William C. Livingston

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[1] Variations in the total solar irradiance (TSI) associated with solar activity have been argued to influence the Earth's climate system, in particular when solar activity deviates from the average for a substantial period. One such example is the 17th Century Maunder Minimum during which sunspot numbers were extremely low, as Earth experienced the Little(More)
High-resolution infrared spectra of sunspot umbrae have been recorded with the 1-meter Fourier transform spectrometer on Kitt Peak. The spectra contain a very large number of water absorption features originating on the sun. These lines have been assigned to the pure rotation and the vibration-rotation transitions of hot water by comparison with(More)
Infrared spectral observations of sunspots from 1998 to 2011 have shown that on average sunspots changed, the magnetic fields weakened, and the temperatures rose. The data also show that sunspots or dark pores can only form at the solar surface if the magnetic field strength exceeds about 1500 G. Sunspots appear at the solar surface with a variety of field(More)
We report the detection of the line of Si ix using the McMath-Pierce telescope on Kitt Peak. 2 23 2s 2 p P 1 r 0 Observations were made of the solar disk and at various heights above the limb between 2002 May 13 and 17, under nonideal sky conditions, using the 13.5 m vertical spectrograph and an InSb single-diode detector. We report a new rest wavelength(More)
The rst time simultaneous measurements of sodium column density and the absolute ux from a sodium laser guide star, created by a monochromatic 3 W cw laser, tuned to the peak of the sodium D 2 hyperrne structure, were conducted at the MMT and CFA 60 inch telescope in 1997. The results show that linearly and circularly polarized laser returns are(More)
Solar carbon monoxide spectra indicate the existence of a cool (less than 4000 kelvin) component to the solar chromosphere coexisting with the hot, bright gas at 6000 to 7000 kelvin. However, both the existence and the location of the cool component have been controversial. New high-resolution spectra show that carbon monoxide goes into emission just beyond(More)
Caliciopsis canker is an emerging problem in Pinus growing regions of Eastern North America. The fungal disease caused by Caliciopsis pinea is associated with overstocked stands and poor sites, but few quantitative data are available. The objective of this study, therefore, was to assess the extent and severity of Caliciopsis canker and to explore(More)
Spectroheliograms and disk-integrated flux monitoring in the strong resonance line of Ca II (K line) provide the longest record of chromospheric magnetic plages. We compare recent reductions of the Ca II K spectroheliograms obtained since 1907 at the Ko-daikanal, Mt. Wilson, and US National Solar Observatories. Certain differences between the individual(More)
Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant measurements from 1980 to 1986 are compared with ground-based, irradiance spectrophotometry of selected Fraunhofer lines. Both data sets were identically sampled and smoothed with an 85-day running mean, and the ACRIM total solar irradiance (S) values were corrected for sunspot blocking(More)