Improved absorption cross-sections of oxygen in the wavelength region 205–240 nm of the Herzberg continuum

The laboratory values of the Herzberg continuum absorption cross-section of oxygen at room temperature from Cheung et al. (1986, Planet. Space Sci. 34, 1007), Jenouvrier et al. (1986a, Planet. Space Sci. 34, 253) and Jenouvrier et al. (1986, J. quant. Spectrosc. radiat. Transfer 36, 349) have been compared and re-analyzed. There is no discrepancy between the absolute values of these two sets of independent measurements. These values have been combined together in a linear least-squares fit to obtain improved values of the Herzberg continuum cross-section of oxygen at room temperature throughout the wavelength region 205–240 nm. Agreement with in situ and other laboratory measurements is discussed.     

Silicon X-ray line emission from solar flares and active regions

New observations of solar flare and active region X-ray spectra obtained with the Columbia University instrument on OSO-8 are presented and discussed. The high sensitivity of the graphite crystal panel has allowed both line and continuum spectra to be observed with moderate spectral resolution. Observations with higher spectral resolution have been made with a panel of pentaerythritol crystals. Twenty-nine lines between 1.5 and 7.0 Å have been resolved and identified, including several dielectronic recombination satellite lines to Si xiv and Si xiii lines which have been observed for the first time. It has been found that thermal continuum models specified by single values of temperature and emission measure have fitted the data adequately, there being good agreement with the values of these parameters derived from line intensity ratios.     

High resolution absorption cross-section measurements of N2O at 295–299 K in the wavelength region 170–222 nm

High resolution absorption cross-section measurements of N₂O at 295–299 K have been performed in the wavelength region 170–222 nm with a 6.65 m scanning spectrometer/spectrograph of sufficient resolution to yield cross-sections that are independent of the instrumental function. The measured cross-sections are presented graphically and are available throughout the region 44925–58955 cm^?1 at intervals of 0.1–0.2 cm^?1 as a numerical tabulation stored on magnetic tape from the National Space Science Data Center, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Previously unresolved details of the banded structure which is superposed on the continuous absorption in the region 174–190 nm are observed.     

A phase and amplitude study of auroral pulsations

To supplement a rocket investigation of the auroral green line, data from some auroral pulsations have been analyzed by direct integration of the time-dependent continuity equations for each of the sources now thought to contribute. It is shown that indirect processes are not incompatible with studies of auroral pulsations, and that a non-negligible contribution to the green-line intensity comes from dissociative recombination. Calculations using the theoretical O(¹S) lifetime show that the remaining green line must come from a direct or very fast process; however, if the O(¹S) lifetime can be reduced, significant portions of the green line can come from the transfer of energy from N₂(A³Σ_u⁺) to atomic oxygen.     

High resolution absorption cross section measurements and band oscillator strengths of the (1, 0)−(12, 0) Schumann-Runge bands of O2

Cross sections of O₂ at 300 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 179.3–201.5 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines mm^?1 grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross sections of the Schumann-Runge bands (12, 0) through (1, 0) in this wavelength region are absolute, i.e., independent of the instrumental width, a result not achieved previously. The measured cross sections are presented graphically and are available at wavenumber intervals of > sim; 0.1 cm^?1 as numerical complications stored on magnetic tape from the National Space Science Data Center, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Band oscillator strengths of the (12, 0) through (1, 0) bands have been determined by direct numerical integration of the measured cross sections.     

Coronal electron density maps for 7 March, 1970, derived from Mgx λ625 spectroheliograms

We have analyzed daily Mgx 625 spectroheliograms acquired by the Harvard College Observatory experiment on OSO-6 for a 28-day period centered on 7 March, 1970, the date of a well-observed total solar eclipse. These data are used to construct maps of the variation across the solar disk of the electron density at the base of the corona. The correspondence of high and low density regions with regions of enhanced and reduced emission in white light and Mgx pictures made during or near the time of the eclipse are described.     

Coastal dune conservation on an Irish commonage: community-based management or tragedy of the commons?

In Ireland 'commonage' refers to lands jointly owned by several individuals who have grazing rights. Commonage can provide the low-intensity grazing regime regarded as optimal for habitat conservation, and it is also unlikely to suffer the negative impacts of building development or coastal engineering. Today, however, the traditional control systems of coastal commonage are generally moribund, leading to habitat degradation. The only viable future management model is likely to be one based on local community control. Community management would have the legitimacy to counter the negative perceptions of external authority that generate environmental degradation.