Dynamics and energetics of the thermal and nonthermal components in the solar flare of January 20, 2005, based on data from hard electromagnetic radiation detectors onboard the CORONAS-F satellite

Based on data from the SONG and SPR-N multichannel hard electromagnetic radiation detectors onboard the CORONAS-F space observatory and the X-ray monitors onboard GOES satellites, we have distinguished the thermal and nonthermal components in the X-ray spectrum of an extreme solar flare on January 20, 2005. In the impulsive flare phase determined from the time of the most efficient electron and proton acceleration, we have obtained parameters of the spectra for both components and their variations in the time interval 06:43–06:54 UT. The spectral index in the energy range 0.2–2 MeV for a single-power-law spectrum of accelerated electrons is shown to have been close to 3.4 for most of the time interval under consideration. We have determined the time dependence of the lower energy cutoff in the energy spectrum of nonthermal photons E _γ0(t) at which the spectral flux densities of the thermal and nonthermal components become equal. The power deposited by accelerated electrons into the flare volume has been estimated using the thick-target model under two assumptions about the boundary energy E ₀ of the electron spectrum: (i) E ₀ is determined by E _γ0(t) and (ii) E ₀ is determined by the characteristic heated plasma energy (≈5kT (t)). The reality of the first assumption is proven by the fact that plasma cooling sets in at a time when the radiative losses begin to prevail over the power deposited by electrons only in this case. Comparison of the total energy deposited by electrons with a boundary energy E _γ0(t) with the thermal energy of the emitting plasma in the time interval under consideration has shown that the total energy deposited by accelerated electrons at the beginning of the impulsive flare phase before 06:47 UT exceeds the thermal plasma energy by a factor of 1.5–2; subsequently, these energies become approximately equal and are ～(4–5) × 10³⁰ erg under the assumption that the filling factor is 0.5–0.6.     

On the ground level enhancement beginning

Based on our analysis of the data fromthe global network of neutronmonitors for several events, we have found the times of the first increases in count rate at individual stations that precede the main solar cosmic-ray enhancement. The onset time of proton acceleration at the Sun has been determined from the appearance of a broad gamma-ray line with its maximum near 70 MeV that is generated during the decay of neutral pions, which, in turn, are produced when protons with energies above 300 MeV interact with the solar atmosphere. The time of the first recording of energetic protons at the Earth is delayed relative to the time at which these protons appeared at the Sun by 60–300 s, i.e., by a value comparable to the difference between the direct photon and particle propagation times. At least two conclusions follow from the existence of such “precursors”. First, the protons begin to escape from the solar atmosphere into interplanetary space immediately after their acceleration. Second, some of the protons traverse a path shorter than the nominal length of interplanetary magnetic field lines.     

New gravity maps of the Eastern Alps and significance for the crustal structures

The deep seismic profile Transalp crosses, from north to south, Germany, Austria and Italy. The gravity measurements for each country were made by national agencies with different reference systems and data reduction methods. Within the frame of the Transalp-project a comprehensive database of the Eastern Alps was compiled covering an area of 3.5° by 4° in longitude and latitude (275 by 445 km), respectively. To increase the data coverage in the south Alpine area two gravity surveys were carried out, resulting in 469 areally distributed new stations, of which 215 have been measured with the intent to improve the geoid in the area of the planned Brenner Basistunnel (BBT). The resulting gravity database is the best in terms of resolution and data quality presently available for the Eastern Alps. Here the free air, Bouguer and isostatic gravity fields are critically discussed. The spatial density of existing gravity stations in the three countries is discussed. On the Italian side of the Alps the spatial density is rather sparse compared to the Austrian side. The Bouguer-gravity field varies between − 190 * 10^− 5 m/s² and + 25 * 10^− 5 m/s², with the minimum located along the Alpine high topographic chain, but with a small offset (a few tens of km) to the greatest topographic elevation, showing that the Airy-type local isostatic equilibrium does not fully apply here. The maximum of the Bouguer anomaly has an elongated shape of 100 by 50 km located between the towns of Verona and Vicenza and covers the Venetian Tertiary Volcanic Province (VTVP), a feature not directly related to the plate collision in the Eastern Alps. The gravity high is only partly explainable by high-density magmatic rocks and requires also a deeper source, like a shallowing of the Moho. The isostatic residual anomalies (Airy model) are in the range ± 50 * 10^− 5 m/s², with the greatest positive anomaly corresponding to the location of the VTVP, indicating here under-compensation of masses. At last a discussion of a 2D density model based on reflection seismic data and receiver functions is made.     

Deep saltwater in Chalk of North-West Europe: origin, interface characteristics and development over geological time

High-concentration saltwaters occur in many places in the regional Chalk aquifers of North-West Europe; to investigate deep occurrences, profiles of interstitial porewater chemistry have been studied from three 250–450m deep cores drilled in the eastern parts of Zealand, Denmark. At the studied location, saline water in the Chalk resides at depths from 40 to 80m and salinity increases with depth. Concentrations of chloride up to ca. 30,000ppm have been observed at depths of 400m. Measured vertical hydraulic heads in open boreholes suggest that advective groundwater flow is now restricted in deeper parts of the Chalk formation and diffusive transport is thus the predominant transport mechanism. Laboratory-measured porosity and effective diffusion coefficients were used as input to a numerical 1D diffusion model of the interface between freshwater in an upper, fractured aquifer and modified connate formation water below. The model satisfactorily simulated the observed chloride and δ¹⁸O profiles. The diffusive refreshening of the Chalk formation has been going on for about 0.9 million years. The connate water in the Chalk of parts of the sedimentary basin seems to have been modified by transport of saltwater from underlying Mesozoic and Paleozoic sediments during compaction, which presumably ceased around 4 million years ago.     

Isotopic composition of a large photosymbiotic foraminifer: Evidence for hypersaline environments across the Great Australian Bight during the late Pleistocene

Analysis of carbon and oxygen isotopic compositions of large benthic foraminifera tests (Marginopora vertebralis) that lived in the Great Australian Bight during the late Pleistocene, reveal that the tests are enriched by 1 to 3‰ in both ¹⁸O and ¹³C relative to modern specimens from the same region. The intolerance of M. vertebralis for cool waters negates lower ocean water temperature as an explanation for such high δ¹⁸O values. The oxygen isotopic compositions are thus interpreted to reflect tests secreted in hypersaline waters of up to 56 ppt salinity, concentrated from seawater by evaporation. M. vertebralis thrives today in waters of similar salinity at Shark Bay, Western Australia. The Pleistocene sedimentary assemblage supports an interpretation that environments broadly similar to those in outer modern-day Shark Bay were wide spread across the Great Australian Bight during portions of marine isotope stages 2, 3 and 4. The high δ¹³C values of the Pleistocene M. vertebralis are interpreted to reflect enhanced photosynthetic activity that depletes dissolved carbonate in ¹²C in such shallow, saline settings. These hypersaline environments formed during periods of lower sea-level when shallow-waters (< 20 m depth) extended from the shoreline over ~ 100 km across what is currently a relatively deep shelf. This study indicates that shelf bathymetry was a critical determinant of past environments of deposition across the Great Australian Bight.     

完整岩石在不同尺度上的屈服

对完整岩石力学机制的研究有助于更好地理解与屈服有关的应力-应变关系。屈服准则研究方法包括基于实验数据分析和基于微观力学的研究。屈服数学理论的研究目标是对应力和应变关系的理论描述和对弹塑性界限的识别。本文主要研究完整岩石在不同尺度上的屈服。从Weibull理论可知,岩石强度随尺度增大而减少,这已经通过单轴压缩强度（UCS）的Hoek-Brown方程得到证实。然而,围压能改变岩石强度及屈服。因此,本文利用直径为50mm和96mm的圆柱形砂岩样品在不同围压作用下的压缩实验来研究不同尺度下的岩石屈服,从实验中提取不同尺度下的屈服初始点并描述屈服面,最终给出简单数学形式的屈服准则。     

Hydrochemical Groundwater Evolution in the Bunter Sandstone Sequence of the Odenwald Mountain Range,Germany: A Laboratory and Field Study

Field and laboratory investigations were performed to identify the principal mechanisms of the hydrochemical groundwater evolution among low mineralised groundwater in the Triassic Bunter sandstone aquifer of the Odenwald low mountain range, central Germany. Hydrochemical composition comprises low pH, SO₄-rich shallow groundwaters issued by springs (Ca-Mg-SO₄-type) grading to SO₄-poor deep groundwaters with near-neutral pH (Ca-HCO₃-type). Batch experiments of the original rock were run to determine primary mineral alteration reactions and the origin of dissolved ions. Principal experimental reactions comprise the decomposition of anorthite, K-feldspar, biotite and jarosite as mineral components of the original sandstone rock and the formation of clay minerals of the smectite group (Ca-montmorillonite, beidellite), and iron hydroxides as secondary minerals. Mobilisation of fluid inclusion in quartz grains contributes to Na and Cl concentrations in the leachates. The evolution of deep groundwater circulation proceeds by mineral alteration reactions calculated by the inverse modelling of both primary and secondary minerals to produce low-T mineral phases. The dissolution of K-feldspar converts Ca-montmorillonite to illite (illitisation). The formation of Na-beidellite correlates with decreasing concentration of Na in solution. Mineral reactions further proceed to the formation of kaolinite as stable mineral phase. As indicated by modelled adsorption curves, the decrease of SO₄ concentrations during groundwater evolution relates to the adsorption of SO₄ on iron hydroxides. The leaching of calcite indicated for individual groundwaters relates to the distribution of loess in the appropriate catchment areas.     

Assessment of weathering damage on the Petroglyphs of Cheonjeon-ri, Ulsan, Republic of Korea

The Petroglyphs of Cheonjeon-ri in the area of Ulsan Metropolitan City in the southeastern part of the Republic of Korea represent outstanding cultural property of the country. The rock carvings—discovered about 40 years ago—provide valuable information on the life of the ancient people of different periods. In 1973, the petroglyphs were designated Korean National Treasure. Apparently, the petroglyphs have suffered damage from weathering such as loss of stone material, current detachment of stone material and deposits on the stone surface. The protection of this masterpiece of historic rock carving has become an important concern in the country. Geoscientific studies were carried out, targeted to stone analysis and to characterization and rating of weathering damage. The diagnostic studies combined laboratory analysis of representative unweathered and weathered stone material and in situ investigation by means of profile measurements at the carvings, mapping of weathering forms, ultrasonic measurements and rebound hardness measurements. Methodology and results of the material and damage diagnosis are presented. The results on type and extent of damage in combination with deduced risk prognosis reveal a considerable threat to the historical site of Cheonjeon-ri due to weathering and they indicate the need of intervention for monument preservation.     

Olivine‐rich exposures at Bellicia and Arruntia craters on (4) Vesta from Dawn FC

We present an analysis of olivine‐rich exposures at Bellicia and Arruntia craters using Dawn Framing Camera (FC) color data. Our results confirm the existence of olivine‐rich materials at these localities as described by Ammannito et al. ( 2013a ) using Visual Infrared Spectrometer (VIR) data. Analyzing laboratory spectra of various howardite–eucrite–diogenite meteorites, high‐Ca pyroxenes, olivines, and olivine‐orthopyroxene mixtures, we derive three FC spectral band parameters that are indicators of olivine‐rich materials. Combining the three band parameters allows us, for the first time, to reliably identify sites showing modal olivine contents >40%. The olivine‐rich exposures at Bellicia and Arruntia are mapped using higher spatial resolution FC data. The exposures are located on the slopes of outer/inner crater walls, on the floor of Arruntia, in the ejecta, as well as in nearby fresh small impact craters. The spatial extent of the exposures ranges from a few hundred meters to few kilometers. The olivine‐rich exposures are in accordance with both the magma ocean and the serial magmatism model (e.g., Righter and Drake 1997 ; Yamaguchi et al. 1997 ). However, it remains unsolved why the olivine‐rich materials are mainly concentrated in the northern hemisphere (approximately 36–42°N, 46–74°E) and are almost absent in the Rheasilvia basin.