Variety Of Ground Research Articles

SN 2021zny: an early flux excess combined with late-time oxygen emission suggests a double white dwarf merger event

ABSTRACT We present a photometric and spectroscopic analysis of the ultraluminous and slowly evolving 03fg-like Type Ia SN 2021zny. Our observational campaign starts from ∼5.3 h after explosion (making SN 2021zny one of the earliest observed members of its class), with dense multiwavelength coverage from a variety of ground- and space-based telescopes, and is concluded with a nebular spectrum ∼10 months after peak brightness. SN 2021zny displayed several characteristics of its class, such as the peak brightness (MB = −19.95 mag), the slow decline (Δm15(B) = 0.62 mag), the blue early-time colours, the low ejecta velocities, and the presence of significant unburned material above the photosphere. However, a flux excess for the first ∼1.5 d after explosion is observed in four photometric bands, making SN 2021zny the third 03fg-like event with this distinct behaviour, while its +313 d spectrum shows prominent [O i] lines, a very unusual characteristic of thermonuclear SNe. The early flux excess can be explained as the outcome of the interaction of the ejecta with $\sim 0.04\, \mathrm{M_{\odot }}$ of H/He-poor circumstellar material at a distance of ∼1012 cm, while the low ionization state of the late-time spectrum reveals low abundances of stable iron-peak elements. All our observations are in accordance with a progenitor system of two carbon/oxygen white dwarfs that undergo a merger event, with the disrupted white dwarf ejecting carbon-rich circumstellar material prior to the primary white dwarf detonation.

Electromagnetic pinned solitons for space debris detection

Electromagnetic “pinned” solitons in the form of stationary nonlinear waves are studied within the framework of an inertial magneto-hydrodynamic model. These structures, that can arise when a charged source moves in a magnetized plasma, have a velocity that is equal to the source velocity and, hence, appear as “pinned” structures that envelope the source. We investigate the excitation of such solitons in the Low Earth Orbit region due to the passage of charged orbital debris objects. The spatial size of these electromagnetic solitons, typically of the order of a few ion skin depths, can be very large in this region. Such solitons can be detected using a variety of ground- or orbit-based radio sounding techniques and may provide a convenient additional means of tracking small sized orbital debris objects that are difficult to spot optically.

Геоинформационное моделирование экосистем на основе бассейнового подхода

The basin approach is an effective tool for the organization and administration of environmental management at the regional and interregional levels. Statistical processing of basin information makes it possible to comprehensively assess the ecology of river catchment areas of different hierarchical levels. Assessing the state of unique natural characteristics for each basin and identifying relationships between them is a complex task that requires the use of various methods and technologies of geoinformation modeling using a variety of ground and satellite data. The elementary territorial unit in this work is the minimum watersheds of the pilot area of four watersheds in Eastern Siberia with an average area of about 1 ha. For each basin, a set of attributes of unique natural characteristics is formed, which are obtained on the basis of ground-based research and satellite data, as well as climate models. Such a set of attributes makes it possible to assess the state of the territory based on various methods of mathematical modeling, statistical and cluster analysis. Basin modeling of the territory was performed on the basis of a hydrologically correct digital relief model MERIT DEM Hydro. Based on Terra/MODIS satellite information, data on temperature, vegetation indices, and vegetation cover were obtained for each catchment area. According to the data of the NASA GPM and NCEP GFS reanalysis, data on accumulated precipitation were generated for all elementary watersheds. An analysis of the seasonal dynamics of surface temperature in the study area was carried out, and statistical distributions of changes in surface temperature during the year were obtained for each watershed. The sum of active air temperatures above 10°C was calculated. Statistical values and average annual characteristics of trends in the vegetation indices NDVI, SAVI and LAI for each basin were obtained. The created geoinformation model is a tool for ensuring the tasks of assessing the state of ecosystems based on the landscape-basin approach. The necessary methods and technologies for creating, storing and processing data for each watershed have been developed.

Emission, transport, deposition, chemical and radiative impacts of mineral dust during severe dust storm periods in March 2021 over East Asia

A Regional Air Quality Model System (named RAQMS) coupled with a developed dust model driven by WRF was applied to synthetically investigate the emission, transport, deposition, budget, and chemical and radiative effects of mineral dust during the severe dust storm periods of 10–31 March 2021. Model results were validated against a variety of ground, vertical and satellite observations, which demonstrated a generally good model ability in reproducing meteorological variables, particulate matter and compositions, and aerosol optical properties. The first dust storm (DS1), which was the severest one since 2010 was originated from the Gobi Desert in southern Mongolia on 14 March, with the dust emission flux reaching 2785 μg m−2 s−1 and the maximum dust concentration exceeding 18,000 μg m−3 in the dust deflation region. This dust storm resulted in remarkably high hourly PM10 observations up to 7506 μg m−3, 1887 μg m−3, and 2704 μg m−3 in Beijing, Tianjin, and Shijiazhuang on 15 March, respectively, and led to a maximum decrease in surface shortwave radiation up to 313.4 W m−2 (72 %) in Beijing. The second dust storm (DS2) broke out in the deserts of eastern Mongolia, with lower dust emission than the first one. The extinction of shortwave radiation by dust aerosols led to a reduction in photolysis rate and consequently decreases in O3 and secondary aerosol concentrations over the North China Plain (NCP), whereas total sulfate and nitrate concentrations consistently increased due to heterogeneous reactions on dust surfaces over the middle reaches of the Yellow River and the NCP region during DS1. Sulfate and nitrate formation through heterogeneous reactions were enhanced in the dust backflow on 16–17 March by approximately 18 % and 24 % on average in the NCP. Heterogeneous reactions and photolysis rate reduction by mineral dust jointly led to average changes in sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) concentrations by 13.0 %, 13.5 %, −12.3 %, and −4.4 %, respectively, in the NCP region during DS1, larger than the changes in the Yangtze River Delta (YRD). The maximum dry deposition settled in the 7–11 μm size range in downwind land and ocean areas, while wet deposition peaked in the 4.7–7 μm size range in the entire domain. Wet deposition was approximately twice the dry deposition over mainland China except for dust source regions. During 10–31 March, the total dust emission, dry and wet depositions were estimated to be 31.4 Tg, 13.78 Tg and 4.75 Tg, respectively, with remaining 12.87 Tg of dust aerosols (41 % of the dust emission) suspending in the atmosphere or transporting to other continents and oceans.

Direct and indirect effects and feedbacks of biomass burning aerosols over Mainland Southeast Asia and South China in springtime

Southeast Asia is one of the largest biomass burning (BB) source regions in the world. In order to promote our understanding of BB aerosol characteristics and environmental impacts, this study investigated the emission, composition, evolution, radiative effects, and feedbacks of BB aerosols from Mainland Southeast Asia during 15 March to 15 April 2019 by using an online-coupled regional chemistry/aerosol-climate model RIEMS-Chem. Model results are compared against a variety of ground and vertical observations, indicating a generally good model performance for meteorology, aerosol chemical compositions, and aerosol optical properties. It is found that BB aerosols contributed significantly to regional particulate matter (PM), accounting for up to 90 % of the near-surface PM2.5, BC, and OC concentrations over the BB source regions of north Mainland Southeast Asia and for approximately 30–70 % over wide downwind areas including most areas of southwest China and portions of south China. At the top of atmosphere (TOA), BB aerosols exerted a positive all-sky radiative effect (DREBB) up to 25 W/m2 over north Vietnam and south China, a negative DREBB up to −10 W/m2 over Myanmar, western Thailand, and southwest China. Meanwhile, the indirect radiative effect (IREBB) was consistently negative, with the maximum of −10 W/m2 over downwind areas with cloud coverage, e.g., from north Vietnam to most of south China. The subregional (95–125°E and 10–30°N) and period mean DREBB and IREBB at TOA were estimated to be 0.69 W/m2 and − 0.63 W/m2, respectively, leading a total radiative effect (TREBB) of 0.06 W/m2 at TOA. The radiative effects of BB aerosols led to decreases in sensible and latent heat fluxes, near-surface temperature, PBL height, and wind speed of 6.0 Wm−2, 9.0 Wm−2, 0.26 °C, 38.7 m, and 0.1 m/s, respectively, accompanied with an increase in RH of 1.9 %, averaged over the subregion and the study period. The accumulated precipitation during the study period was apparently reduced by BB aerosols from east Thailand to south China, with the maximum reduction up to 14 cm (exceeding 40 %) over north Vietnam and south China. TREBB tended to increase mean near-surface PM2.5 and its component concentrations, with the maximum percentage increase up to 24 % over the BB source regions of north Mainland Southeast Asia, resulting from the combined effects of dynamic and chemical feedbacks. DREBB generally dominated over IREBB in the feedback-induced PM2.5 concentration changes.

A Carbon/Oxygen-dominated Atmosphere Days after Explosion for the “Super-Chandrasekhar” Type Ia SN 2020esm

Abstract Seeing pristine material from the donor star in a type Ia supernova (SN Ia) explosion can reveal the nature of the binary system. In this paper, we present photometric and spectroscopic observations of SN 2020esm, one of the best-studied SNe of the class of “super-Chandrasekhar” SNe Ia (SC SNe Ia), with data obtained −12 to +360 days relative to peak brightness, obtained from a variety of ground- and space-based telescopes. Initially misclassified as a type II supernova, SN 2020esm peaked at M B = −19.9 mag, declined slowly (Δm 15(B) = 0.92 mag), and had particularly blue UV and optical colors at early times. Photometrically and spectroscopically, SN 2020esm evolved similarly to other SC SNe Ia, showing the usual low ejecta velocities, weak intermediate-mass elements, and the enhanced fading at late times, but its early spectra are unique. Our first few spectra (corresponding to a phase of ≳10 days before peak) reveal a nearly pure carbon/oxygen atmosphere during the first days after explosion. This composition can only be produced by pristine material, relatively unaffected by nuclear burning. The lack of H and He may further indicate that SN 2020esm is the outcome of the merger of two carbon/oxygen white dwarfs. Modeling its bolometric light curve, we find an 56Ni mass of 1.23 − 0.14 + 0.14 M ☉ and an ejecta mass of 1.75 − 0.20 + 0.32 M ☉, in excess of the Chandrasekhar mass. Finally, we discuss possible progenitor systems and explosion mechanisms of SN 2020esm and, in general, the SC SNe Ia class.

Improved Resolution and Cost Performance of Low-Cost MEMS Seismic Sensor through Parallel Acquisition.

In earthquake monitoring, an important aspect of the operational effect of earthquake intensity rapid reporting and earthquake early warning networks depends on the density and performance of the deployed seismic sensors. To improve the resolution of seismic sensors as much as possible while keeping costs low, in this article the use of multiple low-cost and low-resolution digital MEMS accelerometers is proposed to increase the resolution through the correlation average method. In addition, a cost-effective MEMS seismic sensor is developed. With ARM and Linux embedded computer technology, this instrument can cyclically store the continuous collected data on a built-in large-capacity SD card for approximately 12 months. With its real-time seismic data processing algorithm, this instrument is able to automatically identify seismic events and calculate ground motion parameters. Moreover, the instrument is easy to install in a variety of ground or building conditions. The results show that the RMS noise of the instrument is reduced from 0.096 cm/s2 with a single MEMS accelerometer to 0.034 cm/s2 in a bandwidth of 0.1–20 Hz by using the correlation average method of eight low-cost MEMS accelerometers. The dynamic range reaches more than 90 dB, the amplitude–frequency response of its input and output within −3 dB is DC −80 Hz, and the linearity is better than 0.47%. In the records from our instrument, earthquakes with magnitudes between M2.2 and M5.1 and distances from the epicenter shorter than 200 km have a relatively high SNR, and are more visible than they were prior to the joint averaging.

A Multi-Sensor Approach for Volcanic Ash Cloud Retrieval and Eruption Characterization: The 23 November 2013 Etna Lava Fountain

Volcanic activity is observed worldwide with a variety of ground and space-based remote sensing instruments, each with advantages and drawbacks. No single system can give a comprehensive description of eruptive activity, and so, a multi-sensor approach is required. This work integrates infrared and microwave volcanic ash retrievals obtained from the geostationary Meteosat Second Generation (MSG)-Spinning Enhanced Visible and Infrared Imager (SEVIRI), the polar-orbiting Aqua-MODIS and ground-based weather radar. The expected outcomes are improvements in satellite volcanic ash cloud retrieval (altitude, mass, aerosol optical depth and effective radius), the generation of new satellite products (ash concentration and particle number density in the thermal infrared) and better characterization of volcanic eruptions (plume altitude, total ash mass erupted and particle number density from thermal infrared to microwave). This approach is the core of the multi-platform volcanic ash cloud estimation procedure being developed within the European FP7-APhoRISM project. The Mt. Etna (Sicily, Italy) volcano lava fountaining event of 23 November 2013 was considered as a test case. The results of the integration show the presence of two volcanic cloud layers at different altitudes. The improvement of the volcanic ash cloud altitude leads to a mean difference between the SEVIRI ash mass estimations, before and after the integration, of about the 30%. Moreover, the percentage of the airborne “fine” ash retrieved from the satellite is estimated to be about 1%–2% of the total ash emitted during the eruption. Finally, all of the estimated parameters (volcanic ash cloud altitude, thickness and total mass) were also validated with ground-based visible camera measurements, HYSPLIT forward trajectories, Infrared Atmospheric Sounding Interferometer (IASI) satellite data and tephra deposits.

A SUNYAEV-ZEL'DOVICH-SELECTED SAMPLE OF THE MOST MASSIVE GALAXY CLUSTERS IN THE 2500 deg2SOUTH POLE TELESCOPE SURVEY

The South Pole Telescope (SPT) is currently surveying 2500 deg^2 of the southern sky to detect massive galaxy clusters out to the epoch of their formation using the Sunyaev-Zel'dovich (SZ) effect. This paper presents a catalog of the 26 most significant SZ cluster detections in the full survey region. The catalog includes 14 clusters which have been previously identified and 12 that are new discoveries. These clusters were identified in fields observed to two differing noise depths: 1500 deg^2 at the final SPT survey depth of 18 uK-arcmin at 150 GHz, and 1000 deg^2 at a depth of 54 uK-arcmin. Clusters were selected on the basis of their SZ signal-to-noise ratio (S/N) in SPT maps, a quantity which has been demonstrated to correlate tightly with cluster mass. The S/N thresholds were chosen to achieve a comparable mass selection across survey fields of both depths. Cluster redshifts were obtained with optical and infrared imaging and spectroscopy from a variety of ground- and space-based facilities. The redshifts range from 0.098 \leq z \leq 1.132 with a median of z_med = 0.40. The measured SZ S/N and redshifts lead to unbiased mass estimates ranging from 9.8 \times 10^14 M_sun/h_70 \leq M_200(rho_mean) \leq 3.1 \times 10^15 M_sun/h_70. Based on the SZ mass estimates, we find that none of the clusters are individually in significant tension with the LambdaCDM cosmological model. We also test for evidence of non-Gaussianity based on the cluster sample and find the data show no preference for non-Gaussian perturbations.

Examples of open caisson sinking in Scotland

Open caisson-sinking techniques permit a shaft structure to be progressively sunk, either under its own weight or with the aid of caisson jacks, in a controlled manner from the surface to a predetermined depth. The technique is suited to shaft construction through weak soils, high- to extremely high-plasticity clays, silts, and sands and gravels, particularly below the water table. In the tunnelling and public works engineering sectors, open caissons are typically circular in cross-section; those used in harbour works are commonly square or rectangular in plan. The paper briefly describes the components and method of sinking dry and wet open caissons, highlighting good practice. It then examines in detail four recent, highly successful caisson-sinking operations carried out under a framework agreement for Scottish Water Solutions in their wastewater treatment works at Crianlarich, Doune, Killearn and Drymen. Although modest in size, each contractor-designed caisson was sunk through a variety of ground and water conditions, illustrating the versatility of the technique and its advantages over more conventional methods of shallow-depth shaft construction. The importance of a comprehensive site investigation programme and the control measures required to satisfy verticality and structural integrity requirements are discussed. The paper concludes with a series of practical guidelines designed to assist those contemplating using the technique, and to remind practitioners of good caisson-sinking practice.

Development of freshwater water-quality criteria for perchlorate.

The anion perchlorate (ClO4-) is an oxidizing component commonly used in solid propellants for rockets and missiles; in explosives, flares, fireworks, chemical processes, and automobile air-bag inflators; and for other assorted uses. With recent advances in analytical detection capability, perchlorate has been found in a variety of ground and surface waters throughout the United States. Because perchlorate has been associated with thyroid problems in humans and may have similar effects on wildlife, it is desirable to develop a water-quality criterion to assist in identifying concentrations of perchlorate in water likely to pose an ecological health risk. In the present study, we compiled all available data regarding the effects of perchlorate to aquatic organisms, and we performed additional toxicity and bioconcentration tests as required by the U.S. Environmental Protection Agency (U.S. EPA) for the development of water-quality criteria for aquatic life. A criterion maximum concentration of 20 mg/L and a criterion continuous concentration of 9.3 mg/L were calculated based on the test results. Although these are not formal Clean Water Act Section 304(a) criteria, which must be published by the U.S. EPA, these criteria may be useful in the determination of remedial action levels for contaminated sites, for National Pollutant Discharge Elimination System permit limits, and other water-quality management practices.

Three Springs Talc Mine: A new view on an old deposit

A successful application of the high resolution seismic reflection method for talc exploration, is demonstrated using an experimental seismic line, recorded over the Three Springs talc deposit. Since 1973, a variety of ground and airborne geophysical techniques had been applied to talc exploration at Three Springs, with limited success. However, wireline logging and laboratory petrophysical measurements have provided new insights into the physical properties of talc and contrasts between talc and adjacent dolomite and dolerite rocks. In particular, P-wave velocity measurements demonstrated that the elastic contrast between the talc mineralisation and surrounding rocks may be sufficient for the application of seismic reflection methods to talc exploration. Between 1989 and 1993, seismic reflection and refraction surveys were acquired on a single profile across the Three Springs talc deposit. The results of this work were disappointing, apparently contradicting physical property measurements. Greatly improved results from re-processing of the `old? seismic data, in 2000, suggested seismic reflection may indeed assist in mapping of the talc mineralisation, as well as providing important detailed structural information. Additional experimental data acquisition, undertaken in 2000, confirmed the potential application of the seismic reflection method to deposit ? scale talc exploration. However, whether the seismic technique can be routinely applied, in a cost ? effective manner, providing the required geological detail, remains to be seen.

Spatial patterns of soil moisture for the FIFE study area derived from remotely sensed and ground data

Soil moisture observations were made over the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) study area in 1987 and 1989 using a variety of ground and airborne techniques. A procedure is described for deriving spatial patterns of soil moisture by combining these different data types. The spatial patterns of soil moisture are represented as both contour and grid values so that they can be readily incorporated in other FIFE studies. Two examples are given that illustrate the utility of these soil moisture maps for remote sensing and hydrometeorological studies over the FIFE study area.

Outdoor propagation models with and in the absence of barriers

Analytic models for predicting the propagation of noise outdoors over uniform, flat terrain covered by a variety of ground covers have been proposed by the author and other researchers. These mathematical models are compared analytically and numerically for few ground cover impedances. Furthermore, when the terrain is partly covered by a hard pavement and partly by an absorbent ground, the models must take account of this discontinuity in the ground impedance. A review of the few analytic models developed by the author and other researchers is given and compared analytically and numerically. If a noise barrier is erected on a uniformly covered ground or over a pavement‐absorbent ground, then the barrier performance is affected by the ground absorption. Various empirical analytic models based on geometrical acoustics and diffraction, which account for multiple diffraction by barriers located on an absorbent ground, are reviewed. [Work supported by FHWA.]

On the observation of a flare‐generated shock wave at 9.7 AU by Pioneer 10

The period March 15 to May 15, 1976, was declared in advance to be the internationally recognized Study of Travelling Interplanetary Phenomena Interval II. A variety of ground‐ and space‐based equipment was requested to make coordinated studies during this part of the minimum of solar cycle 20. Following an absence of solar activity for a long period, several type II radio bursts on March 20, 1976, produced by two solar flares behind the east limb heralded a series of solar, interplanetary, and terrestrial events. These solar radio astronomical observations were followed by non‐Io‐associated radio emission from Jupiter and solar wind plasma detection at Pioneer 10 at 9.7 AU of an apparent shock wave on March 30 and April 9, 1976, respectively. In view of the fact that the solar flares on March 20 were essentially at central meridian with respect to Jupiter and Pioneer 10 and also that the sun was extremely inactive prior to that date we consider the circumstantial evidence that at least one solar‐flare‐generated shock wave propagated to the position of Pioneer 10. The average velocities of this shock wave, together with the inferred type II velocity, support previous observations and theory concerning the rapid deceleration and survival of interplanetary shock waves to distances at least as large as ∼10 AU. It is therefore believed that dissipation (other than that within shocks themselves) plays an insignificant role in shock wave dynamics within the solar wind.