New 1982 — 1990 photometry of λ Andromedae and its 11-year cycle

We present photoelectric photometry of λ And never before published, obtained between February 1982 and December 1990 at 29 different observatories. Then we combine it with all other photometry available to us (previously published, contained in the I.A.U. Commission 27 Archives, and obtained with the Vanderbilt 16-inch automatic telescope but not yet published), to yield a 14.8-year data base. Analysis reveals a long-term cycle in mean brightness, with a full range of 0^m.15 and a period of 11.4 ± 0.4 years. Because most of our new photometry was concentrated in the 1983-84 observing season, we analyze that one well-defined light curve with a two-spot model. Spot A keeps a 0^m.04 amplitude throughout four rotation cycles whereas the amplitude of spot B diminishes from 0^m.09 down almost to 0^m.03. The spot rotation periods were 55^d.9 ± 0^d.6 and 520^d.8 ± 1^d.0, respectively.     

Earliest mountain forests

It's hard to imagine the Rockies or the Alps without forests, but until about 360 million years ago the Earth's mountains were probably bare of vegetation. Almost a Martian landscape, this was a world of rocky screes, mudflows and flash floods. Lichen may have clung here and there, but as for large plants, most were restricted to wetland delta-plains close to sea level. But everything was about to change. The evolution of the seed in Late Devonian times altered the face of our planet forever. Analogous to the reptile egg in the animal kingdom, the seed freed plants from the necessity of surface water for reproduction, and paved the way for the invasion of mountainous terrain.     

The Jet Driven Motions in the Narrow Line Region of NGC 1068

We have obtained HST FOC f/48 long-slit spectroscopy of the central 2 arcseconds of the Narrow Line Region of NGC 1068 between 3500-5400\OA with a spectral resolution of 1.78\OA/pixel. At a spatial scale of 0″.0287 per pixel these data provide an order of magnitude improvement in resolution over previous ground based spectra and allow us to trace the interaction between the radio jet and the gas in the NLR. Our results show that, within ±0″.5 of the radio-jet the emission lines are split into two components whose velocity separation is 1500 km s-1. The emission line structure is reminiscent of that seen previously around the jet of 3C120. Furthermore, this material enveloping the radio-jet is in a much higher ionization state than that of the surrounding NLR gas. The highest excitation is coincident with the jet axis where emission in the coronal line of [FeVII] λ3769\OA is detected but where [OII] λ3727 \OA is depressed. These results imply that we are witnessing a cocoon of hot gas in expansion around the radio-jet created by its interaction with the gas, and that these shocks are sufficiently fast, at least ± km s-1, that they are creating localized ionization effects. This revised version was published online in July 2006 with corrections to the Cover Date.     

Properties of metre-wavelength solar bursts associated with coronal mass ejections

An investigation is made to determine the relationship between a coronal mass ejection (CME) and the characteristics of associated metre-wave activity. It is found that (1) the CME width and leading edge velocity can be highly influential in determining the intensity, spectral complexity and frequency coverage of both type II and continuum bursts; (2) the presence of a CME is possibly a necessary condition for the production of a metric continuum event and (3) metric continuum bursts as well as intense, complex type II events are preferentially associated with strong, long lasting soft X-ray events.     

Nature,origin and evolution of a Late Pleistocene incised valley‐fill,Sunda Shelf,Southeast Asia

Understanding the stratigraphic fill and reconstructing the palaeo‐hydrology of incised valleys can help to constrain those factors that controlled their origin, evolution and regional significance. This condition is addressed through the analysis of a large (up to 18 km wide by 80 m deep) and exceptionally well‐imaged Late Pleistocene incised valley from the Sunda Shelf (South China Sea) based on shallow three‐dimensional seismic data from a large (11 500 km²), ‘merge’ survey, supplemented with site survey data (boreholes and seismic). This approach has enabled the characterization of the planform geometry, cross‐sectional area and internal stratigraphic architecture, which together allow reconstruction of the palaeo‐hydrology. The valley‐fill displays five notable stratigraphic features: (i) it is considerably larger than other seismically resolvable channel forms and can be traced for at least 180 km along its length; (ii) it is located in the axial part of the Malay Basin; (iii) the youngest part of the valley‐fill is dominated by a large (600 m wide and 23 m deep), high‐sinuosity channel, with well‐developed lateral accretion surfaces; (iv) the immediately adjacent interfluves contain much smaller, dendritic channel systems, which resemble tributaries that drained into the larger incised valley system; and (v) a ca 16 m thick, shell‐bearing, Holocene clay caps the valley‐fill. The dimension, basin location and palaeo‐hydrology of this incised valley leads to the conclusion that it represents the trunk river, which flowed along the length of the Malay Basin; it connected the Gulf of Thailand in the north with the South China Sea in the south‐east. The length of the river system (>1200 km long) enables examination of the upstream to downstream controls on the evolution of the incised valley, including sea‐level, climate and tectonics. The valley size, orientation and palaeo‐hydrology suggest close interaction between the regional tectonic framework, low‐angle shelf physiography and a humid‐tropical climatic setting.     

Comparison between measured and modelled cloudless‐sky solar irradiances at the surface and at the top of the atmosphere

Abstract

Cloudless‐sky solar fluxes calculated by the radiative transfer algorithm used in the Canadian Climate Centre's general circulation climate model are compared with measurements of upwelling radiation at the top of the atmosphere (TOA) and downwelling radiation at the surface. The 12‐layer model partitions the solar spectrum into two broad wavebands (0.25–0.68 and 0.68–4.00 μm). The comparison utilized TOA fluxes estimated from Nimbus‐ 7 measurements and measured downwelling fluxes at the surface for Kalgoorlie, West Australia, and downwelling fluxes at the surface for Woodbridge, Ontario. Model estimates and measurements agreed to within experimental error for most solar zenith angles. Estimates improved, especially at Woodbridge, when aerosol effects were included. The mean bias error was less than 4% for surface irradiance and less than 6% for upwelling TOA irradiance, which produces a TOA albedo error of about 0.01.     

Calibration of the Soho/Lasco C3 White Light Coronagraph

We present a detailed review of the calibration of the LASCO C3 coronagraph on the SOHO satellite. Most of the calibration has been in place since early in the mission and has been utilized to varying degrees as required by specific analysis efforts. However, using observational data from the nearly decade-long database of LASCO images, we have re-evaluated and improved many aspects of the calibration. This includes the photometric calibration, vignetting function, geometric distortion, stray light, and exposure and observation times. Using this comprehensive set of corrections we have generated and made available a set of calibrated coronal images along with a set of periodic background images to ease the accessibility and use of the LASCO database. Deceased