Convection flow over a uniform-flux vertical surface with variable viscosity

A regular perturbation analysis is presented for natural convection flow over an uniform flux vertical surface with temperature dependent viscosity. Numerical calculations are presented forP _r=6.7 which show that the first-order correction to the local temperature difference and to the local skin-fraction are negative whereas it is positive for the local Nusselt number. The effects of variable viscosity on the temperature, velocity profiles, the local temperature difference, the local Nusselt number and the local skin fraction are discussed.     

Subsurface structural trends of the offshore Nile Delta area, Egypt: evidences from gravity and magnetic data

Subsurface structural trends and tectonics affecting the offshore Nile Delta area, Egypt, have been studied through the interpretations of gravity and magnetic data. Reduced to the pole, regional–residual separation, Tilt derivative and Euler deconvolution techniques are applied for the processing and interpretations of the magnetic and gravity data. The average depth of the sedimentary cover, estimated from the two-dimensional power spectrum technique ranges between 8 km and 13 km. The interpretation of the gravity and magnetic data indicates that the study area is affected by many subsurface structural trends. The NW–SE is the major trend related to El-Temsah and Misfaq-Bardwil trend. The NE–SW direction is the second dominant trend, related to the Rosetta trend. Other trends defined through the interpretation of gravity and magnetic data include: the N–S direction, related to the Baltim fault trend, the E–W direction, related to the Neogene hinge line and the NNE–SSW related to the Gulf of Aqaba. Accessory trends include the ENE–WSW, WNW–ESE and finally the NNW–SSW.     

Inorganic geochemical evidence for the depositional facies associations of the Upper Jurassic Chia Gara Formation in NE Iraq

Four wells (K-109, Hr-1, Tk-3, and Bj-1) in NE Iraq (including parts of the Kurdistan Region) were selected to study the Tithonian–Berriasian Chia Gara Formation from the inorganic geochemical point of view. The intervals studied in each well occurred at present-day burial depths of Hr-1 3,075–3,310 m; K-109 2,780–3,090; Tk-1 2,770–2,890; and Bj-1 2,150–2,310 m. A total of 16 samples from the four studied wells were investigated geochemically using X-ray fluorescence in order to measure their major element oxides and their trace element contents. Among the major oxides, CaO has the highest weight percentages in all samples as expected in this limestone-dominated formation. SiO₂ and Al₂O₃ show higher concentrations only in well Bj-1 than the other sections, due to its shallower depth of deposition and its marginal location within the depositional basin. The general trace element distribution along all studied well successions showed good similarity. However, the ratios of V/Ni and V/Cr were of higher values in the lower part of the formation, which is considered as a good indicator to the deposition of this part of the formation within anoxic depositional environment. An exception was in well Bj-1, where the V/Ni ratio was lower in the this lower part of the formation than the upper part that may be due to the different lithology in this succession which is lacking distinct shale or calcareous shale beds. However, the V/Cr ratio can still indicate the prevailing of reducing condition because V/Cr ratios in all samples are >2. Also, Th/U ratio in the lower part of the studied successions was lower than the upper part, which is also coinciding with the domination of the reducing geochemical conditions in the depositional environment. It may be concluded from this study that the R-mode cluster analysis of the main oxides indicated to the main mineral constituent of the rock which is calcite. It is also confirmed that the SiO₂ and Al₂O₃ contents in the Chia Gara limestones are especially high in well Bj-1, particularly in the lower and upper parts of the succession. On the other hand, R-mode cluster analysis of the trace elements showed lower amounts of Zr and V in relation to silica and confirmed the random distribution of Sr and Ba in the studied samples. Q-mode cluster analysis indicated that the upper part of the studied formation is pure limestone in well H-1 and such purity of limestone beds also occurs in the lower part of the studied formation in well Tk-3. The elemental distribution within the sections as inferred from the studied samples indicates that the anoxic depositional conditions were prevailed during the Chia Gara Formation, especially during the accumulation of the lower part.     

The Use of Gamma Ray Spectrometry as an Aid for Uranium Exploration in Kab Amiri Area,Central Eastern Desert,Egypt

High‐resolution gamma ray spectrometry was exploited to locate the potential radioactive targets at Kab Amiri granite pluton, Central Eastern Desert, Egypt. The Kab Amiri pluton forms a concentric granitic body of monzogranite to syenogranite composition intruded into mafic‐ultramific rocks. To identify and detect anomalous concentrations of natural radioactive elements in the study area, contour maps of equivalent uranium (eU ppm), equivalent thorium (eTh ppm), potassium (K%) and their geochemical ratios (eU/Th, eTh/K and eU‐eTh/3.5) as well as standard deviation map of uranium were constructed and interpreted. Qualitative and quantitative interpretations of the spectrometric survey data revealed the presence of seven radioactive anomalies in the south of the studied area. These anomalies could be related to the prevailing faulting directions NE and ENE fault trends. The southernmost anomalous zone is related to high episyenitization and uranium concentrations. It exhibits a sharp increase in the eU concentrations reaching 370 ppm resulting in a high eU/eTh ratio reaching 4.5 and characterized by oval shape trending in the NE direction. Constructing the contour map of the (eU‐eTh/3.5) was helpful in defining the trends of uranium migration and enabling the delineation of the limit between the negative contours (leaching) and positive contours (deposition).     

Seismic and well logging interpretation for evaluation of the lower Bahariya reservoir,southwest Qarun (SWQ) Field,Gindi Basin,Egypt

This paper focuses on seismic and well log interpretations for evaluating the sandstones of the Cenomanian Bahariya Formation in the southwest Qarun Field, Gindi Basin, northern Western Desert of Egypt. The seismic profiles display a clear anticlinal structure intersected by reverse faults in the study area. This faulted anticline has been interpreted to be one of the Syrian arc system folds formed by Upper Cretaceous tectonic inversion, which resulted from the NW movement of the African Plate relative to Laurasia. This anticline has been recommended as a target for exploration by the present work as it may represent a structural trap for hydrocarbon accumulation. The sandstones of the Lower Bahariya Formation in the southwest Qarun Field display good reservoir characteristics. The interpretation of the available well log data for the SWQ-21 and SWQ-25 wells for the Lower Bahariya Formation reflects a good reservoir quality for oil production in its topmost part. This reservoir possesses low S_W (<50%), high porosity (16%), low S_W/S_XO and low BVW (<0.09) which all reflect a high potential for oil production.     

Consistency of precipitation products over the Arabian Peninsula and interactions with soil moisture and water storage

The regional-scale consistency between four precipitation products from the GPCC, TRMM, WM, and CMORPH datasets over the Arabian Peninsula was assessed. Their macroscale relationships were inter-compared with soil moisture and total water storage (TWS) estimates from AMSR-E and GRACE. The consistency analysis was studied with multivariate statistical hypothesis testing and Pearson correlation metrics for the period from January 2000 to December 2010. The products and GRACE estimates were assessed over a representative sub-domain (United Arab Emirates) with available in situ well observations. Next, geographically temporally weighted regression (GTWR) was employed to examine the interdependencies among the peninsula’s hydrological components. The results showed GPCC-TRMM recording the highest correlation (0.85) with insignificant mean differences over more than 90% of the peninsula. The highest GTWR predictive performance of TWS (R² = 0.84) was achieved with TRMM forcing, which indicates its potential to monitor changes in TWS over the arid peninsular region.     

Update earthquake risk assessment in Cairo,Egypt

The Cairo earthquake (12 October 1992; m _b  = 5.8) is still and after 25 years one of the most painful events and is dug into the Egyptians memory. This is not due to the strength of the earthquake but due to the accompanied losses and damages (561 dead; 10,000 injured and 3000 families lost their homes). Nowadays, the most frequent and important question that should rise is “what if this earthquake is repeated today.” In this study, we simulate the same size earthquake (12 October 1992) ground motion shaking and the consequent social-economic impacts in terms of losses and damages. Seismic hazard, earthquake catalogs, soil types, demographics, and building inventories were integrated into HAZUS-MH to produce a sound earthquake risk assessment for Cairo including economic and social losses. Generally, the earthquake risk assessment clearly indicates that “the losses and damages may be increased twice or three times” in Cairo compared to the 1992 earthquake. The earthquake risk profile reveals that five districts (Al-Sahel, El Basateen, Dar El-Salam, Gharb, and Madinat Nasr sharq) lie in high seismic risks, and three districts (Manshiyat Naser, El-Waily, and Wassat (center)) are in low seismic risk level. Moreover, the building damage estimations reflect that Gharb is the highest vulnerable district. The analysis shows that the Cairo urban area faces high risk. Deteriorating buildings and infrastructure make the city particularly vulnerable to earthquake risks. For instance, more than 90 % of the estimated buildings damages are concentrated within the most densely populated (El Basateen, Dar El-Salam, Gharb, and Madinat Nasr Gharb) districts. Moreover, about 75 % of casualties are in the same districts. Actually, an earthquake risk assessment for Cairo represents a crucial application of the HAZUS earthquake loss estimation model for risk management. Finally, for mitigation, risk reduction, and to improve the seismic performance of structures and assure life safety and collapse prevention in future earthquakes, a five-step road map has been purposed.     

New variations of Mg II emission lines of Mira AB with HST

This paper presents results from high resolution observations of the Mira AB binary system taken by the HST (Hubble Space Telescope) in the ultraviolet region through the period (1999–2004). By comparing the results using HST data with those obtained from the IUE (International Ultraviolet Explorer) observations through the period (1979–1995). we found new variations in the profiles, widths and fluxes of Mg II (k&h) emission lines. In addition to this it appears that there are another emission components at some phases in the red and blue sides of both Mg II (k&h) emission lines. These emission components may be of Mira A origin. There is a considerable shift of both Mg II (k&h) emission lines in observation taken on 2nd February 2004. The Mg II profiles extends up to more than 600 km/s, and redshifted as with IUE observations.     

A Major Geoeffective CME from NOAA 12371: Initiation,CME–CME Interactions,and Interplanetary Consequences

In this article, we present a multi-wavelength and multi-instrument investigation of a halo coronal mass ejection (CME) from active region NOAA 12371 on 21 June 2015 that led to a major geomagnetic storm of minimum \(\mathrm{Dst} = -204\) nT. The observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory in the hot EUV channel of 94 Å confirm the CME to be associated with a coronal sigmoid that displayed an intense emission (\(T \sim6\) MK) from its core before the onset of the eruption. Multi-wavelength observations of the source active region suggest tether-cutting reconnection to be the primary triggering mechanism of the flux rope eruption. Interestingly, the flux rope eruption exhibited a two-phase evolution during which the “standard” large-scale flare reconnection process originated two composite M-class flares. The eruption of the flux rope is followed by the coronagraphic observation of a fast, halo CME with linear projected speed of 1366 km?s^?1. The dynamic radio spectrum in the decameter-hectometer frequency range reveals multiple continuum-like enhancements in type II radio emission which imply the interaction of the CME with other preceding slow speed CMEs in the corona within \(\approx10\)?–?\(90~\mbox{R} _{\odot}\). The scenario of CME–CME interaction in the corona and interplanetary medium is further confirmed by the height–time plots of the CMEs occurring during 19?–?21 June. In situ measurements of solar wind magnetic field and plasma parameters at 1 AU exhibit two distinct magnetic clouds, separated by a magnetic hole. Synthesis of near-Sun observations, interplanetary radio emissions, and in situ measurements at 1 AU reveal complex processes of CME–CME interactions right from the source active region to the corona and interplanetary medium that have played a crucial role towards the large enhancement of the geoeffectiveness of the halo CME on 21 June 2015.