Intensity fluctuations in Fraunhofer lines

An expression is derived for the fluctuation (t) in emergent intensity (observed at some wavelength in a Fraunhofer line or the continuum) caused by a perturbation in temperature (z, t) in the Sun's atmosphere. If the contribution function for the observed intensity is single-peaked near z and if (z) and p(z) are not too rapidly varying, then (t) m (z , t)+N p(z , t) where m and N depend on the structure of the atmosphere. We compute M, N, and contribution functions for several values of and in the inner wings of the K line (13933 Caii).Presently on leave of absence from the Institute for Astronomy, Honolulu, Hawaii.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

The influence of a photospheric spectrum of turbulence on the profiles of weak Fraunhofer lines

We assume that the motion field in the solar photosphere is described by a spectrum of turbulence, defined by suitably chosen parameters. For various values of the spectral parameters we compute average (i.e. averaged over a sufficiently large part of the photosphere) profiles of weak Fraunhofer lines. The resulting profiles which represent the distribution function of line-of-sight velocity components as modified by the transfer of radiation through the atmosphere, are thereupon still broadened by a function representing the influence of the distribution function of the granulation cell sizes. The resulting functions should be compared with the distribution function of line-of-sight velocity components as derived from observations, in order to arrive at an observational derivation of the parameters of the photospheric spectrum of turbulence.     

On the asymmetry of selected Fraunhofer lines

An analysis is made of the asymmetry of Fraunhofer lines observed with the double-pass monochromator of the horizontal solar telescope ASU-5 of the Main Astronomical Observatory of the Ukrainian Academy of Sciences. The conclusion is that the character of macromotion in the radial direction varies with height; in a tangential direction the motions at different depths are homogeneous. The asymmetry of weak lines is due to convection rather than to wave motions.     

A search for polarization in radio recombination lines

We have attempted to detect linear polarization in carbon and hydrogen 76 radio recombination lines from the Hii region NGC 2024. The upper limits set by these measurements are briefly discussed.On leave of absence from Cornell University, Ithaca, N.Y., U.S.A.     

Fraunhofer lines with large Zeeman splitting

A list of solar spectral lines having simple Zeeman triplet splitting with Landé g-factors equal to or greater than 2.5 is presented.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

A search for new features in the visible spectrum of Io

The spectrum of Io between 4000 Å and 6000 Å has been studied at high resolution for new features. None were found. The upper limit to new emissions varies with wavelength from 13 kR to 49 kR.     

The observed limb effect in Fraunhofer lines,II

In this paper the absolute limb effect for a number of Fraunhofer lines observed at the McMath Solar Observatory is given. Results, uncorrected for scattered light, are given for the following lines: Fei 37334.9, 3735.3, 5123.7, 5250.2, 5434.5, 6678.0, and 8886.6. Additional lines observed are five lines of CN 3876.3–3880.0, two lines of Cai 6161.3 and 6162.2, one line of Nai, 6160.7, and one CN line (7957.0) of the red system.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.     

The observed limb effect in Fraunhofer lines,I

The absolute limb effect is presented for Fei lines 3767 and 3969; for five Tii lines of multiplet 42 near 4535 and one Tiii line at 4534; two lines of Mgi, 4571 and 5172; two lines of Baii at 5854 and 6497. The scattered light of the McMath solar telescope is illustrated by several figures but not applied to the limb-effect observations. It is suggested that the supergravity shift at the limb is the result of scattering of the atoms in anisotropic velocity field.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.     

A first order analysis of variations of the limb darkening and the shapes for solar Fraunhofer lines

New center-to-limb measurements in FeI lines show changes in both the line profiles and the limb darkening curves that appear to be characteristic of many other solar lines. Here we seek the constraints placed on the atmospheric model by these effects. We find that in addition to a depth varying source function we must also allow the ratio of the continuous absorption coefficient to the total absorption coefficient to pass through a minimum in the mid-photosphere. Such an effect is consistent with inward increases of the Doppler width and damping constant in the upper photosphere and an inward increase of the ionization for both iron and hydrogen in the low photosphere.The National Center for Atmospheric Research and Kitt Peak National Observatory are sponsored by the National Science Foundation.     

Equator-pole effect in the central intensities of some strong solar Fraunhofer lines

Uncorrected central intensities of the Fraunhofer lines NaD₁ and D₂, Mgb₁ and b₂, and Hβ have been determined at a number of points along the S-W limb of the sun, from equator to pole, using photographic spectra taken at the Locarno station of the Göttingen Observatory. No significant pole-equator variation could be found in excess of the observational errors which are of the order of 2%.     

Computation and observation of Zeeman multiplet polarization in Fraunhofer lines

In a first order approximation the influence of meridional circulations in a spherical shell on the radial dependence of the angular velocity is studied. Due to stationarity the flux of angular momentum which is transported through any sphere by the circulations must be cancelled by the flux of angular momentum due to turbulent friction. If the circulation goes equatorward at the outer surface the law of rotation must be such that angular momentum is transported in outward direction through the sphere.     

An empirical,statistical model for the formation of the cores of chromospheric Fraunhofer lines

Profiles of the Ba ii 4554 resonance line and the Mg i 4571 intercombination line are presented, observed near the limb of the Sun. They are obtained from eclipse spectrograms with good spectroscopic resolution and an accurate height calibration. The reduction of the observations is described and detailed profiles are given for a range of viewing angles (1/cos = 4 – 22).     

The BATSE search for absorption lines

No absorption lines between 15 and 100 keV have been detected in burst spectra accumulated by BATSE. Almost 250 bursts have been inspected visually, and a computerized search has begun. Our simulations show that BATSE could indeed detect lines similar to those observed byGinga in strong bursts, and our tests of the detectors' actual capabilities demonstrate they function as understood. The apparent discrepancy between BATSE andGinga is not yet compelling, and therefore the BATSE nondetections do not invalidate theGinga detections. Nonetheless, the absence of BATSE line detections indicates a low line-occurrence frequency.     

A search for a consistent model for the electromagnetic spectrum of the Crab nebula

An attempt is made to search for a consistent model to explain the electromagnetic spectrum of the Crab nebula (Tau A). It is assumed that there is a continuous injection of electrons at the centre of the nebula with an energy spectrumE ^–1.54 as evidenced by radio data. This spectrum must steepen to a slope larger than 2 at some energyE _i in order to ensure that the energy input into electrons remains finite. The spectrum must also steepen beyond an energyE _c depending on the magnetic field because of synchrotron energy losses. Two types of models are considered: Class I, in which the whole nebula is characterised by a uniform magnetic field, and Class II, in which besides the general fieldH ₀, small filamentary regions of strong fieldH _s are postulated.In models of Class I, the best fit to the observed data is obtained whenE _t >E _c andH ₀5×10^–4 gauss. However, this predicts a decrease in X-ray source size beyond 40 KeV. There are two possibilities of Class II model depending on the residence time of electrons in strong field regions being small or large. The former case explains the flattening in the optical spectrum.Experiments to distinguish between the various models are indicated.Presented at the International Conference on Cosmic Rays, Budapest, 1969.     

Magneto-sensitive lines in the solar spectrum

In this paper a numerical solution of the equations of transfer of the Stokes parameters in the presence of magnetic fields has been carried out. This yields the profiles of the Stokes parameters for three magneto-sensitive spectral lines (FEI λλ 6302.499, 6173.341, 5250.216). The magnetic broadening, temperature sensitivity and some other properties of these lines have also been investigated.In Unno's pioneering work, an algebraic solution of the equations of transfer of the Stokes parameters were obtained under a series of assumptions. Two of these are: 1) The source function B, varies linearly with the optical depth τ_λ; 2) The atmosphere follows the Milne-Eddington model. In this paper we have abandoned both these unrealistic assumptions. In consequence, our numerical solution agrees with observations better than the algebraic solution of Unno.