William Livingston

Ca ii K2V spectral features and their relation to small-scale photospheric magnetic fields

Although the Ca ii K232 network is known to be cospatial with magnetic elements there has been doubt as to the magnetic origin of the fainter K2V points. We demonstrate that weak magnetic elements also lie at the roots of the K2V points, and because the latter are numerous they may contribute sensibly to the integrated light profile of Ca ii K.

Observations of sunspot umbral velocity oscillations.

Sunspot umbral molecular lines have been used to look for the oscillatory velocities in the umbra. Power spectrum analysis showed conspicuous power for periods in the range between 448 and 310 s. The maximum peak-to-peak amplitude of the umbral oscillatory velocity component is observed to be in the order of 0.5 km s−1.

Solar rotation, 1966–1978

Photospheric and chromospheric spectroscopic Doppler rotation rates for the full solar disk are analyzed for the period July, 1966 to July, 1978. An approximately linear secular increase of the equatorial rate of 3.7% for these 12 years is found (in confirmation of Howard, 1976). The high latitude rates above 65 ° appear to vary with a peak-to-peak amplitude of 8%, or more, phased to the sunspot cycle such that the most rapid rotation occurs at, or following, solar maximum. The chromosphere, as indicated by Hα, has continued to rotate on the average 3% faster than the photosphere agreeing with past observations. Sources of error are discussed and evaluated.

Spectral analysis and the two-dimensional distribution of physical parameters in a quiescent prominence

The profiles of Hα and Ca ii K lines of a arch quiescent prominence on April 1, 1971 have been analyzed and the two-dimensional distributions of electron temperature Te, micro-turbulence velocity vt and the column number density of hydrogen along the line-of-sight NH have been obtained. Te, υt, and NH are found to be 7500 K, 6 km s−1 and 2.2 × 1018 cm−2 on an average, respectively. The electron temperature at the central part of the prominence and along the two arcades are greater than that at the edges, while the distribution of the micro-turbulence velocity in these regions is opposite. There is no systematic variation in Te and vt, from the center to the periphery as described by Hirayama (1971). The column number density in the central region is lower than that at the two edges.The contour lines of Te, υt, and NH are predominantly vertical rather than horizontal. This implies that the height-variation of physical parameters in filamentary structure is small. The arrangement of this structure in the prominence is likely to be arched and is probably in the direction of magnetic field lines.

SOLAR ROTATION: THE PHOTOSPHERIC HEIGHT GRADIENT.

For selected pairs of Fraunhofer lines the height of formation has been calculated corresponding to that portion of the profile intercepted by the magnetograph exit slits. A photospheric height discrimination of 150–300 km is realized. In 1971 simultaneous measurements of equatorial angular velocity from spectroscopic displacements of these line pairs indicate no height gradient in excess of 1%.The disturbing influence of telluric line blends is analyzed. It is proposed that undetected telluric lines could account, at least in part, for the photospheric height gradient which has been found in a number of photographic investigations.

Detection of small scale structure in metal lines at the extreme solar limb

We describe a tangential limb spectrum at 5870 Å which geometrically probes the high photosphere through the low chromosphere. Velocity and brightness structures with sizes ranging from 500 to 1500 km are present in the stronger emission lines. Such structure is consistent between the Fe i and Ba ii lines, and emission knots in these lines coincide with continuum bright streaks. But no correlation is evident between structure in the He i D3 line, emission in the Na i D2 line, and emission in the Fe i and Ba ii lines as a group. Two classes of near-horizontal velocity structure are seen in the height range from 0 to 500 km above the limb: υ ⪝ 1 km s−1 for the weaker metals and υ ∼ 7–10 km s−1 for the Na i line. Differences in line opacity are suggested as the cause of the low correlation between the fine structure in the various lines.

Evidence for downflow following a coronal transient

On 11 September 1973 a peculiar prominence was observed. The prominence displayed strong (∼ 50km s−1) systematic motions toward and away from the observer. The unusual spectrographic appearance of the prominence might have been due to downflowing material lifted into the corona during an earlier coronal transient.