Active Region Research Articles

Assessing the Performance of the ADAPT and AFT Flux Transport Models Using In Situ Measurements from Multiple Satellites

The launches of Parker Solar Probe (Parker) and Solar Orbiter (SolO) are enabling a new era of solar wind studies that track the solar wind from its origin at the photosphere, through the corona, to multiple vantage points in the inner heliosphere. A key ingredient for these models is the input photospheric magnetic field map that provides the boundary condition for the coronal portion of many heliospheric models. In this paper, we perform steady-state, data-driven magnetohydrodynamic (MHD) simulations of the solar wind during Carrington rotation 2258 with the Grid GAMERA model. We use the ADAPT and AFT flux transport models and quantitatively assess how well each model matches in situ measurements from Parker, SolO, and Earth. We find that both models reproduce the magnetic field components at Parker quantitatively well. At SolO and Earth, the magnetic field is reproduced relatively well, though not as well as at Parker, and the density is reproduced extremely poorly. The velocity is overpredicted at Parker, but not at SolO or Earth, hinting that the Wang–Sheeley–Arge (WSA) relation, fine-tuned for Earth, misses the deceleration of the solar wind near the Sun. We conclude that AFT performs quantitatively similarly to ADAPT in all cases, and that both models are comparable to a purely WSA heliospheric treatment with no MHD component. Finally, we trace field lines from SolO back to an active region outflow that was observed by Hinode/EIS, and which shows evidence of elevated charge state ratios.

Peptide-based allosteric inhibitor targets TNFR1 conformationally active region and disables receptor–ligand signaling complex

Tumor necrosis factor (TNF) receptor 1 (TNFR1) plays a pivotal role in mediating TNF induced downstream signaling and regulating inflammatory response. Recent studies have suggested that TNFR1 activation involves conformational rearrangements of preligand assembled receptor dimers and targeting receptor conformational dynamics is a viable strategy to modulate TNFR1 signaling. Here, we used a combination of biophysical, biochemical, and cellular assays, as well as molecular dynamics simulation to show that an anti-inflammatory peptide (FKCRRWQWRMKK), which we termed FKC, inhibits TNFR1 activation allosterically by altering the conformational states of the receptor dimer without blocking receptor-ligand interaction or disrupting receptor dimerization. We also demonstrated the efficacy of FKC by showing that the peptide inhibits TNFR1 signaling in HEK293 cells and attenuates inflammation in mice with intraperitoneal TNF injection. Mechanistically, we found that FKC binds to TNFR1 cysteine-rich domains (CRD2/3) and perturbs the conformational dynamics required for receptor activation. Importantly, FKC increases the frequency in the opening of both CRD2/3 and CRD4 in the receptor dimer, as well as induces a conformational opening in the cytosolic regions of the receptor. This results in an inhibitory conformational state that impedes the recruitment of downstream signaling molecules. Together, these data provide evidence on the feasibility of targeting TNFR1 conformationally active region and open new avenues for receptor-specific inhibition of TNFR1 signaling.

Earthquake supercycles and fault interaction over the past 32 ka in the Lake Ebinur area, Xinjiang, China

Earthquake prediction and disaster assessment in tectonically active regions require a continuous and complete regional seismic archive, which is commonly difficult to obtain, especially for prehistoric records. Here, high-resolution analysis of the sedimentary sequence from Lake Ebinur in Xinjiang revealed a detailed history of environment evolution since 32 ka ago. Both the Cl content and ultrafine proportion revealed the changing climate: the climate was relatively dry with low lake-water volumes from 32 to 12 ka, while the climate became warmer and wetter since 12 ka. In addition, eight earthquakes were identified by comprehensive analysis of grain size and geochemical element proxies, showing more than two seismic supercycles, with gaps of ∼10.4 ka; these gaps are much larger than those inferred previously (∼4–7 ka). Notably, these seismic events exhibited a pattern of mutual transmittance between the BoA and Jinghenan faults. Such fault interaction can occur in the Lake Ebinur area because it is dominated by weak lithosphere in which strain is easily accumulated and released; the interaction can also be attributed to the unique spatial distribution and immature nature of both faults. Combined with trenching investigations, our high-resolution analysis of lacustrine sediments can reveal a complete history of tectonic activity, which can efficiently serve regional earthquake prediction and disaster assessment.

Survey of Magnetic Field Parameters Associated with Large Solar Flares

Until now, how the magnetic fields in M/X-class flaring active regions (ARs) differ from C-class flaring ARs remains unclear. Here, we calculate the key magnetic field parameters within the area of high photospheric free energy density (HED region) for 323 ARs (217 C- and 106 M/X-flaring ARs), including total photospheric free magnetic energy density E free, total unsigned magnetic flux ΦHED, mean unsigned current helicity h c , length of the polarity inversion lines L PIL with a steep horizontal magnetic gradient, etc., and compare these with flare/coronal mass ejection (CME) properties. We first show the quantitative relations among the flare intensity, the eruptive character, and ΦHED. We reveal that ΦHED is a measure for the GOES flux upper limit of the flares in a given region. For a given ΦHED, there exists the lower limit of F SXR for eruptive flares. This means that only the relatively strong flares with the large fraction of energy release compared to the total free energy are likely to generate a CME. We also find that the combinations of E free–L PIL and E free–h c present a good ability to distinguish between C-class and M/X-class flaring ARs. Using determined critical values of E free and L PIL, one predicts correctly 93 out of 106 M/X-class flaring ARs and 159 out of 217 C-class flaring ARs. The large L PIL or h c for M/X-class flaring ARs probably implies the presence of a compact current with twisted magnetic fields winding about it.

Tectonic analysis of the Mula River Basin, Kirthar fold belt, Pakistan, using hypsometric index

The Mula River Basin is in an active tectonic region of the Kirthar fold fault belt in the Western Himalayas. The presence of numerous major faults like Chaman Fault, Kirthar Frontal Fault, and Bannh Fault near the study suggests complex tectonic processes in the region. The seismic record of the study area also indicates that this area is tectonically active. This makes the study area an ideal site to measure tectonic activity through geomorphic indices like hypsometric integrals (HI). For tectonic analysis of the Mula River Basin, we divided the study area into 309 subbasins. The results obtained from the HI calculations for the subbasins led us to the classification of the study area into three classes, i.e., class 1 (0.51–0.78), class 2 (0.37–0.50), and class 3 ([Formula: see text]), where class 1 is for the highest tectonic activity, class 2 responds to moderate, and class 3 is for the lowest tectonic activity. We calculated the hypsometric curves to understand the geomorphological cycle of the Mula River Basin. We quantified the subbasins of the Mula River Basin inside the highly active tectonic zone of Kirthar fold and fault zone as per their tectonic activity and found that a major portion of the study area indicates low tectonic activity (44.33%), medium tectonically active, and high tectonically active subbasins are 37.86% and 17.79%, respectively. These findings are supported by the presence of high-relief areas and known faults in the study area.

RESILIENCE AND VULNERABILITY: THE HAOUZ EARTHQUAKE'S EFFECT ON HOUSING IN THE WESTERN HIGH ATLAS OF MOROCCO

This article delves into the vulnerability of traditional dwellings and cluster housing in the Western High Atlas region of Morocco, highlighting the major challenges they face during earthquakes. These houses, often built with natural materials such as earth, stone and wood, reveal structural limitations in the face of nature's relentless forces. More specifically, the article looks at the devastating Al Haouz earthquake of 2023, which marked the region's history as the most powerful earthquake in over a century. It left behind a tragic legacy of loss of life and considerable material damage. This underlines the imperative of understanding the seismic risks to which these traditional dwellings are exposed, particularly in a culturally and geologically rich and tectonically active region. The article goes beyond simply identifying the problems, highlighting the considerable efforts made by the government and civil society to rebuild and prepare the region for similar disasters in the future. It also highlights the need to strengthen the resilience of these traditional dwellings and to reconsider building standards to better cope with seismic risks.

Using Moment Tensor Inversions for Rapid Seismic Source Detection and Characterization: Application to the North Korean Nuclear Tests

AbstractThe rapid detection and source characterization of any type of seismic events including earthquakes and nuclear explosions is one of the missions of many seismological laboratories. Most often, the techniques used are based on phase picking and amplitude measurements for detecting and locating events, and for estimating magnitudes. From these parameters, especially for anthropogenic sources, event screening is then done empirically, and this may lead to misinterpretations of the source nature. However, it is known that seismic waveform inversion for the determination of the moment tensor has proven to be a reliable source physics-based method for event characterization. Here, we present a technique already used for earthquake monitoring in tectonically active regions, and we test it on very shallow natural and anthropogenic events recorded in the vicinity of the Democratic People’s Republic of Korea (DPRK). From a grid of potential locations and by scanning continuous seismic waveforms, it is possible to implement a rapid detector of seismic events providing the full information of the sources (origin time, location, magnitude, mechanism, and source decomposition). We show its overall performances on all past DPRK nuclear tests and regional earthquakes. From such an approach fast complete event screening is achieved. Source uncertainties can also be estimated. This stand-alone detector and identifier of seismic events may help monitoring seismological agencies to provide a rapid and complete alert for any events within a region of interest before more in-depth discrimination analysis can be run.

Influence of an Overshoot Layer on the Morphological, Structural, Strain, and Transport Properties of InAs Quantum Wells.

InAs quantum wells (QWs) are promising material systems due to their small effective mass, narrow bandgap, strong spin-orbit coupling, large g-factor, and transparent interface to superconductors. Therefore, they are promising candidates for the implementation of topological superconducting states. Despite this potential, the growth of InAs QWs with high crystal quality and well-controlled morphology remains challenging. Adding an overshoot layer at the end of the metamorphic buffer layer, i.e., a layer with a slightly larger lattice constant than the active region of the device, helps to overcome the residual strain and provides optimally relaxed lattice parameters for the QW. In this work, we systematically investigated the influence of overshoot layer thickness on the morphological, structural, strain, and transport properties of undoped InAs QWs on GaAs(100) substrates. Transmission electron microscopy reveals that the metamorphic buffer layer, which includes the overshoot layer, provides a misfit dislocation-free InAs QW active region. Moreover, the residual strain in the active region is compressive in the sample with a 200 nm-thick overshoot layer but tensile in samples with an overshoot layer thicker than 200 nm, and it saturates to a constant value for overshoot layer thicknesses above 350 nm. We found that electron mobility does not depend on the crystallographic directions. A maximum electron mobility of 6.07 × 105 cm2/Vs at 2.6 K with a carrier concentration of 2.31 × 1011 cm-2 in the sample with a 400 nm-thick overshoot layer has been obtained.

High efficient net gain and low noise figure based vertical cavity semiconductor optical amplifiers for wavelength division multiplexing applications

Abstract This paper has demonstrated the high efficient net gain and low noise figure based vertical cavity semiconductor light amplifiers for wavelength division multiplexing applications. Previous study on the chip reflective gain variations versus SOA current under temperature effects is clarified. We have transferred light semiconductor amplifiers for wavelength multiplexing schemes applications. Amplifier output power is demonstrated with bias current and amplifier active layer region length variations based input signal power of 3, 6.5, 10 dBm, 1550 nm wavelength and optimum amplifier confinement factor of 0.45. The amplifier output noise variations are clarified against the bias current and amplifier active layer region width variations based input signal power of 3, 6.5, 10 dBm, 1550 nm wavelength and optimum amplifier confinement factor of 0.45. The output OSNR variations are studied clearly and deeply against the bias current and amplifier active layer region length variations based input signal power of 3, 6.5, 10 dBm, 1550 nm wavelength and optimum amplifier confinement factor of 0.45. The signal loss is demonstrated versus both active layer width/length and temperature based optimum 30 % gallium core dopant ratio and 28 % arsenide cladding dopant ratio at optimum input signal power of 10 dBm, 1550 nm wavelength and optimum amplifier confinement factor of 0.45. SOA amplifier output power can be enhance with the management of both bias current and input signal power and the reduction of active amplifier length. The amplifier output noise can be enhance with the management of both bias current and input signal power and the reduction of active amplifier width. Output OSNR system can be improved with the management of both bias current and input signal power and the reduction of active amplifier length. The SOA amplifier gain can be improved with the management of both bias current and input signal power and the reduction of active amplifier length. The SOA amplifier noise figure can be improved with the management of both bias current and input signal power and the reduction of active amplifier width. The signal loss can be controlled and managed by adjusting optimum 30 % gallium core dopant ratio and 28 % arsenide cladding dopant ratio, optimum active layer/with and the presence of room temperature.

Effects of three-dimensional type flow fields on mass transfer and performance of proton exchange membrane fuel cell

Developing state-of-the-art bipolar plate structures, to optimize fluid distribution, is essential to achieve better cell performance. In this paper, a three-dimensional model of PEMFC is developed and two cathode-side flow field structures are designed: two-dimensional and three-dimensional types. The two-dimensional type is the traditional “bipolar plate + gas diffusion layer” flow field structure, easily resulting in uneven distribution of reactant gas and other problems. This study describes three novel three-dimensional type flow fields (metal foam, fine-mesh, and wire-mesh). Through comprehensive performance analysis using numerical simulations, it is found that the three-dimensional type flow fields significantly improve mass transfer and output performance compared to two-dimensional type flow fields. The proposed three-dimensional type flow fields create forced convective fluid flow. It further enhances the diffusion dispersion of reactant gas, thus making fuller use of the active region. Among them, the wire-mesh flow field shows the best performance in terms of oxygen distribution, water distribution and electrical properties. The net output power density produced is 0.75068 W cm−2, higher than parallel flow field by 32.78%.

On the stability of the lithospheric geoelectrical structure resolution in Tarim – Tien Shan junction zone: application of various approaches to the magnetotelluric data inversion

For several decades, the intracontinental Tien Shan orogeny has served as a testing polygon for the study of modern geodynamic and seismic processes, carried out by Russian and foreign scientists at the Research Station RAS (Bishkek). The investigations have big practical significance for developing seismic hazzard zoning strategies. Magnetotelluric sounding, providing unique information on the lithosphere structures and rheology, plays an important role in the complex of applied geological and geophysical methods.
 The article describes the experience of studying the deep geoelectric structure of one of the most seismically active regions of the Tien Shan, the junction zone of the orogen and the Tarim plate. This experience was obtained during the interpretation of materials from the regional profile of MT soundings that cross this zone. Comparing the results of applying three different approaches to the inversion of magnetotelluric data, which differ not only in software implementations and algorithmic foundations, but also in model dimension, allows us to assess the reliability of the allocation and revealed properties of the main structural elements in the deep conductivity section, which help to clarify the seismotectonic pattern of the studied crustal zone.
 The objectives of the article also included support for new SinoProbe MT experiments.

What's in the Sound? Common and Language‐Specific Patterns in Brain Activation and Functional Connectivity for Phonological Awareness in Spanish–English Bilinguals

AbstractPhonological awareness is the stepping‐stone to learning to read as it helps children map language sounds onto letters. Theories of bilingualism posit that phonological awareness is a language‐common literacy skill. However, bilingual learners are also thought to build language‐specific representations. To illuminate common and specific dual‐language processes, we asked bilingual Spanish–English heritage language speakers (N = 60, Mage = 8.2) to complete a phonological sound‐matching task in Spanish and English during functional Near Infrared Neuroimaging (fNIRS). The left perisylvian activation was common across bilinguals' two languages, including similar active regions and functional connections. The findings further revealed language‐specific modulation of the system with more robust engagement of the temporal networks for Spanish and frontal networks for English. We interpret the results in the context of analytically demanding reading experiences in English and more informal home‐based Spanish language experiences typical of heritage language speakers.

SIMULATION OF DYNAMIC PROCESSES IN A p - i - n DIODE BY THE METHODS OF PERTURBATION THEORY

In the paper a mathematical model of the dynamic process of the electron-hole plasma formation in the active region ( i - region) of a semiconductor p - i - n - diode in the direct bias mode with a harmonic signal fed on the diode is developed. The basis of the model is a nonlinear nonstationary sin- gularly perturbed boundary value problem for a system of continuity equations of electron-hole currents and Poisson's equation. The algorithm for searching the charge carrier concentration distributions and the potential distribution is based on the asymptotic method of boundary functions and the Fourier method. In the course of the research, a technique for decomposing a nonlinear problem based on the development of perturbation theory me- thods was proposed. The initial nonlinear problem is reduced to a recurrent sequence of linear stationary boundary value problems, solved by classical and partially original analytical-numerical methods. The identification of the boundary functions in the solution of the problem provides, in particular, in contrast to the classical approximation of ambipolar diffusion, an adequate description of the electric field strength behavior in the active region of p - i - n - diodes. The obtained research results shed light on the peculiarities of the formation of the impedance characteristics of p - i - n - structures. The results of the work reveal more deeply the nature of the physical processes in the studied technical system and are aimed at improving the methodology for modeling and designing control semiconductor devices.

Phase “Rise” of The 11-Year Solar Cycle with Contribution to Global Warming – Examples from The Bulgarian Meteo Stations’ Temperature Data

A high negative correlation between the average Sun Spot Number in phase “rise” in the 11-year cycle of solar activity and the annual average Earth’s surface temperature was observed in the data from several meteorological stations – first in the temperature data from meteorological stations in Bulgaria, and then from many stations from Europe and the world. As solar activity has decreased over the last 70 years – the last few solar cycles up to the 24th number have had a monotonically decreasing number of sunspots – their negative correlation with temperature results in a rising surface air temperature. This increase is related to processes in the Sun’s magnetosphere and has nothing to do with the increasing concentration of greenhouse gases in the surface atmosphere. The increasing concentration of greenhouse gases may be also a consequence of the processes taking place on the earth’s surface as a result of solar activity and is not a cause of the increasing temperature of the earth’s surface.

Seismic performance of shared suction caisson anchors installed in liquefiable sand for floating offshore wind turbines

Shared anchors will reduce the levelized cost of energy for floating offshore wind (FOW) arrays currently under active development in various seismically active regions. This study investigates the seismic performance of a shared suction caisson anchor installed in liquefiable sand for a FOW array using a nonlinear dynamic 3D finite element analysis. The advanced UBC3D-PLM constitutive model was calibrated against cyclic element tests then validated with centrifuge experimental data. Strong ground motions with orthogonal horizontal and vertical components were applied to the model with varying frequency content, peak ground acceleration (PGA), and orientation. The model captured the stress–strain response of the soil and evolution of excess pore pressure to the onset of liquefaction, which occurred after application of a PGA of 0.2 g and above. Despite significant liquefaction caused by a PGA of 0.8 g, displacement of the anchor remained within around 10% of anchor diameter. The results suggest some resilience to pull-out during seismic loading in liquefiable soils, even with vertical tensile loading on the anchor developed by the inverse catenary. Further investigation could be carried out under specific site conditions and serviceability criteria to optimize the size of the caisson and reduce costs while ensuring anchor performance during seismic loading.

Development of analytic gradients for the Huzinaga quantum embedding method and its applications to large-scale hybrid and double hybrid DFT forces.

The theory of analytic gradients is presented for the projector-based density functional theory (DFT) embedding approach utilizing the Huzinaga-equation. The advantages of the Huzinaga-equation-based formulation are demonstrated. In particular, it is shown that the projector employed does not appear in the Lagrangian, and the potential risk of numerical problems is avoided at the evaluation of the gradients. The efficient implementation of the analytic gradient theory is presented for approaches where hybrid DFT, second-order Møller-Plesset perturbation theory, or double hybrid DFT are embedded in lower-level DFT environments. To demonstrate the applicability of the method and to gain insight into its accuracy, it is applied to equilibrium geometry optimizations, transition state searches, and potential energy surface scans. Our results show that bond lengths and angles converge rapidly with the size of the embedded system. While providing structural parameters close to high-level quality for the embedded atoms, the embedding approach has the potential to relax the coordinates of the environment as well. Our demonstrations on a 171-atom zeolite and a 570-atom protein system show that the Huzinaga-equation-based embedding can accelerate (double) hybrid gradient computations by an order of magnitude with sufficient active regions and enables affordable force evaluations or geometry optimizations for molecules of hundreds of atoms.

Gain Characteristics of Optically Pumped UVC Lasers with Wide AlGaN Single‐Quantum‐Well Active Regions

Herein, the lasing threshold and gain characteristics of ultraviolet‐C optically pumped edge‐emitting lasers with thick single‐quantum‐well (SQW) active regions are investigated by the variable‐stripe length method. Positive net modal gain is observed in lasers with AlGaN‐based SQWs with thicknesses up to 12 nm. The lasers show a reduction of the threshold power density with increasing SQW thickness, with the lowest threshold of 1.3 MW cm−2 achieved for a 9 nm SQW laser. The high gain and low threshold in lasers with thick quantum wells are attributed to lasing from excited states, where the polarization fields are screened by the carriers in the fundamental state and the barriers, thus recovering larger electron and hole wavefunctions overlap. These findings are supported by k · p simulations, and for a 9 nm SQW, the calculation predicts a contribution of the fundamental transition to the gain of 75% for non‐resonant optical excitation and below 1% for resonant optical or electrical excitation.

Limited Evidence of Late Quaternary Tectonic Surface Deformation in the Eastern Tennessee Seismic Zone, United States

ABSTRACT The ∼300-km-long eastern Tennessee seismic zone, United States, is the secondmost seismically active region east of the Rocky Mountains. Seismicity generally occurs below the Paleozoic fold-and-thrust belt within the Mesoproterozoic basement, at depths of 5–26 km, and earthquake magnitudes during the instrumental record have been moment magnitude (Mw) ≤4.8. Evidence of surface deformation may not exist or be difficult to detect because of the vegetated and soil-mantled landscape, landslides, locally steep topography, anthropogenic landscape modification, or long, irregular recurrence intervals between surface-rupturing earthquakes. Despite the deep seismicity, analog models indicate that accumulation of strike-slip or oblique-slip displacement at depth could be expected to propagate upward through the Paleozoic section, producing a detectable surficial signal of distributed faulting. To identify potential surface deformation, we interrogated the landscape at different spatial scales. We evaluated morphotectonic and channel metrics, such as channel sinuosity and catchment-scale hypsometry. In addition, we mapped possible fault-related topographic features on 1-m lidar data. Finally, we integrated our observations with available bedrock and Quaternary surficial mapping and subsurface geophysical data. At a regional scale, most morphotectonic and channel metrics have a strong lithologic control. Within smaller regions of similar lithology, we observe changes in landscape metrics like channel sinuosity and catchment-scale hypsometry that spatially correlate with new lineaments identified in this study and previously mapped east–west Cenozoic faults. These faults have apparent left-lateral offsets, are optimally oriented to slip in the current stress field, and match kinematics from the recent focal mechanisms, but do not clearly preserve evidence of late Pleistocene or Holocene tectonic surface deformation. Most newly mapped lineaments might be explained by either tectonic or nontectonic origins, such as fluvial or karst processes. We also reevaluated a previously described paleoseismic site and interpret that the exposure does not record evidence of late Pleistocene faulting but instead is explained by fluvial stratigraphy.

DEM analysis of flow dynamics of cohesive particles in a rotating drum

Cohesive particles, prevalent in chemical and metallurgical industries, necessitate a comprehensive investigation of their behavior. This study employs the discrete element method to predict the motion of two distinct types of cohesive particles within a three-dimensional rotating drum, with the evaluation of the influence of rotational speed on particle-level parameters, encompassing velocities, angular velocities, dispersion coefficients, and contact forces. The findings reveal that wet particles treated with a honey-additive exhibit heightened inter-particle bonding, resulting in flatter surfaces on inclined planes. Cohesive particles within the active region attain greater translational velocities than their counterparts within the passive region. The x-direction dispersion intensity of water-additive particles in both the active and passive regions increases from 2.41 × 10−4 m2/s and 9.99 × 10−5 m2/s to 5.75 × 10−4 m2/s and 3.34 × 10−4 m2/s, respectively, with the increase in rotational speed from 5.6 RPM to 11.6 RPM. Particles with a honey-additive demonstrate larger dispersion coefficients along the x- and y-axes, as well as higher velocities and contact forces, albeit lower angular velocities in contrast to particles treated with a water-additive. Furthermore, an escalation in rotational speed amplifies the dispersion coefficients and contact forces of the cohesive particles. The rotating kinetic energy of the particles with water-additive and honey-additive increases from 0.005 J and 0.01 J to 0.01 J and 0.045 J, respectively.

Double-decker Pair of Flux Ropes Formed by Two Successive Tether-cutting Eruptions

Double-decker filaments and their eruptions have been widely observed in recent years, but their physical formation mechanism is still unclear. Using high spatiotemporal resolution, multi-wavelength observations taken by the New Vacuum Solar Telescope and the Solar Dynamics Observatory, we show the formation of a double-decker pair of flux rope system by two successive tether-cutting eruptions in a bipolar active region. Due to the combined effect of photospheric shearing and convergence motions around the active region’s polarity inversion line (PIL), the arms of two overlapping inverse-S-shaped short filaments reconnected at their intersection, which created a simultaneous upward-moving magnetic flux rope (MFR) and a downward-moving post-flare-loop (PFL) system striding the PIL. Meanwhile, four bright flare ribbons appeared at the footpoints of the newly formed MFR and the PFL. As the MFR rose, two elongated flare ribbons connected by a relatively larger PFL appeared on either side of the PIL. After a few minutes, another MFR formed in the same way at the same location and then erupted in the same direction as the first one. Detailed observational results suggest that the eruption of the first MFR might experienced a short pause before its successful eruption, while the second MFR was a failed eruption. This implies that the two newly formed MFRs might reach a new equilibrium at relatively higher heights for a while, which can be regarded as a transient double-decker flux rope system. The observations can well be explained by the tether-cutting model, and we propose that two successive confined tether-cutting eruptions can naturally produce a double-decker flux rope system, especially when the background coronal magnetic field has a saddle-like distribution of magnetic decay index profile in height.