclination angle of this feature, i=40°±10°, is less than that of the previously observed radio continuum disc. The velocity channel maps obtained for the Hα ring show that the kinematics resemble those of a rotating ring and the intensity displays a complex structure indicative of several, unresolved, H II regions. We believe the ring to represent a circumnuclear starburst. Our Hα data also show the presence of the previously detected [O III] ionization cone to the north-west of the core, measuring more than 400 pc in length. We suggest that the ionization cone lies in a different plane from that of the starburst ring and is directed away from us. Several kinematic components of the core are derived and we calculate an outflow velocity in excess of 150–200 km s−1 for gas above the core of Circinus. We also present evidence for inflowing ionized gas at the centre of Circinus. The correlation of the Hα and radio continuum features is discussed, as well as the possible presence of a starburst-driven superwind in the Circinus galaxy.

Relationships between Galactic Radio Continuum and HαEmission

AbstractRadio continuum emission due to thermal bremsstrahlung and optical Hαspectral line emission arise from processes involving similar atomic entities and physical conditions. The relationship between the flux density of the emission from the two processes is mainly a function of the electron temperature of the emitting region, modified by other factors such as the mode of radiation transfer in the hydrogen spectrum. On the other hand, radio continuum radiation due to non-thermal synchrotron emission is formed by species and processes not involved in thermal emission. As a consequence, differences between the observed radio continuum emission and Hαemission from cosmic sources can provide reliable information on a variety of important physical aspects of the sources, including the relative importance of thermal and non-thermal radio emission and the degree of optical obscuration. This paper reviews the theory of the formation of Hαand the radio continuum in the interstellar medium (ISM), discusses some of the factors that must be considered in comparing observations made in the two frequency regimes, and summarises the properties of some classes of galactic object that emit both optical and radio radiation.

Modelling the Structure of the Ringed Spiral NGC 4736

AbstractWe studied the ringed RSab(r)-type spiral NGC 4736, which has a probably slightly oval disk and a very small bar. We mapped the galaxy in the HI and Hα spectral lines and we obtained long-slit optical spectra. These data were modeled using a 2-D gas dynamical code. The 2-D potential used is axisymmetric in the inner and outer regions and oval (b/a=0.8) at intermediate radii only. The oval component rotates at a pattern speed of 40 km s–1 kpc–1, close to the observed value. Inner and outer rings, like those observed, form at the inner and outer Lindblad resonances, though they co-exist only during a limited time interval in the simulations. The morphology and kinematics of the inner ring and spiral structure as observed in neutral and ionized hydrogen can be well understood in terms of gas dynamical simulations, given the form of the (stellar) potential. What remains to be explained is the origin of the nonaxisymmetric features in the mass distribution defining the potential.

The electron cyclotron resonance heating experiments on HL-1 tokamak

The electron cyclotron resonance heating (ECRH) experiments on HL-1 tokamak with 300 kW of power generated by a gyrotron are described. With ECE diagnostics, a 30% increase of electron temperature has been obtained. The following phenomena have been observed with various diagnostics during ECRH: increase of radiation intensity of soft x-ray; amplitude change and period elongation of sawtooth oscillation; MHD instability suppression; increase of Hα spectral line intensity and ionized impurity radiation from edge plasma; increase of the temperature and density of edge plasma. Although the total plasma energy content increases, the energy confinement time is decreased. Initial results of low voltage start-up experiments have also been obtained.

Determination of the Electron Density in an Argon Laser Plasma by Spectroscopy of the Hydrogen Hα and Hβ Lines

AbstractFrom measurements of the Hα and Hβ spectral line profiles in a plasma, a method is developed which allows to separate the contributions of Doppler and Stark broadening. This method is superior to the deconvolution of Voigt profiles, in particular, when the lines are of low intensity. The electron density in the plasma can be calculated from the Stark broadening.An example is the low pressure (p ≈ 1 hPa) arc discharge of argon ion lasers which is characteristised by electron densities of approximately 1014 cm−3 at heavy particle temperatures of about 104 K. These plasma parameters lead to a broadening of the Balmer Hα and Hβ spectral lines of hydrogen, which has a low concentration within the discharge area. The spectral lines are broadened due to the electron density dependent Stark effect and the temperature responsive Doppler effect. The results are consistent with predictions of the argon ion laser modelling.

Diurnal variation of the linear polarization across the H? and H? Fraunhofer lines of the terrestrial atmosphere, and a detection of a ?daylight flash?, II

In Paper I, the ability of using the polarimetric technique to observe the filling-in of the Fraunhofer spectrum line profiles—the Ring effect—has been presented (using the Hβ Fraunhofer line only). It has also been found that the added light, which caused the filling-in, is polarized. Here, a description is given of some observations, which, hopefully, will lead to a better understanding of the Ring effect using the Hα and Hβ Fraunhofer spectral lines. The observations of the filling-in effect at the zenith have covered many conditions which might be considered as controlling its behaviour at these two spectral regions. The data reveal variations of polarization at the centres of those Fraunhofer lines as a function of solar zenith angle. The results show no uniformity for the added light intensity, its value was depending on the kind of day (clear and turbid) and/or on the solar zenith angle. Also the photometric observational studies reported here suggest that a new phenomenon behaving like airglow has been discovered. It is referred to here as a ‘daylight flash’ and was recorded (for short periods) on three days at both the Hα and Hβ Fraunhofer lines with different strengths. The cores of these lines were filled in while the near continua were unaffected.