N. Tereshchenko, V. Proskurnin, O. Solov'eva, E. Tikhonova, Trong Hiep Nguyen, O. Chuzhikova-Proskurnina, I. Sidorov
Investigation of concentrations of organic and inorganic pollutants (hydrocarbons, including oil hydrocarbons, and trace elements – heavy metals and metalloids) in the Ham Luong River in the Mekong Delta was carried out and water quality was assessed by comparing the obtained levels of values with the regulatory limits of concentration. The determination of the total content of hydrocarbons and oil hydrocarbons was made by gas chromatography method; the trace elements were measured by ICP-MS technique after chemical treatment of samples. The content of oil hydrocarbons in the Ham Luong River water ranged from 0.042 to 0.076 mg/l. These values were quite high, exceeding the sanitary standard (0.05 mg/l) for fishery reservoirs, or approaching it, but they were lower compared to Vietnam national standard for domestic supply water (0.1 mg/l). The content of hydrocarbons in suspended matter was in the range of 0.011–0.37 mg/l. The concentrations of 15 trace elements were studied, nine of them (Ni, Fe, V, As, Se, Be, Cd, Sb, Tl) did not exceed any of the established regulatory limits of concentration for surface water. However, concentrations of six trace elements (Pb, Zn, Cu, Co, Ag, Mo) were found to exceed the standard regulatory limits. Among the studied 15 trace elements, critical and potentially critical elements were identified, which are subject to primary monitoring control. Chemoecological studies of water quality are important for monitoring of the ecological and sanitary water state for ensure the quality of consumed natural resources and to preserve the biological diversity of the Mekong Delta ecosystems.
{"title":"Chemoecological Monitoring of Water Quality in the Ham Luong River (Mekong Delta, Vietnam)","authors":"N. Tereshchenko, V. Proskurnin, O. Solov'eva, E. Tikhonova, Trong Hiep Nguyen, O. Chuzhikova-Proskurnina, I. Sidorov","doi":"10.2205/2023es02si05","DOIUrl":"https://doi.org/10.2205/2023es02si05","url":null,"abstract":"Investigation of concentrations of organic and inorganic pollutants (hydrocarbons, including oil hydrocarbons, and trace elements – heavy metals and metalloids) in the Ham Luong River in the Mekong Delta was carried out and water quality was assessed by comparing the obtained levels of values with the regulatory limits of concentration. The determination of the total content of hydrocarbons and oil hydrocarbons was made by gas chromatography method; the trace elements were measured by ICP-MS technique after chemical treatment of samples. The content of oil hydrocarbons in the Ham Luong River water ranged from 0.042 to 0.076 mg/l. These values were quite high, exceeding the sanitary standard (0.05 mg/l) for fishery reservoirs, or approaching it, but they were lower compared to Vietnam national standard for domestic supply water (0.1 mg/l). The content of hydrocarbons in suspended matter was in the range of 0.011–0.37 mg/l. The concentrations of 15 trace elements were studied, nine of them (Ni, Fe, V, As, Se, Be, Cd, Sb, Tl) did not exceed any of the established regulatory limits of concentration for surface water. However, concentrations of six trace elements (Pb, Zn, Cu, Co, Ag, Mo) were found to exceed the standard regulatory limits. Among the studied 15 trace elements, critical and potentially critical elements were identified, which are subject to primary monitoring control. Chemoecological studies of water quality are important for monitoring of the ecological and sanitary water state for ensure the quality of consumed natural resources and to preserve the biological diversity of the Mekong Delta ecosystems.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"11 5","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138979777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The identification of faults is a common objective in geophysical potential field methods. Vertical discontinuities such as reverse faults, also known as tectonic faults, can easily be distinguished through their effect on gravity and magnetic fields, appearing as gradient zones or areas of change in the field. However, identifying strike-slip faults is one of the biggest challenges for potential field methods as they are characterized by a complex series of anomalies with varying signs in the fault zone, as well as displacement of anomaly axes between the strike-slipped blocks. The goal of this study is to suggest a transformation that would aid in the identification of shear zones through the calculation of the displacement along the discontinuity. The proposed approach involves calculating the correlation coefficient between parallel profiles using moving windows. The position of the window with the highest calculated correlation coefficient allows estimating of the discontinuity displacement magnitude. The method was tested using a synthetic field and data from the magnetic field of the Kolbeinsi Ridge.
{"title":"Evaluation of Displacements Caused by Strike-Slip Deformations Using Correlation Characteristics Based on Potential Field Data","authors":"N. Senchina, Artem Asoskov, Gleb Gorelik","doi":"10.2205/2023es000847","DOIUrl":"https://doi.org/10.2205/2023es000847","url":null,"abstract":"The identification of faults is a common objective in geophysical potential field methods. Vertical discontinuities such as reverse faults, also known as tectonic faults, can easily be distinguished through their effect on gravity and magnetic fields, appearing as gradient zones or areas of change in the field. However, identifying strike-slip faults is one of the biggest challenges for potential field methods as they are characterized by a complex series of anomalies with varying signs in the fault zone, as well as displacement of anomaly axes between the strike-slipped blocks. The goal of this study is to suggest a transformation that would aid in the identification of shear zones through the calculation of the displacement along the discontinuity. The proposed approach involves calculating the correlation coefficient between parallel profiles using moving windows. The position of the window with the highest calculated correlation coefficient allows estimating of the discontinuity displacement magnitude. The method was tested using a synthetic field and data from the magnetic field of the Kolbeinsi Ridge.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"53 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139335446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper presents analysis of intra-centennial (inter-decadal and multidecadal) variations of the length of day (LOD) and some oceanic parameters such as sea surface temperature (SST) and sea level (SL). Methods of multivariate regression analysis and correlation analysis are used. Results of the regression analysis show a spatially coherent response of SST to LOD variations on the multidecadal time scale. The earlier response is peculiar to the north and tropical Atlantic where the multidecadal SST variations are approximately opposite to the LOD variations. In the most remaining parts of the oceans, except especially in the Nino 3.4 region of the equatorial east Pacific, the multidecadal SST variations are generally lagged relative to the antiphase variations of the LOD. Smoothing of SST averaged over different areas and of the global mean SL shows that the intra-annual variations include inter-decadal, 20–30-year, multidecadal, 60–70-year, components that correspond to similar oscillation components in the LOD. The most striking correspondence of the two components is observed between the LOD and SST averaged over the Nino 3.4 region. Generally, there are significant correlations of the intra-centennial variations on the averaged and smoothed SST series and global mean SL with the LOD variations. We propose that angular momentum exchange processes involving oceanic circulation and interactions between the Earth’s core and the mantle play probably a part in the observed relationships of intra-centennial variations in oceanic parameters with variations in the LOD.
{"title":"Consistency of Intra-Centennial Oscillations in Length of Day and Oceanic Characteristics","authors":"Viacheslav Bezverhniy, Aleksandr Gruzdev","doi":"10.2205/2023es000842","DOIUrl":"https://doi.org/10.2205/2023es000842","url":null,"abstract":"The paper presents analysis of intra-centennial (inter-decadal and multidecadal) variations of the length of day (LOD) and some oceanic parameters such as sea surface temperature (SST) and sea level (SL). Methods of multivariate regression analysis and correlation analysis are used. Results of the regression analysis show a spatially coherent response of SST to LOD variations on the multidecadal time scale. The earlier response is peculiar to the north and tropical Atlantic where the multidecadal SST variations are approximately opposite to the LOD variations. In the most remaining parts of the oceans, except especially in the Nino 3.4 region of the equatorial east Pacific, the multidecadal SST variations are generally lagged relative to the antiphase variations of the LOD. Smoothing of SST averaged over different areas and of the global mean SL shows that the intra-annual variations include inter-decadal, 20–30-year, multidecadal, 60–70-year, components that correspond to similar oscillation components in the LOD. The most striking correspondence of the two components is observed between the LOD and SST averaged over the Nino 3.4 region. Generally, there are significant correlations of the intra-centennial variations on the averaged and smoothed SST series and global mean SL with the LOD variations. We propose that angular momentum exchange processes involving oceanic circulation and interactions between the Earth’s core and the mantle play probably a part in the observed relationships of intra-centennial variations in oceanic parameters with variations in the LOD.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135579917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In 2023, monitoring geophysical studies were carried out using the electrical resistivity tomography (ERT) method along three profiles that cross the strike zone of the Issyk-Ata fault in the transverse direction. A detailed study was carried out of the observed variations in apparent electrical resistivity, which characterize the change in the electrical properties of the upper part of the Earth's crust section with a 40-minute discretization in time. Using the analysis of difference pseudo-sections of apparent resistivity, constructed based on the results of ERT monitoring, the most informative pseudo-depth interval from the point of view of geoelectric activity was determined for all three monitoring profiles. Accordingly, for a pseudo-depth of 24 m on each monitoring profile, an assessment was made of the geodynamic activity of these sections of the Issyk-Ata fault based on an analysis of the magnitude of two parameters: the amplitude of apparent resistivity variations and the correlation coefficient of electrical resistivity variations with lunar-solar solid tides. High values of these parameters, in our opinion, determine the location of modern active fault zones.
{"title":"Studies of the Electrical Resistivity Tomography Monitoring of the Issyk-Ata Fault Zone (Northern Tien Shan)","authors":"A. Rybin, E. Bataleva, O. Zabinyakova, K. Nepeina","doi":"10.2205/2023es000881","DOIUrl":"https://doi.org/10.2205/2023es000881","url":null,"abstract":"In 2023, monitoring geophysical studies were carried out using the electrical resistivity tomography (ERT) method along three profiles that cross the strike zone of the Issyk-Ata fault in the transverse direction. A detailed study was carried out of the observed variations in apparent electrical resistivity, which characterize the change in the electrical properties of the upper part of the Earth's crust section with a 40-minute discretization in time. Using the analysis of difference pseudo-sections of apparent resistivity, constructed based on the results of ERT monitoring, the most informative pseudo-depth interval from the point of view of geoelectric activity was determined for all three monitoring profiles. Accordingly, for a pseudo-depth of 24 m on each monitoring profile, an assessment was made of the geodynamic activity of these sections of the Issyk-Ata fault based on an analysis of the magnitude of two parameters: the amplitude of apparent resistivity variations and the correlation coefficient of electrical resistivity variations with lunar-solar solid tides. High values of these parameters, in our opinion, determine the location of modern active fault zones.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"38 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139335684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rashid Baymuratov, Maksim Napreenko, Yuliya Koroleva
The paper provides original data on accumulation capabilities of bryophytes typical of peatland ecosystems with different degree of anthropogenic transformation occurring in the Kaliningrad Region of Russia. A key study area was the Vittgirrensky Peatland, abandoned after milled peat extraction in 1990s and designated as the Rossyanka Carbon Measurement Supersite in 2021. The accumulation of micro- and macroelements: Ca, Mn, Fe, Ni, Zn, Br, Rb, and Sr – was identified by means of X-ray fluorescence spectroscopy in 13 bryophyte species (Aulacomnium palustre, Campylopus introflexus, Polytrichum commune, P. strictum, Sphagnum capillifolium, S. centrale, S. cuspidatum, S. fuscum, S. magellanicum, S. riparium, S. squarrosum, S. teres) focusing on comparison with the reference species Pleurozium schreberi. The records of average element concentrations from the Vittgirrensky Peatland are shown to be distinctly lower than the regional background level. The accumulation of Mn, Ni, Br, Rb, and Sr varies significantly among disturbed and natural sites: the concentrations are comparable for Fe and Zn, while cut-over peatlands showed the level of Mn several times less than in undisturbed peat bogs. Aulacomnium palustre can be recommended for passive biomonitoring purposes on bog ecosystems as having most similar accumulation capability to the reference species Pleurozium schreberi that is widely recognized as indicator of atmospheric air pollution.
本文提供了俄罗斯加里宁格勒地区不同人为改造程度泥炭地生态系统典型苔藓植物积累能力的原始资料。Vittgirrensky泥炭地是一个重要的研究区域，该地区在20世纪90年代进行了泥炭开采后被废弃，并于2021年被指定为Rossyanka碳测量超级地点。采用x射线荧光光谱法测定了13种苔藓植物(Aulacomnium palustre, Campylopus introflexus, Polytrichum commune, P. strictum, Sphagnum capillifolium, S. centrale, S. cuspidatum, S. fuscum, S. magellanicum, S. riparium, S. squarrosum, S. teres)中微量元素Ca, Mn, Fe, Ni, Zn, Br, Rb和Sr -)的积累量，并与参比种Pleurozium schreberi进行了比较。维特吉伦斯基泥炭地的平均元素浓度记录明显低于区域背景水平。Mn、Ni、Br、Rb和Sr的积累在受干扰的地点和自然地点之间差异显著:铁和锌的浓度相当，而切割泥炭地的Mn水平比未受干扰的泥炭沼泽低几倍。palustre与参考物种schreberi Pleurozium schreberi具有最相似的积累能力，被广泛认为是大气污染的指标，因此可以推荐用于沼泽生态系统的被动生物监测。
{"title":"Accumulation Characteristics of Bryophytes in Abandoned Disturbed Peatlands: A Case Study From the Kaliningrad Region, Russia","authors":"Rashid Baymuratov, Maksim Napreenko, Yuliya Koroleva","doi":"10.2205/2023es000873","DOIUrl":"https://doi.org/10.2205/2023es000873","url":null,"abstract":"The paper provides original data on accumulation capabilities of bryophytes typical of peatland ecosystems with different degree of anthropogenic transformation occurring in the Kaliningrad Region of Russia. A key study area was the Vittgirrensky Peatland, abandoned after milled peat extraction in 1990s and designated as the Rossyanka Carbon Measurement Supersite in 2021. The accumulation of micro- and macroelements: Ca, Mn, Fe, Ni, Zn, Br, Rb, and Sr – was identified by means of X-ray fluorescence spectroscopy in 13 bryophyte species (Aulacomnium palustre, Campylopus introflexus, Polytrichum commune, P. strictum, Sphagnum capillifolium, S. centrale, S. cuspidatum, S. fuscum, S. magellanicum, S. riparium, S. squarrosum, S. teres) focusing on comparison with the reference species Pleurozium schreberi. The records of average element concentrations from the Vittgirrensky Peatland are shown to be distinctly lower than the regional background level. The accumulation of Mn, Ni, Br, Rb, and Sr varies significantly among disturbed and natural sites: the concentrations are comparable for Fe and Zn, while cut-over peatlands showed the level of Mn several times less than in undisturbed peat bogs. Aulacomnium palustre can be recommended for passive biomonitoring purposes on bog ecosystems as having most similar accumulation capability to the reference species Pleurozium schreberi that is widely recognized as indicator of atmospheric air pollution.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135585949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article examines the scientific achievements of the editor-in-chief of the Russian Journal of Earth Sciences, Academician of the Russian Academy of Sciences (RAS) Alexei Gvishiani, and his contribution to the field of geophysics and systems analysis. Alexei is a prominent representative of the academic community, his role in the work of the RAS is shown. His scientific works and leadership qualities made significant contributions to the development of geophysics, for which he was awarded many awards and titles. His contributions to science have been widely recognized by the international academic community. The article also highlights the activities of A. Gvishiani as an outstanding organizer of science, which was carried out throughout almost all of his work at the Russian Academy of Sciences.
{"title":"Congratulations on the 75th Anniversary of Alexei Gvishiani","authors":"Ernest Kedrov","doi":"10.2205/2023es0004","DOIUrl":"https://doi.org/10.2205/2023es0004","url":null,"abstract":"This article examines the scientific achievements of the editor-in-chief of the Russian Journal of Earth Sciences, Academician of the Russian Academy of Sciences (RAS) Alexei Gvishiani, and his contribution to the field of geophysics and systems analysis. Alexei is a prominent representative of the academic community, his role in the work of the RAS is shown. His scientific works and leadership qualities made significant contributions to the development of geophysics, for which he was awarded many awards and titles. His contributions to science have been widely recognized by the international academic community. The article also highlights the activities of A. Gvishiani as an outstanding organizer of science, which was carried out throughout almost all of his work at the Russian Academy of Sciences.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134903905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Statistical modeling of the Don River solid runoff based on water discharge and turbidity measurements obtained at the hydrological station in the village of Razdorskaya for the twelve-year period 2009–2020 was carried out. The WRTDS (Weighted Regressions on Time, Discharge, and Season) and WRTDSKalman (WRTDS with Kalman filtering) methods were applied. The developed statistical model is aimed at solving the problem of the imbalance between the regularity of collecting data on water discharge and data on the concentration of suspended matter by “restoring” the concentration values on days without measurements based on data on the most “similar” days with measurements in terms of time, discharge and season and does not claim to describe a relationship between the concentration of the constituent of interest and discharge. The quality of the developed statistical model and its modification were checked. The average daily concentrations and fluxes of suspended matter were compared with estimates of the volumes of suspended material deposited during periods of recurring strong surge phenomena. A comparative assessment of sea and river factors contributions to the transport and sedimentation of suspended matter in the Don River delta was fulfilled.
{"title":"Solid runoff of the Don River and suspended matter flow into the delta during surges: statistical modeling and comparison in the low water period","authors":"Nataliya Likhtanskaya, Sergey Berdnikov, Alexey Kleshchenkov","doi":"10.2205/2023es000856","DOIUrl":"https://doi.org/10.2205/2023es000856","url":null,"abstract":"Statistical modeling of the Don River solid runoff based on water discharge and turbidity measurements obtained at the hydrological station in the village of Razdorskaya for the twelve-year period 2009–2020 was carried out. The WRTDS (Weighted Regressions on Time, Discharge, and Season) and WRTDSKalman (WRTDS with Kalman filtering) methods were applied. The developed statistical model is aimed at solving the problem of the imbalance between the regularity of collecting data on water discharge and data on the concentration of suspended matter by “restoring” the concentration values on days without measurements based on data on the most “similar” days with measurements in terms of time, discharge and season and does not claim to describe a relationship between the concentration of the constituent of interest and discharge. The quality of the developed statistical model and its modification were checked. The average daily concentrations and fluxes of suspended matter were compared with estimates of the volumes of suspended material deposited during periods of recurring strong surge phenomena. A comparative assessment of sea and river factors contributions to the transport and sedimentation of suspended matter in the Don River delta was fulfilled.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"36 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139335348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We consider Bloch eigenmodes of three linear stability problems: the kinematic dynamo problem, the hydrodynamic and MHD stability problem for steady space-periodic flows and MHD states comprised of randomly generated Fourier coefficients and having energy spectra of three types: exponentially decaying, Kolmogorov with a cut off, or involving a small number of harmonics (“big eddies”). A Bloch mode is a product of a field of the same periodicity as the perturbed state and a planar harmonic wave, exp(iq · x). Such a mode is characterized by the ratio of spatial scales which, for simplicity, we identify with the length |q| < 1 of the Bloch wave vector q. Computations have revealed that the Bloch modes, whose growth rates are maximum over q, feature the scale ratio that decreases on increasing the nondimensionalized molecular diffusivity and/or viscosity from 0.03 to 0.3, and the scale separation is high (i.e., |q| is small) only for large molecular diffusivities. Largely this conclusion holds for all the three stability problems and all the three energy spectra types under consideration. Thus, in a natural MHD system not affected by strong diffusion, a given scale range gives rise to perturbations involving only moderately larger spatial scales (i.e., |q| only moderately small), and the MHD evolution consists of a cascade of processes, each generating a slightly larger spatial scale; flows or magnetic fields characterized by a high scale separation are not produced. This cascade is unlikely to be amenable to a linear description. Consequently, our results question the allegedly high role of the α-effect and eddy diffusivity that are based on spatial scale separation, as the primary instability or magnetic field generating mechanisms in astrophysical applications. The Braginskii magnetic α-effect in a weakly non-axisymmetric flow, often used for explanation of the solar and geodynamo, is advantageous not being upset by a similar deficiency.
{"title":"Linear perturbations of the Bloch type of space-periodic magnetohydrodynamic steady states. II. Numerical results","authors":"R Chertovskih, V Zheligovsky","doi":"10.2205/2023es000838","DOIUrl":"https://doi.org/10.2205/2023es000838","url":null,"abstract":"We consider Bloch eigenmodes of three linear stability problems: the kinematic dynamo problem, the hydrodynamic and MHD stability problem for steady space-periodic flows and MHD states comprised of randomly generated Fourier coefficients and having energy spectra of three types: exponentially decaying, Kolmogorov with a cut off, or involving a small number of harmonics (“big eddies”). A Bloch mode is a product of a field of the same periodicity as the perturbed state and a planar harmonic wave, exp(iq · x). Such a mode is characterized by the ratio of spatial scales which, for simplicity, we identify with the length |q| < 1 of the Bloch wave vector q. Computations have revealed that the Bloch modes, whose growth rates are maximum over q, feature the scale ratio that decreases on increasing the nondimensionalized molecular diffusivity and/or viscosity from 0.03 to 0.3, and the scale separation is high (i.e., |q| is small) only for large molecular diffusivities. Largely this conclusion holds for all the three stability problems and all the three energy spectra types under consideration. Thus, in a natural MHD system not affected by strong diffusion, a given scale range gives rise to perturbations involving only moderately larger spatial scales (i.e., |q| only moderately small), and the MHD evolution consists of a cascade of processes, each generating a slightly larger spatial scale; flows or magnetic fields characterized by a high scale separation are not produced. This cascade is unlikely to be amenable to a linear description. Consequently, our results question the allegedly high role of the α-effect and eddy diffusivity that are based on spatial scale separation, as the primary instability or magnetic field generating mechanisms in astrophysical applications. The Braginskii magnetic α-effect in a weakly non-axisymmetric flow, often used for explanation of the solar and geodynamo, is advantageous not being upset by a similar deficiency.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"2011 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134903176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Baikal Rift Zone is seismically active and each well recorded strong earthquake (for example, as the Kultukskoe earthquake (South of Baikal), on August 27, 2008, with Mw = 6.3) is the reason to refine existing models for seismic hazard estimates. There are several approaches to study strong ground motion, and one of them is to model synthetic accelerograms to reconstruct the rupture process. In this paper we are mostly interested in calculating accelerograms for the city of Irkutsk, considering source spectra with two corner frequencies, primarily, to reconstruct impact from the Kultukskoe earthquake.
{"title":"Modeling of Strong Ground Motion Within the Baikal Rift Zone: The Irkutsk Case","authors":"Anna Skorkina","doi":"10.2205/2023es000823","DOIUrl":"https://doi.org/10.2205/2023es000823","url":null,"abstract":"The Baikal Rift Zone is seismically active and each well recorded strong earthquake (for example, as the Kultukskoe earthquake (South of Baikal), on August 27, 2008, with Mw = 6.3) is the reason to refine existing models for seismic hazard estimates. There are several approaches to study strong ground motion, and one of them is to model synthetic accelerograms to reconstruct the rupture process. In this paper we are mostly interested in calculating accelerograms for the city of Irkutsk, considering source spectra with two corner frequencies, primarily, to reconstruct impact from the Kultukskoe earthquake.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134904037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eugene Morozov, P Zavialov, V Zamshin, O Moller, D Frey, Oleg Zuev, Anna Seliverstova, Alexey Bulanov, Nadezhda Lipinskaya, Pavel Salyuk, Olga Chvertkova, Inna Nemirovskaya, Viktor Krechik, Anna Chultsova
Results of a joint Russian-Brazilian expedition to study the dynamics of continental river runoff in the ocean associated with the Amazon plume are presented. The stations of the study region covered the seaward part of the Amazon plume. The work was carried out in the dry season (November). The data of in situ measurements and satellite data show that the most desalinated and rich in suspended particulate matter and chlorophyll-a waters were localized on the shallow inner shelf. The horizontal and vertical structure of the thermohaline fields indicates the presence of a well-pronounced river plume about 15 m thick. The decrease in salinity in the plume relative to the background values exceeded 6 PSU even at 300–400 km from the river mouth. The plume waters were characterized by increased concentrations of suspended matter. The best approximation to the in situ measurements is provided by the SMOS satellite salinity data and reanalysis GLORYS12. Chemical determinations in the surface layer in the area of the plume reveal elevated concentrations of silicates, phosphates, and nitrites compared to the seaward part.
{"title":"Spreading of the Amazon River Plume","authors":"Eugene Morozov, P Zavialov, V Zamshin, O Moller, D Frey, Oleg Zuev, Anna Seliverstova, Alexey Bulanov, Nadezhda Lipinskaya, Pavel Salyuk, Olga Chvertkova, Inna Nemirovskaya, Viktor Krechik, Anna Chultsova","doi":"10.2205/2023es000863","DOIUrl":"https://doi.org/10.2205/2023es000863","url":null,"abstract":"Results of a joint Russian-Brazilian expedition to study the dynamics of continental river runoff in the ocean associated with the Amazon plume are presented. The stations of the study region covered the seaward part of the Amazon plume. The work was carried out in the dry season (November). The data of in situ measurements and satellite data show that the most desalinated and rich in suspended particulate matter and chlorophyll-a waters were localized on the shallow inner shelf. The horizontal and vertical structure of the thermohaline fields indicates the presence of a well-pronounced river plume about 15 m thick. The decrease in salinity in the plume relative to the background values exceeded 6 PSU even at 300–400 km from the river mouth. The plume waters were characterized by increased concentrations of suspended matter. The best approximation to the in situ measurements is provided by the SMOS satellite salinity data and reanalysis GLORYS12. Chemical determinations in the surface layer in the area of the plume reveal elevated concentrations of silicates, phosphates, and nitrites compared to the seaward part.","PeriodicalId":44680,"journal":{"name":"Russian Journal of Earth Sciences","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134904343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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