Effect of a self-induced electric field on the electron beam kinetics and resulting hard X-ray and microwave emissions in flares

The kinetics of beam electron precipitation from the top of a loop into the solar atmosphere with density gradients and an increasing magnetic field have been generally described. The Fokker-Planck equations are solved with regard to Coulomb collisions and the effect of the electric field induced by this beam. The photon spectra and polarization degree in hard X-ray (10–300 keV) and microwave (1–80 GHz) emissions are simulated under different assumptions regarding the beam electron distribution function. The simulation results are compared with the flare observations on March 10, 2001, and July 23, 2002, visible at different position angles. It has been indicated that the coincidence of the theoretical photon spectra with simultaneous observations of the hard X-ray and microwave emissions of these flares is the best for models that not only take into account collisions, but also the electric field induced by electron fluxes propagating in flare loops with very weakly or moderately converging magnetic fields.     

Upper Jurassic Rock Depositional Settings in the Baidar Valley and Evolution of the Crimean Carbonate Platform

The paper presents results of the lithological study of Upper Jurassic limestones, flyschoids and limestone breccias on the southern side of the Baidar Valley in the Crimean Mountains. Study of the microfacies revealed that the limestones are represented by deposits on lagoons, platform edge shoals, reefs, and forereef aprons on the carbonate platform slope. Flyschoids include deposits in the distributive turbidite channels and hemipelagic sediments in the deep-water part of the basin. Limestone breccias were formed by gravitation flows on the carbonate platform toe-of-slope and slope. The presence of gravitation deposits in the Upper Jurassic carbonate complexes of the Crimean Mountains can testify to the primary clinoform structure of this sedimentary sequence. Comparison of the obtained sedimentological data made it possible to reconstruct the facies model of the Crimean carbonate platform and main episodes of its formation. Development of the carbonate shelf was related to two transgressive-regressive cycles. A dome-shaped reef was formed away from the coast at the initial (Oxfordian) stage. The carbonate platform was formed at the early Kimmeridgian lowstand stage when sediments were deposited in the internal part of the platform adjacent to land. In the late Kimmeridgian and early Tithonian, configuration of the carbonate platform profile resembled a distally steepened ramp, and its active progradation and shelf expansion took place in the course of transgression. Regression in the late Tithonian–early Berriasian led to regressive transformation of the ramp into platform with a flattened shallow-water shelf. Tectonic deformations at the Jurassic/Cretaceous transition promoted the formation of megabreccias on the carbonate platform foreslope. The tectonically reworked rock sequence of the “extinct” carbonate platform was overlapped transgressively by the upper Berriasian or lower Valanginian, relatively deep-water deposits of the Cretaceous platform cover.     

Analysis and farmers’ perception of climate change in the Kashmir Valley,India

Theoretical and Applied Climatology - Analysis of climatic variables is important for the detection and attribution of climate change trends and has received considerable attention from researchers...     

Exploration rock geochemistry for gold, Parkes, New South Wales, Australia

The London-Victoria lode-type Au deposit near Parkes, New South Wales, was discovered in 1863 and became the subject of modern exploration in 1980 after about 75 years of little or no activity. The deposit lies within Palaeozoic tuffaceous, andesitic rocks. Soil geochemistry was the main technique used to define drill targets, and the deposit is now at an advanced state of assessment for probable development.Rock geochemistry is being investigated as an aid in drill-core interpretation in the search for extensions to the London-Victoria deposit and other similar deposits in the district.At an early stage of the rock-geochemical work it became clear that minor basemetal mineralization was also present in the structural hanging wall at between 30 and 70 m from the lode Au deposit. Interpretation of the geochemical signatures for major elements (Ca, Mg, Na, K, Fe) and trace elements (Cu, Pb, Zn, Mn) is confused by an overlap and merging of responses from the Au and base-metal mineralization. The measurement of bromine-soluble Sb, As, Bi, and Te, together with the more conventional major and trace elements, permits discrimination between geochemical halos related to the Au and those resulting from minor base metal mineralization.The results demonstrate the use of rock geochemistry for Au exploration, its usefulness in drawing attention to geological features, and the utility of bromine-soluble trace elements commonly associated with gold mineralization.     

Zr-in-rutile thermometry in blueschists from Sifnos, Greece

Zr-in-rutile thermometry on samples of blueschist from Sifnos, Greece, yields temperatures that reflect progressive crystallization of rutile from ca. 445 to 505°C with an analytical precision of + 18/−27 and ± 10°C using the electron microprobe and ± 1.5–3.5°C using the ion microprobe. Individual grains are generally homogeneous within analytical uncertainty. Different grains within a single sample record temperature differences as large 55°, although in most samples the range of temperatures is on the order of 25°. In several samples, Zr-in-rutile temperatures from grains within garnet are lower than temperatures from matrix grains, reflecting growth of rutile with increasing temperature of metamorphism. Although the specific rutile-producing reactions have not been identified, it is inferred that rutile grows from either continuous reaction involving the breakdown of lower grade phases (possibly ilmenite), or from pseudomorph reactions involving the breakdown of relic igneous precursors at blueschist-facies conditions. No systematic variation in rutile temperatures was observed across the blueschist belt of northern Sifnos, consistent with the belt having behaved as a coherent block during subduction.     

Delivering the two degree global climate change target using a flexible ratchet framework

Global climate negotiations have been characterized by a divide between developed and developing nations – a split which has served as a persistent barrier to international agreement within the United Nations Framework Convention on Climate Change process. Notable progress in bridging this division was achieved at the 21st Conference of the Parties meeting in Paris through the introduction of Intended Nationally Determined Contributions (INDCs). However, the collective ambition of submitted INDCs falls short of a global 2°C target, requiring an effective ratchet mechanism to review and increase national commitments. Inequitable distribution of additional responsibilities risks re-opening historic divisions between parties. This article presents a flexible ratchet framework which shares mitigation commitments on the basis of per capita equity in line with emerging requirements for a 2°C target. The framework has been designed through convergence between developed and developing nations; developed nation targets are based on an agreed standardized percentage reduction wherever emissions are above per capita equity; developing nations are required to peak emissions at or below per capita equity levels by an agreed convergence date. The proposed framework has the flexibility to be integrated with current INDCs and to evolve in line with shifting estimates of climate sensitivity.

Policy relevance

The outcome of the 21st Conference of the Parties (COP21) negotiations in Paris offered mixed results in terms of level of ambition and submitted national commitments. A global agreement to keep average global temperature rise below two degrees was maintained; however, current pledged Intended Nationally Determined Contributions (INDCs) are projected to result in an average warming of close to three degrees. The implementation of a global ratchet mechanism to scale-up national commitments will remain key to closing this ambition gap to reach this two degree target. How this upscaling of responsibility is shared between parties will be a defining discussion point within future negotiations. This study presents a standardized, equity-based framework for how this ratchet mechanism can be implemented – a framework designed to be flexible for evolution in line with better understanding of climate sensitivity, and adaptable for integrations with current INDC proposals.     

Geology and geochemistry of archaean felsic metavolcanic rocks of the Eastern Part of the Kolar greenstone belt, Dharwar craton, India: Implications for their petrogenesis and geodynamic setting

In the Kolar greenstone belt of the Dharwar craton, felsic metavolcanics are encountered prominently in its eastern region around Surapalli and Marikoppa. These felsic volcanic rocks are essentially homogeneous and their bulk mineralogy is almost the same. They consist of phenocrysts of quartz and feldspar, set in a fine-grained quartzo-feldspathic groundmass. They are calc-alkaline rhyolite in composition, and are characterized by high SiO₂ (av. 75.74 wt.%), moderate Al₂O₃ (av. 11.84 wt.%), Na₂O (av. 3.55 wt.%), K2O (av. 3.26 wt%) contents and low Mg# (av. 6.07), Cr (av. 8 ppm), Ni (av. 8 ppm), Sr (av. 331 ppm.), Y (av. 7 ppm), Yb (av. 0.87 ppm) and Nb/Ta (av. 6.40) values, suggesting Tonalite-Trondhjemite-Granodiorite (TTG) affinity for these felsic volcanics. They are strongly fractionated [(La/Yb)_N? = 14.41–48.70] with strong LREE enrichment [(La/Sm)_N = 2.50-3.59] and strong HREE depletion [(Gd/Yb)_N = 1.34–2.77] with positive Eu anomaly. The regional geological set-up, petrographic and geochemical characteristics suggest that these felsic volcanics probably were derived by partial melting of a subducting basalt slab at shallow depth without much involvement of mantle wedge in an island arc geodynamic setting.     

ENCORE: the effect of nutrient enrichment on coral reefs. Synthesis of results and conclusions

Coral reef degradation resulting from nutrient enrichment of coastal waters is of increasing global concern. Although effects of nutrients on coral reef organisms have been demonstrated in the laboratory, there is little direct evidence of nutrient effects on coral reef biota in situ. The ENCORE experiment investigated responses of coral reef organisms and processes to controlled additions of dissolved inorganic nitrogen (N) and/or phosphorus (P) on an offshore reef (One Tree Island) at the southern end of the Great Barrier Reef, Australia. A multi-disciplinary team assessed a variety of factors focusing on nutrient dynamics and biotic responses. A controlled and replicated experiment was conducted over two years using twelve small patch reefs ponded at low tide by a coral rim. Treatments included three control reefs (no nutrient addition) and three + N reefs (NH4Cl added), three + P reefs (KH2PO4 added), and three + N + P reefs. Nutrients were added as pulses at each low tide (ca twice per day) by remotely operated units. There were two phases of nutrient additions. During the initial, low-loading phase of the experiment nutrient pulses (mean dose = 11.5 microM NH4+; 2.3 microM PO4(-3)) rapidly declined, reaching near-background levels (mean = 0.9 microM NH4+; 0.5 microM PO4(-3)) within 2-3 h. A variety of biotic processes, assessed over a year during this initial nutrient loading phase, were not significantly affected, with the exception of coral reproduction, which was affected in all nutrient treatments. In Acropora longicyathus and A. aspera, fewer successfully developed embryos were formed, and in A. longicyathus fertilization rates and lipid levels decreased. In the second, high-loading, phase of ENCORE an increased nutrient dosage (mean dose = 36.2 microM NH4+; 5.1 microM PO4(-3)) declining to means of 11.3 microM NH4+ and 2.4 microM PO4(-3) at the end of low tide) was used for a further year, and a variety of significant biotic responses occurred. Encrusting algae incorporated virtually none of the added nutrients. Organisms containing endosymbiotic zooxanthellae (corals and giant clams) assimilated dissolved nutrients rapidly and were responsive to added nutrients. Coral mortality, not detected during the initial low-loading phase, became evident with increased nutrient dosage, particularly in Pocillopora damicornis. Nitrogen additions stunted coral growth, and phosphorus additions had a variable effect. Coral calcification rate and linear extension increased in the presence of added phosphorus but skeletal density was reduced, making corals more susceptible to breakage. Settlement of all coral larvae was reduced in nitrogen treatments, yet settlement of larvae from brooded species was enhanced in phosphorus treatments. Recruitment of stomatopods, benthic crustaceans living in coral rubble, was reduced in nitrogen and nitrogen plus phosphorus treatments. Grazing rates and reproductive effort of various fish species were not affected by the nutrient treatments. Microbial nitrogen transformations in sediments were responsive to nutrient loading with nitrogen fixation significantly increased in phosphorus treatments and denitrification increased in all treatments to which nitrogen had been added. Rates of bioerosion and grazing showed no significant effects of added nutrients. ENCORE has shown that reef organisms and processes investigated in situ were impacted by elevated nutrients. Impacts were dependent on dose level, whether nitrogen and/or phosphorus were elevated and were often species-specific. The impacts were generally sub-lethal and subtle and the treated reefs at the end of the experiment were visually similar to control reefs. Rapid nutrient uptake indicates that nutrient concentrations alone are not adequate to assess nutrient condition of reefs. Sensitive and quantifiable biological indicators need to be developed for coral reef ecosystems. The potential bioindicators identified in ENCORE should be tested in future research on coral reef/nutrient interactions. Synergistic and cumulative effects of elevated nutrients and other environmental parameters, comparative studies of intact vs. disturbed reefs, offshore vs. inshore reefs, or the ability of a nutrient-stressed reef to respond to natural disturbances require elucidation. An expanded understanding of coral reef responses to anthropogenic impacts is necessary, particularly regarding the subtle, sub-lethal effects detected in the ENCORE studies.     

Analysis of formation pressure test results in the Mount Elbert methane hydrate reservoir through numerical simulation

Targeting the methane hydrate (MH) bearing units C and D at the Mount Elbert prospect on the Alaska North Slope, four MDT (Modular Dynamic Formation Tester) tests were conducted in February 2007. The C2 MDT test was selected for history matching simulation in the MH Simulator Code Comparison Study. Through history matching simulation, the physical and chemical properties of the unit C were adjusted, which suggested the most likely reservoir properties of this unit. Based on these properties thus tuned, the numerical models replicating “Mount Elbert C2 zone like reservoir”, “PBU L-Pad like reservoir” and “PBU L-Pad down dip like reservoir” were constructed. The long term production performances of wells in these reservoirs were then forecasted assuming the MH dissociation and production by the methods of depressurization, combination of depressurization and wellbore heating, and hot water huff and puff. The predicted cumulative gas production ranges from 2.16 × 10⁶ m³/well to 8.22 × 10⁸ m³/well depending mainly on the initial temperature of the reservoir and on the production method.This paper describes the details of modeling and history matching simulation. This paper also presents the results of the examinations on the effects of reservoir properties on MH dissociation and production performances under the application of the depressurization and thermal methods.     

Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa

Anabranching is characteristic of a number of rivers in diverse environmental settings worldwide, but has only infrequently been described from bedrock-influenced rivers. A prime example of a mixed bedrock-alluvial anabranching river is provided by a 150-km long reach of the Orange River above Augrabies Falls, Northern Cape Province, South Africa. Here, the perennial Orange flows through arid terrain consisting mainly of Precambrian granites and gneisses, and the river has preferentially eroded bedrock joints, fractures and foliations to form multiple channels which divide around numerous, large (up to 15 km long and 2 km wide), stable islands formed of alluvium and/or bedrock. Significant local variations in channel-bed gradient occur along the river, which strongly control anabranching style through an influence on local sediment budgets. In relatively long (>10 km), lower gradient reaches (<0.0013) within the anabranching reach, sediment supply exceeds local transport capacity, bedrock usually only crops out in channel beds, and channels divide around alluvial islands which are formed by accretion in the lee of bedrock outcrop or at the junction with ephemeral tributaries. Riparian vegetation probably plays a key role in the survival and growth of these islands by increasing flow roughness, inducing deposition, and stabilising the sediments. Less commonly, channels may form by eroding into once-continuous island or floodplain surfaces. In shorter (<10 km), higher gradient reaches (>0.0013) within the anabranching reach, local transport capacity exceeds sediment supply, bedrock crops out extensively, and channels flow over an irregular bedrock pavement or divide around rocky islands. Channel incision into bedrock probably occurs mainly by abrasion, with the general absence of boulder bedforms suggesting that hydraulic plucking is relatively unimportant in this setting. Mixed bedrock-alluvial anabranching also occurs in a number of other rivers worldwide, and appears to be a stable and often long-lived river pattern adjusted to a number of factors commonly acting in combination: (1) jointed/fractured granitoid rock outcrop; (2) erosion-resistant banks and islands; (3) locally variable channel-bed gradients; (4) variable flow regimes.