Measurements of Electron Anisotropy in Solar Flares Using Albedo with RHESSI X-Ray Data

The angular distribution of electrons accelerated in solar flares is a key parameter in the understanding of the acceleration and propagation mechanisms that occur there. However, the anisotropy of energetic electrons is still a poorly known quantity, with observational studies producing evidence for an isotropic distribution and theoretical models mainly considering the strongly beamed case. We use the effect of photospheric albedo to infer the pitch-angle distribution of X-ray emitting electrons using Hard X-ray data from RHESSI. A bi-directional approximation is applied and a regularised inversion is performed for eight large flare events to deduce the electron spectra in both downward (towards the photosphere) and upward (away from the photosphere) directions. The electron spectra and the electron anisotropy ratios are calculated for a broad energy range, from about ten up to ～?300 keV, near the peak of the flares. The variation of electron anisotropy over short periods of time lasting 4, 8 and 16 seconds near the impulsive peak has been examined. The results show little evidence for strong anisotropy and the mean electron flux spectra are consistent with the isotropic electron distribution. The 3σ level uncertainties, although energy and event dependent, are found to suggest that anisotropic distribution with anisotropy larger than ～?three are not consistent with the hard X-ray data. At energies above 150?–?200 keV, the uncertainties are larger and thus the possible electron anisotropies could be larger.     

Equilibrium erosion of soft rock shores with a shallow or absent beach under increased sea level rise

A process-based numerical model was used to explore the response of soft rock shores with low volume beaches to variable rates of sea level rise. Equilibrium recession rates were simulated for ranges of wave height and period, tidal amplitude, rock strength, beach volume and rate of sea level rise. Equilibrium shore profiles were found to be steeper with higher rates of sea level rise. Beaches were represented as protective surfaces yet were found to cause no significant reduction in equilibrium recession rate when their volumes were below a critical threshold. Reduced equilibrium recession rates were found with beaches that extended sufficiently far below low tide level. The model results imply that, given several constraints, a very simple relationship exists between increased rates of sea level rise and the response of eroding composite soft rock/low volume beach shores.     

The estimation of acid dissociation constants in sea-water media from potentiometric titrations with strong base. II. The dissociation of phosphoric acid

The three dissociation constants of phosphoric acid have been determined in seawater media over the temperature and ionic strength ranges 5–30°C and 0.3-0.9 m. The results obtained fitted the equations (concentrations in mol per kg of solution):

$\text{pK}{}_{\mathrm{1P}}\text{=}\text{-75}\text{T}\text{+2.16-0.35I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rmsdeviation 0.034}\text{)}$

$\text{pK}{}_{\mathrm{2P}}\text{=}\text{737.6}\text{T}\text{++4.176-0.851I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rmsdeviation 0.015}\text{)}$

$\text{pK}{}_{\mathrm{3P}}\text{=}\text{2404}\text{T}\text{+1.31-0.87I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rmsdeviation 0.17}\text{)}$

The results are only in moderate agreement with those of Kester and Pytkowicz (1967). The reason for this lies partly in differences between the pH scales adopted and partly in the poor precision inherent in their method.     

The effects of storms and storm-generated currents on sand beaches in Southern Maine, USA

Storms are one of the most important controls on the cycle of erosion and accretion on beaches. Current meters placed in shoreface locations of Saco Bay and Wells Embayment, ME, recorded bottom currents during the winter months of 2000 and 2001, while teams of volunteers profiled the topography of nearby beaches. Coupling offshore meteorological and beach profile data made it possible to determine the response of nine beaches in southern Maine to various oceanographic and meteorological conditions. The beaches selected for profiling ranged from pristine to completely developed and permitted further examination of the role of seawalls on the response of beaches to storms.

Current meters documented three unique types of storms: frontal passages, southwest storms, and northeast storms. In general, the current meter results indicate that frontal passages and southwest storms were responsible for bringing sediment towards the shore, while northeast storms resulted in a net movement of sediment away from the beach. During the 1999–2000 winter, there were a greater percentage of frontal passages and southwest storms, while during the 2000–2001 winter, there were more northeast storms. The sediment that was transported landward during the 1999–2000 winter was reworked into the berm along moderately and highly developed beaches during the next summer.

A northeast storm on March 5–6, 2001, resulted in currents in excess of 1 m s⁻¹ and wave heights that reached six meters. The storm persisted over 10 high tides and caused coastal flooding and property damage. Topographic profiles made before and after the storm demonstrate that developed beaches experienced a loss of sediment volume during the storm, while sediment was redistributed along the profile on moderately developed and undeveloped beaches. Two months after the storm, the profiles along the developed beaches had not reached their pre-storm elevation. In comparison, the moderately developed and undeveloped beaches reached and exceeded their pre-storm elevation and began to show berm buildup characteristic of the summer months.     

Supraglacial and proglacial valleys on Amazonian Mars

Abundant evidence exists for glaciation being an important geomorphic process in the mid-latitude regions of both hemispheres of Mars, as well as in specific environments at near-equatorial latitudes, such as along the western flanks of the major Tharsis volcanoes. Detailed analyses of glacial landforms (lobate-debris aprons, lineated valley fill, concentric crater fill, viscous flow features) have suggested that this glaciation was predominantly cold-based. This is consistent with the view that the Amazonian has been continuously cold and dry, similar to conditions today. We present new data based on a survey of images from the Context Camera (CTX) on the Mars Reconnaissance Orbiter that some of these glaciers experienced limited surface melting, leading to the formation of small glaciofluvial valleys. Some of these valleys show evidence for proglacial erosion (eroding the region immediately in front of or adjacent to a glacier), while others are supraglacial (eroding a glacier’s surface). These valleys formed during the Amazonian, consistent with the inferred timing of glacial features based on both crater counts and stratigraphic constraints. The small scale of the features interpreted to be of glaciofluvial origin hindered earlier recognition, although their scale is similar to glaciofluvial counterparts on Earth. These valleys appear qualitatively different from valley networks formed in the Noachian, which can be much longer and often formed integrated networks and large lakes. The valleys we describe here are also morphologically distinct from gullies, which are very recent fluvial landforms formed during the last several million years and on much steeper slopes (∼20-30° for gullies versus ?10° for the valleys we describe). These small valleys represent a distinct class of fluvial features on the surface of Mars (glaciofluvial); their presence shows that the hydrology of Amazonian Mars is more diverse than previously thought.     

Uranium-series disequilibrium in Australian soils and its effect on aerial gamma-ray surveys

Measurements of U and ²²⁶Ra in 445 soil samples collected from areas throughout Australia show that these soils have a mean U content of 2.0 mg kg⁻¹ and activity ratio (U/²²⁶Ra) of 1.09. There is a wide spread in individual values but, overall, more soils are U-rich than ²²⁶Ra-rich. Some indications of regional disequilibrium were found, with ²²⁶Ra-rich soils being noted in the Southern Cross-Kambalda area (WA), in south-eastern Eyre Peninsula (SA) and in an area north of Cobar (NSW). Uranium-rich soils were found in two Carboniferous volcanic terrains in north-eastern Queensland. The spread in activity ratio values indicates that disequilibrium will contribute to the noise in U channel data obtained by aerial gamma-ray surveying. The combination of statistical noise from low count rates (reflecting the low U concentrations in soils) and U-²²⁶Ra disequilibrium combine to give variances of 40–60% in typical U channel data. Data appearance can be improved to some extent by appropriate filtering.     

The prediction of major Baltic inflows

Summary A recent informal attempt at Baltic inflow prediction is described. This forecast was based on the theory that the occurrence of major Baltic inflows is to a large extent determined by advection under the large-scale Atlantic windfield, rather than by purely local meteorological events over the Baltic itself. The forecast, completed in January 1972, proved to be successful, with the inflow beginning in April. Further tests of this simple technique of inflow prediction are planned.

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Vorausberechnung größerer Zuflüsse zur Ostsee

Zusammenfassung Es wird ein kürzlich vorgenommener informeller Versuch beschrieben, größere Zuflüsse zur Ostsee vorauszusagen. Diese Voraussage basierte auf der Theorie, daß die Zuflüsse weitgehend bestimmt werden durch Advektion unter dem großräumigen atlantischen Windfeld, und nicht so sehr durch rein lokale meteorologische Ereignisse über der Ostsee selbst. Die im Januar 1972 fertiggestellte Voraussage erwies sich als richtig, denn im April begann ein erneuter Zufluß. Weitere Tests dieser einfachen Technik der Zufluß-Voraussage sind geplant.

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La prédiction des principaux apports en Baltique

Résumé On décrit un essai de prévision des apports en Baltique fait récemment, d'une façon officieuse. Cette prédiction était basée sur la théorie suivant laquelle la venue des principaux apports en Baltique est, en grande partie, déterminée par l'advection à une grande échelle du champ des vents de l'Atlantique, plutôt que par la situation météorologique purement locale au-dessus de la Baltique elle-même. La prévision faite en janvier 1972 s'est révélée exacte pour l'apport commençant en avril. On projette de nouveaux essais de cette technique simple de prévision de l'apport.

     

Solubilities of metallic sulfides and quartz in hydrothermal sulfide solutions

Thermal waters contain small amounts of dissolved sulfides which in places precipitate at or near the earth’s surface. Knowledge of the physical chemistry of hydrothermal solutions is needed at elevated temperatures and pressures. Therefore, solubilities of the epithermal minerals cinnabar, stibnite, quartz, and orpiment in aqueousNa ₂ S solutions was determined from 25–250° C, 1–2000 bars, and at severalNa ₂ S concentrations. All the minerals are appreciably soluble inNa ₂ S solutions. Pressure increase decreases solubilities of metallic sulfides but slightly increases quartz solubility. Temperature increase causes increased solubility at temperatures above 150° C, but at lower temperatures, cinnabar, orpiment and quartz show solubility decreases with increasing temperatures. Quartz and cinnabar are mutually soluble, but in the presence of stibnite only a small amount of cinnabar dissolves. The second ionization constant ofH ₂ S as calculated from the solubility data ranges from 10^?16,21 at 0°C to 10^?12,59 at 250°C. TheK ₂ ofH ₂ S is lower according to this study than any reported before, and the variation with temperature is several orders of magnitude greater than had been predicted.     

Evaluation of radioactive anomalies using radium isotopes in ground waters

An empirical scheme based on the concentrations of uranium and the three alpha-emitting radium isotopes ²²⁶Ra, ²²⁴Ra and ²²³Ra is proposed for rating the significance of ground waters with respect to uranium exploration. The scheme has been developed from the results for over 200 water samples from the vicinity of known uranium deposits and radium anomalies in areas of Australia with climates varying from arid to tropical. The scheme uses relative levels of the four factors to rate the potential of a sample as good, possible or poor. An example of the use of the system in ground-water exploration in the Frome Embayment, South Australia, is presented to illustrate the value of the scheme in rejecting falsely anomalous samples with high uranium concentrations whilst detecting nearby uranium mineralization from drill holes not intersecting mineralization.     

The influence of rock resistance on coastal morphology around Lord Howe Island,southwest Pacific

An Erratum has been published for this article in Earth Surface Processes and Landforms 27(7) 2004, 931. Lord Howe Island, in the northern Tasman Sea, is a remnant of a much larger Late Miocene basaltic shield volcano. Much of the island's coastline is exposed to waves that have unlimited fetch, but a marked contrast is provided by a fringing coral reef and lagoon that very effectively attenuate wave energy along a portion of the western coastline. The geology of the island is varied, with hard and resistant basalt lavas, breccias and tuffs of intermediate resistance, and highly erodible eolianites. This variability provides an excellent opportunity to examine the in?uence of rock resistance on the development of the spectacular rock coast landforms that occur around the island. The hardness of rocks and the extent of weathering around the coastline were assessed using a Schmidt hammer, and statistical analysis was undertaken to remove outlying values. On all but one occasion, higher mean rebound values were returned from fresh surfaces than weathered surfaces, but only half of these differences were statistically signi?cant. Shore platforms with two distinct levels are juxtaposed along two stretches of coastline and Schmidt hammer results lend support to hypotheses that the raised surfaces may be inherited features. Relative rock resistance was assessed through a combination of Schmidt hammer data and measurements of joint density, and constrained on the basis of morphological data. This approach formed a basis for examining threshold conditions for sea‐cliff erosion at Lord Howe Island in the context of the distribution of resistant plunging cliffs and erosional shore platforms. Copyright © 2004 John Wiley & Sons, Ltd.