A complete photoelectric sunspot spectrum: An atlas from 3900–8000 Å

Complete photoelectric spectra of the photosphere as well as of both umbra and penumbra of a typical sunspot, ranging from 3900–8000 Å, have been obtained at the Locarno observatory. An automatic scanning device, a high precision electronic divider and an on-line Oscillomink penless recorder enabled us to eliminate the noise produced by image distortion and to scan the entire visible spectrum within just 5 h. The recordings have a linear dispersion of about 50 mm/Å and a spectral resolution of 40 mÅ or better. Simultaneously with these observations the momentary continuous spot intensity and its fast variation with time due to seeing variations have been recorded with a frequency resolution up to 100 Hz. In order to provide as much data as possible for the correction of the umbral spectrum for parasitic light, we also measured the limb profile and the aureola intensity at several wavelengths.At present, the recordings are being processed and combined into an atlas, which we plan to make available in either numerical or graphical form.As a first result, we compare our corrected continuous sunspot intensities with those of other authors and derive standard reference data on the radiation of both umbra and penumbra of a typical sunspot. Finally we make a comparison between some radiative properties of sunspots and late-type stellar atmospheres.     

Zur Bildung von Zinn-Wolfram-Lagerstätten

Ohne Zusammenfassung     

Aurorae during the Maunder Minimum

Summary Based on a comprehensive review of scientific sources from the 17th and 18th century, a new table of auroras for the years 1645–1705 is presented. Comparison of these data with long-time German recordings (latitude 50 to 55 N) demonstrates that the assumption of the Maunder Minimum is not confirmed by the data of the auroras.With 4 Figures     

Polarimetry of solar pores

We address the magnetic field structure of solar pores. The data were obtained at the Gregory Coudè telescope at Izaña using the AT1 CCD camera system to observe pores with three spectral lines: one magnetically sensitive line, recording all 4 Stokes profiles, and two g = 0 lines where only the intensity profiles were measured. The data reduction included the standard procedure (removing dark current and flatfielding) as well as destretching of the polarimetric spectra and removing the non-magnetic straylight by means of a 2-d deconvolution of the observed intensity variation using a Lucy-Richardson restoration algorithm. In the following analysis we first determined the temperature- and pressure stratification of the pore using the g = 0 lines and then applied an inversion of the Stokes profiles to get the parameters of the magnetic field. Across the pore we find a strong variation of the resulting field strength as well as of the inclination and the azimuth, consistent with the assumption of a canopy forming in the higher atmosphere.     

The influence of capacitor effects on the surface potential of satellites with partially insulating surfaces in the solar wind

A simple model is presented for the estimation of the surface potential of satellites with insulating coating. Any small area F of the surface is represented by a capacitor, which is charged up by the plasma and photoelectron currents. Using simple approximations for the currents, the surface potential is calculated for plasma parameters supposed to describe the solar wind between 0.3 a.u. and 1 a.u. distance from the Sun.The potential of the shaded side of the satellite is found to depend strongly on the capacitance of the surface. High capacitances or high spin frequency for the spacecraft can be used to limit the potential differences on the surface. In any case the angular surface potential distribution is asymmetric with respect to the solar wind velocity.     

Improving fluorometry as a source tracking method to detect human fecal contamination

In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, targeted sampling was combined with fluorometry. Targeted sampling works by identifying hot spots of fecal contamination through multiple samplings over ever-decreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. Because organic matter fluoresces and interferes with fluorometry, two locations were chosen for sampling: waters relatively low in organic matter at Mayagüez Bay, Puerto Rico, and waters relatively high in organic matter at St. Simons Island, Georgia. In Puerto Rico, targeted sampling and fluorometry quickly and easily identified two hot spots of human fecal contamination in the Yagüez River, which flows through the city of Mayagüez. Another source tracking method, detection of theesp gene, confirmed their human origin. On St. Simous Island, targeted sampling and fiuorometry identified two hot spots of potential human fecal contamination. Detection of theesp gene confirmed the human origin of one site but not the other, most likely because background organic matter fluorescence interfered with fhiorometry. A separate experiment showed that adding a 436-um emission filter to the fluorometer reduced this background fluorescence by > 50%. With the 436-nm Filter in place, another sampling was conducted on St. Simons Island, and the second hot spot was identified as fecal contamination from birds. As long as the fluorometer was equipped with a 436-nm filter and organic matter concentrations were considered, targeted sampling combined with fluorometry was a relatively inexpensive method for identifying human fecal contamination in water.