NLTE Model of a Quiescent Filament

The Sacramento Peak Observatory VTT Echelle Spectrograph was used to obtain high resolution spectrograms of the filament at W06° S27° observed on April 9, 1991 in hydrogen Hα, Hβ, and CaII H and λ 8498 lines. The line profiles were measured and digitized. A numerical code based on the MALI approach with partial frequency redistribution (PRD) in resonance lines was applied to obtain theoretical profiles of hydrogen and CaII lines. As a result of fitting the observed and calculated profiles, the physical parameters of the filament plasma were obtained. They include temperature, gas pressure, electron density and turbulent velocity.

Performance of a stabilized Fabry-Perot solar analyzer

A unique solar lineshift analyzer described by Rust, Burton and Leistner (1986) has been used at the Sacramento Peak Observatory to study solar oscillations. Operation of this “Stablized Solar Analyzer” (SSA) depends on the electro-optic effect in crystalline lithium niobate, the substrate of the solid Fabry-Perot etalon. Voltage on the etalon shifts the passband by ∼ 4.5 × 10−4 Å/V. The etalon has a passband of 0.175 Å at 6102.7 Å. The stabilization system uses a tunable diode laser to relate the Fabry-Perot passband to the D2 line of atomic Cs 133, at 8521.46 Å. This system reduced instrumental noise to less than Δλ/λ = 10−9 over a six-hour interval.

The Measurement of Long-Period Oscillations at Sacramento Peak Observatory and South Pole

A program to measure long-period brightness oscillations at the solar limb has been pursued at Sacramento Peak Observatory for several years. Past improvements in observing technique and data analysis are reviewed. The encouraging results aid in the verification of the reality and the origin of oscillatory signals. However, the main stumbling block to this and other observational programs is the length of observing sequences imposed by the day/night cycle. The South Pole has received considerable attention as a site where extended observations might be possible. Currently, the Sacramento Peak program is developing a South Pole telescope designed for the observing technique and data analysis proven in Sunspot. A review of pertinent South Pole site parameters is given here for other workers who may be considering South Pole observations. Observing sequences longer than 150 hr are possible, though rare. Data sets of this duration are very attractive for solar oscillation studies.

The Evolution of an Average Solar Granule

High-resolution photographic spectra of the center of the solar disk have been obtained with the Vacuum Tower Telescope at Sacramento Peak Observatory. Two weak iron lines and the neighboring continuum were recorded with 40 sec time resolutions and better than 1” spatial resolution over a period of 40 min. Intensity and velocity fluctuations were obtained in the two lines and continuum as a function of time and space, and 300 sec oscillations were filtered out. The resulting fluctuations, due solely to granulation, were assembled into an ensemble average of the center of a granule and the center of an intergranular lane, as a function of time. The intensity-fluctuation data have been analyzed through calculation of model line profiles to yield temperature fluctuations in a granule as functions of time and height. We find that the line parameters are distinctly out of phase with continuum brightness, so that, for example, maximum brightness at line center occurs approximately 100 sec prior to maximum continuum brightness. A series of one-dimensional model atmospheres representing the granule at various stages of its lifetime is presented.