A Century of Solar Ca <Emphasis Type="SmallCaps">ii</Emphasis> Measurements and Their Implication for Solar UV Driving of Climate

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 Kodaikanal, Mt. Wilson, and US National Solar Observatories. Certain differences between the individual plage indices appear to be caused mainly by differences in the spectral passbands used. Our main finding is that the indices show remarkably consistent behavior on the multidecadal time scales of greatest interest to global warming studies. The reconstruction of solar ultraviolet flux variation from these indices differs significantly from the 20th-century global temperature record. This difference is consistent with other findings that, although solar UV irradiance variation may affect climate through influence on precipitation and storm tracks, its significance in global temperature remains elusive.     

Quasi-viscous accretion flow – I. Equilibrium conditions and asymptotic behaviour

In a novel approach to studying viscous accretion flows, viscosity has been introduced as a perturbative effect, involving a first-order correction in the α-viscosity parameter. This method reduces the problem of solving a second-order non-linear differential equation (Navier–Stokes equation) to that of an effective first-order equation. Viscosity breaks down the invariance of the equilibrium conditions for stationary inflow and outflow solutions, and distinguishes accretion from wind. Under a dynamical systems classification, the only feasible critical points of this 'quasi-viscous' flow are saddle points and spirals. On large spatial scales of the disc, where a linearized and radially propagating time-dependent perturbation is known to cause a secular instability, the velocity evolution equation of the quasi-viscous flow has been transformed to bear a formal closeness with Schrödinger's equation with a repulsive potential. Compatible with the transport of angular momentum to the outer regions of the disc, a viscosity-limited length-scale has been defined for the full spatial extent over which the accretion process would be viable.     

The future of large format HgCdTe arrays for astronomy

Rockwell has developed the 256×256 NICMOS3 FPA for the Hubble Space Telescope under funding from NASA through the University of Arizona. Since 1989, dozens of science grade devices have been delivered to astronomers throughout the world for ground based infrared observations. These devices have excellent sensitivity at 77K with mean dark currents of 0.1 e-/s, noise of 25 e-, and quantum efficiency of 55–70%. Pixel yields as high as 99.9% have been achieved. Our present plans are to develop a 1024×1024 FPA with 2.5 micron cutoff and make it available to astronomers. Such large arrays are made possible by the advances in detector material size (3 in. diameter PACE-I wafers), multiplexer advances (ability to verify the design in detail and availability of advanced foundries), and novel hybridization and reliability approaches.     

Lewis Cliff 87223, an anomalous enstatite chondrite and the diversity of enstatite chondrites

We studied a thin section of Lewis Cliff (LEW) 87223, an unusual EL3-related, enstatite chondrite (EC) that has primary and secondary features not observed in other ECs. We studied its metal-rich nodules, possible shock features, and chondrules, eight of which are Al-rich chondrules (ARCs). LEW 87223 has petrologic and compositional features similar to EL3s. Enstatite is the dominant mineral; chondrule boundaries are well defined; Si content of metal (0.5–0.6 wt%) is consistent with typical EL3; it has Cr-bearing troilite, oldhamite, and alabandite; and its O-isotopic composition is similar to other ECs. However, metal abundance in LEW 87223 (~13 vol%) is slightly higher than in other EL3s and its metal nodules are texturally and mineralogically different from other ECs. Both high and low Ni metals are present, and its alabandite has higher Fe (27.8 wt% Fe) than in other EL3s. Silicates appear darkened in plane polarized light, largely due to reduction of Fe from silicate. A remarkable feature of LEW 87223 is the high abundance of ARCs, which contain Ca-rich plagioclase and varying amounts of Na-rich plagioclase along chondrule edges and as veins. This suggests Na metasomatism and the possibility of hydrothermal fluids, potentially related to an impact event. LEW 87223 expands the range of known EC material. It shows that ECs are more diverse and record a wider range of parent body processes than previously known. LEW 87223 is an anomalous EL3, potentially the first member of a new EC group should similar samples be discovered.     

Application of drone-captured thermal imagery in aiding in the recovery of meteorites within a snow-covered strewn field

The rapid recovery of meteorites mitigates the exposure of astromaterials to the terrestrial environment and subsequent contamination. Modern fireball observatories have enabled the more accurate triangulation of fireball trajectories, which has aided in the location of strewn fields, in the case of meteorite-producing events. Despite this advancement, most meteorite searches still use manual searching to locate any meteorite falls, which is often labor-intensive and has a slow coverage rate (km² day⁻¹). Recent work has begun exploring the application of drone technology to the recovery of meteorites; however, most of this work has focused on falls in arid environments. Our study examines the utilization of drones with thermal imaging technology to aid in the recovery of meteorites that have fallen on a snow-covered field. We created a simulated strewn field that included meteorite specimens as well as Earth rocks with similar properties (“meteowrongs”). Thermal imagery was utilized to determine whether the thermal contrast between meteorites and snow could aid in the identification of meteorites. We found that the thermal contrast was significant enough that meteorites were readily identifiable within thermal images; however, it was not significant enough to distinguish between the meteorites and the meteowrongs. The utilization of thermal imagery in conjunction with visible imagery has the potential to aid in the rapid recovery of meteorites in snow-covered landscapes.     

The Japanese National Large Telescope (JNLT) project

The astronomical community in Japan is promoting a national project to construct a large optical infrared telescope on Mauna Kea in Hawaii. The scientific objectives and the basic concept of the project are briefly presented, as they stand in September 1984.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

The Death of Compact Binary Stars

Merging rates for compact binaries (double neutron stars or black holes) are calculated based on modern concepts of binary star evolution. It is found that the first laser interferometers, with rms sensitivities of 10-21 at a frequency of 100 Hz, can detect 10-700 black holes and only 1 neutron star coalescences in a 1-year integration time. The implications of evolutionary effects for the cosmological origin of gamma ray bursts are also discussed.     

K emission-line widths and the solar chromosphere

Closely spaced microphotometer tracings parallel to the dispersion of one excellent frame of a K-line time sequence have been utilized for a study of the nature of the K_2v , K_2R intensities in the case of the solar chromosphere. The frequency of occurrence of the categories of intensity ratio are as follows: per cent; per cent; per cent; per cent; per cent. Two types of absorbing components are postulated to explain the pattern of observed K_2v , k_2R intensity ratios. One component with minor Doppler displacements acting on the normal K₂₃₂ profile, where K_2V >K_2R , produces the cases K_2v K_2R , K_2v = K_2R , K_2v <K_2R . The other component arises from dark condensations which are of size 3500 kms as seen in K_2R . They have principally large down flowing velocities in the range 5–8 km/sec and are seen on K₃ spectroheliograms with sizes of about 5000 kms, within the coarse network of emission. These dark condensations give rise to the situation K_2R = 0.K₂-line widths are measured for all tracings where K_2v , K_2R are measurable simultaneously. The distribution curve of these widths is extremely sharp. The K₂ emission source is identified with the bright fine mottles visible on the surface. Evidence for this interpretation comes from the study of auto-correlation functions of K₂ intensity variations and the spacing between the bright fine mottles from both spectrograms and spectroheliograms. The life time of the fine mottling is 200 sec.The supergranular boundaries which constitute the coarse network come in two intensity classes. A low intensity network has the fine mottles as its principal contributor to the K emission. When the network is bright, the enhancement is caused by increased K emission due to the accumulation of magnetic fields at the supergranule boundary. The K₂ widths of the low intensity supergranular boundary agree with the value found for the bright mottles. Those for the brighter network are lower than this value, similar to the K₂ widths as seen in the active regions.It is concluded that bright fine mottling is responsible for the relation, found by Wilson and Bappu, between K emission line widths and absolute magnitudes of the stars.The paper discusses the solar cycle equivalents that stellar chromospheres can demonstrate and indicates a possible line of approach for successful detection of cyclic activity in stellar chromospheres.