Molecular line haze opacity in sunspots

It has been shown that bound-bound opacity due to electronic transitions of molecules CN, CaH, MgH, and TiO explains, in a first approximation, the line haze opacity postulated by Zwaan (1974) for the region 0.5 m to 0.9 m of the umbral spectrum.     

Thermal infrared opacity of the Mars atmosphere

A refined technique is presented for deriving 9-μm extinction opacities of the Mars atmosphere from brightness temperature measurements made by the Viking Infrared Thermal Mapper. Improvements include modeling of the vertical temperature profile, a surface-atmosphere temperature discontinuity, and the effects of surface emissitivity and particle scattering. The routine is applied to the Mars Average Data Set to yield zonal mean opacities for more than one Mars year. The mean 9-μm opacity for one year is 0.5, yet the mode value is only 0.056, due to the very skewed distribution. Time histories of opacity at the Viking Lander 1 and 2 sites are generated and compared to in situ data. Opacity maps are presented for the period L_s 168–270 covering the 1977a dust storm; these show the genesis and spread of the storm with 10° L_s resolution.     

On molecules in sunspots

Spectra of umbrae of several sunspots in the wavelength region 4000–8000 Å scanned photoelectrically at the Göttingen Locarno Observatory were used in order to search for absorption lines of molecules. Several thousands of lines of known molecules were reidentifled (see Table II and Table III). Newly identified molecules are CoH, NiH and H₂O (see Table IV and Wöhl (1969a)). The Zeemann effect on molecular lines (of MgH and CaH; see Table V and Wöhl (1969b)) in spectra of umbrae was detected.     

On the umbra-penumbra area ratio of sunspots

The area ratio of umbra to penumbra (A_u/A_p) was investigated for a series of 126 sunspots observed around the maximum of solar activity in 1980. Plotting log (A_u) as function of log (A_p) a linear relation is obtained with a slope of 1.10, yielding an average ratio A_u/A_p of 0.24 for small spots and of 0.32 for large spots. This deviates noticeably from the commonly adopted constant value of A_u/A_p = 0.21 (Allen, 1973) used e.g. for modelling the sunspot irradiance deficit (cf. Willson et al., 1981) from the Solar Geophysical Data.Mitteilungen aus dem Kiepenheuer-Institut Nr. 328     

On AlF lines in sunspots

Intensity factors for bands of the C-A transition of the AlF molecule are calculated. A reinvestigation for the lines of (0, 0) band of the C-A system in sunspot spectra is suggested, so as to resolve the questionable existence of AlF absorption lines in sunspots.     

On the dynamics of the chromosphere above sunspots

The brightness oscillations of a sunspot umbra in the H and Ca⁺ K lines are studied. The observational results are explained in terms of the resonance theory of slow-mode magnetohydrodynamic waves in the sunspot chromosphere. The thickness of the chromosphere above a sunspot varies quasi-periodically from 420 km to 1000 km.     

On magneto-optical effects in sunspots

Magneto-optical effects on the circular polarization within the line FeI 6302.5 are investigated. Quantitative results on the V-reversal near the line centre are given for homogeneous magnetic fields.     

On the difference in darkness between sunspots

The effects of the magnetic field as well as the velocity field on sunspot equilibrium are discussed. The gas pressure difference, P, between a spot and the environments in the same horizontal layer is primarily determined by the magnetic field. Using recent model atmospheres we find that P shows a maximum value, P _max, at a depth of 650 ± 150 km below the photosphere. The value of P _max suggests that the curvature of the field lines is important for the equilibrium.It appears that, at an optical depth of unity in the umbra, the density has a value close to that of the environment at the same geometric depth (see Figure 4). If such is the case the expression for the umbra temperature (Equation (15)) may be considerably simplified (Equations (17) and (18)) and compared with observations.     

On the gamma system of nitric oxide in sunspots

With the aim of investigating the resonance system of NO, equivalent width calculations have been made for the 213.575 nm, Q ₁(31.5) line of the 1–0 band of -system of NO for the photospheric HSRA model, and for the line 214.012 nm, Q ₁(25.5) line of the same band system for Zwaan's (1974) sunspot model.Calculations show that -band system would not show up in the photospheric spectrum whereas a sunspot model yields an equivalent width of 72 mÅ suggesting that sunspots may provide relatively more favourable conditions for the detections of the resonance systems of some abundant molecules in the inaccessible ultraviolet region.     

On magnetic field gradients in sunspots

This paper is devoted mainly to a method of determining the gradient of magnetic fields. Utilizing the numerical solution of the equations of transfer of the Stokes parameters, we have calculated quantities characterizing the asymmetry and the amount of rotation of the wings of the “o” and “e” profiles of the magnetically sensitive line Fe Iλ 6302.499 as functions of the magnetic field gradient. The results of calculations have been verified with our own spectrophotometric observations of a large sunspot. The range of validity of the method is discussed, and the possible influence of the presence of magnetic field gradients on the observational data of magnetographs is investigated.     

On the width distribution of penumbral filaments in sunspots

The mean width and distribution of penumbral filaments of a sunspot have been estimated, using white light photographs obtained with a vacuum, Newtonian type, telescope. Three areas corresponding to the penumbra of a sunspot have been analysed. Data were collected during the solar eclipse of June 1973. The photometric profiles of the Moon limb over the photosphere have been analysed to obtain useful information on both, atmospheric and instrumental perturbation on each exposure. The mean value of the width of penumbral filaments is 0.37 arc sec.Now at INTA-Villafranca, S.T.S., P.O. Box 54065, Madrid, Spain.     

On the continuum intensity of the umbra of large sunspots

Spectral observations of large sunspots during the period June 1968 – Dec. 1969 in five wavelength regions between 4795 and 6775 are discussed. Selecting the best observations of two very large sunspots, we find slightly lower umbral intensities than derived by earlier observers. It is suggested that the small difference may be explained by the fact that earlier observers have used an average value, whereas we believe that the minimum value gives a more correct estimate of the umbral intensity.     

On the problem of active longitudes of sunspots and flares

The active longitudes of indices for sunspot activity and solar flares were detected and investigated by the method of isoline for the period July 1, 1957 to December 31, 1962. In the most active hemisphere of the sun the active longitudes of sunspot and flares appear to coincide. It is shown that the rate of concentration in the active longitudes is the highest for more important formations. Arguments for the reality of the active longitudes of sunspot areas are advanced. In conclusion the question of the influence of the uncertainty of the solar rotation period on the detection of active longitudes of flares is considered.     

On the O2 Schumann-Runge band system in sunspots

The visibility in the umbral ultraviolet spectrum of the O₂ Schumann-Runge absorption band system has been explored. It is found that the band system may be visible in high dispersion sunspot spectrum.     

On the topology of filaments and chromospheric fibrils near sunspots

The similarity between the spiral topology of chromospheric fibrils and filaments observed in H near sunspots and the configuration of an axisymmetric force-free magnetic field is examined. It is suggested that some of the observed features could be interpreted in terms of the configuration of lines of force of an axisymmetric force-free chromospheric magnetic field. Implications of the results of analysis to the possible interpretations of other observed topological features near a sunspot are discussed.Visiting scientist at the High Altitude Observatory.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Sponsored by the Office of Naval Research, Contract No. N 00014-67-C-0290.