Radon gas, useful for medical purposes, safely fixed in quartz

Radon gas is enclosed in quartz or glass ampules by subjecting the gas sealed at a low pressure in the ampules to an ionization process. This process is useful for preparing fixed radon sources for radiological treatment of malignancies, without the danger of releasing radioactive gases

The coarse structure of the solar atmosphere

Observations of the quiet sun at wavelengths from 3 Å to 75 cm show (with two exceptions: the Ovi line at 1032 Å and possibly the continuum at 1.2 mm) either no limb brightening or less than had been supposed. On the other hand, the brightness temperature is observed to increase with wavelength in the millimeter and centimeter range. If this increase is due to greater visibility of hot overlying material, that material ought to be evident at the limb at shorter wavelengths, resulting in limb brightening. The only possible explanation for the absence of limb brightening at almost all wavelengths is that the emitting surface is rough at all wavelengths, with a scale of roughness approximately equal to the scale height at each temperature. Contradictions with existing models, along with the additional observations required for an improved model are discussed

Rotation in prominences

We have studied rotation in non-eruptive limb prominences; in most cases dopplergrams could be used to confirm proper motion measurements. In some cases part of the prominence rotates; in the others, the entire body is in rotation. Velocities of 15–75 km s⁻¹ are found. Of fifty-one prominences studied in 1978, five showed rotation

The coarse structure of the solar atmosphere

Observations of the quiet sun at wavelengths from 3 Å to 75 cm show (with two exceptions: the Ovi line at 1032 Å and possibly the continuum at 1.2 mm) either no limb brightening or less than had been supposed. On the other hand, the brightness temperature is observed to increase with wavelength in the millimeter and centimeter range. If this increase is due to greater visibility of hot overlying material, that material ought to be evident at the limb at shorter wavelengths, resulting in limb brightening. The only possible explanation for the absence of limb brightening at almost all wavelengths is that the emitting surface is rough at all wavelengths, with a scale of roughness approximately equal to the scale height at each temperature. Contradictions with existing models, along with the additional observations required for an improved model are discussed

The Caltech solar site survey, 1965-1967

We describe the Caltech solar site survey in 1965–1967 directed by R. B. Leighton. The solar seeing at 102 locations in 34 sites in Southern California was evaluated by 6009 visual estimates with portable telescopes. Cloud cover and other meteorological factors were also measured, and sunlight recorders were operated at several sites. We have reanalyzed much of the data to determine its consistency and learn what else we could about the sites. The visual estimates show good internal consistency and correlation with photographic data. The seeing was found to be best at various sites associated with water, and we point out the importance of the Bowen ratio in determining the influence of water vapor on seeing. It was found that seeing at the different sites was not well correlated in time. The seeing was found to be best at Lake Elsinore, an inland sink. Good seeing was also found on the Caltech campus and at Big Bear Lake in the San Bernardino Mountains. Taking into account the better sky transparency and the feasibility of constructing an observatory in the lake, we chose Big Bear Lake for the site of a new observatory. The lack of correlation of seeing with transparency suggests the benefits of several smaller telescopes, targeted at specific goals, located at sites chosen for those goals

Persistent 1.5 s oscillations superimposed to a solar burst observed at two mm-wavelengths

Long-enduring quasi-periodic oscilations (1.5s) superimposed upon a solar burst have for the first time been observed simultaneously at two different mm-wavelengths (22 GHz and 44 GHz). The oscillations were present throughout the burst duration (about 10 min), and were delayed at 44 GHz with respect to 22 GHz by 0.3 s. The relative amplitude of the oscillation was of about 20% at 44 GHz and of about 5% at 22 GHz. Interferometer measurements at 10.6 GHz indicated the burst source position stable within 1 arc sec. An He I D₃ line flare showed two persistent small spots separated by about 10 arc sec. The 22/44 GHz burst position corresponds well with the location of the He I D₃ spots. The oscillations display features which distinguish them from ultrafast time structures found in other bursts. One possible interpretation is a modulation of the synchrotron emission of trapped electrons by a variable magnetic field on a double burst source, optically thin at 44 GHz and with optical thickness ⪞ 0.3 at 22 GHz

850 μm Observations of the 11 July 1991 Total Solar Eclipse

We present observations of the 11 July 1991 total solar eclipse made from the Caltech Submillimeter Observatory. The 850 μm limb is extended 3380±140 km above the visible limb, and there is a 10% brightening at the extreme limb. The measured limb height agrees with previous work at shorter and longer wavelengths. The run of limb heights with wavelength is well fit by a single electron density scale height. We argue that there is no need to invoke spicule geometry to explain the observations