Transient Variations Research Articles

Elasto-visco-plastic flows in benchmark geometries: I. 4 to 1 planar contraction

We present predictions for the flow of elastoviscoplastic (EVP) fluids in the 4 to 1 planar contraction geometry. The Saramito-Herschel-Bulkley fluid model is solved via the finite-volume method with the OpenFOAM software. Both the constitutive model and the solution method require using transient simulations. In this benchmark geometry, whereas viscoelastic fluids may exhibit two vortices, referred to as lip and corner vortices, we find that EVP materials are unyielded in the concave corners. They are also unyielded along the mid-plane of both channels, but not around the contraction area where all stress components are larger. The unyielded areas using this EVP model are qualitatively similar to those using the standard viscoplastic models, when the Bingham or the Weissenberg numbers are lower than critical values, and then, a steady state is reached. When these two dimensionless numbers increase while they remain below the respective critical values, which are interdependent, (a) the unyielded regions expand and shift in the flow direction, and (b) the maximum velocity increases at the entrance of the contraction. Increasing material elasticity collaborates with increasing the yield stress, which expands the unyielded areas, because it deforms the material more prior to yielding compared to stiffer materials. Above the critical Weissenberg number, transient variations appear for longer times in all variables, including the yield surface, instead of a monotonic approach to the steady state. They may lead to oscillations which are damped or of constant amplitude or approach a flow with rather smooth path lines but complex stress field without a plane of symmetry, under creeping conditions. These patterns arise near the entrance of the narrow channel, where the curvature of the path lines is highest and its coupling with the increased elasticity triggers a purely elastic instability. Similarly, a critical value of the yield stress exists above which such phenomena are predicted.

Novel DC-link voltage regulation and seamless transfer control strategy of a battery-based microgrid system

The main challenge of modern microgrids (MGs) is the capability to operate in either grid-connected mode (GC) or islanding (IS) mode with DC-link voltage regulation for all the utilized parallel-connected DC-AC converters in the MG during all operating modes and, at the same time, is capable of transferring seamlessly between these two operating modes. This paper suggests a novel control strategy capable of operating a battery-based MG system in each of the GC and the IS modes and, at the same time, seamlessly transferring it between these two operating modes. A PQ controller is utilized to realize the GC operation, whereas a V/f controller is used for the IS operation. The smooth transfer between the two modes is accomplished by minimizing the transient variations in the MG voltage, current, frequency and phase at the point of common coupling (PCC). Additionally, the suggested strategy is qualified to deliver a novel regulation and a transient-free transition for the DC-link voltage of the used bi-directional DC-AC converter of the considered battery-based MG system. Therefore, the suggested control strategy can potentially improve the reliability of the considered battery-based MG system. The considered battery-based MG system is simulated and controlled by utilizing MATLAB/Simulink. The simulation results demonstrate that the suggested control strategy can effectively act during the operation of the considered battery-based MG system, either in the GC mode or the IS mode, and it can also effectively control the transitions between the two operating modes.

Time-dependent model of temperature distribution in continuous flow pulsed electric field treatment chambers

A key component of a continuous flow pulsed electric field (PEF) system is the treatment chamber, where the product is exposed to electric pulses. Determination of the temperature distribution in the chamber during PEF treatment is important since high local increases in temperatures can affect the quality of the product. Coupled simulations of electric field, fluid flow, and heating in the existing literature do not model each individual electric pulse, but rather employ a “duty cycle” approach, which does not account for transient variations in treatment intensity and temperature changes in the medium. We present a time-dependent approach to modelling PEF treatment in continuous flow treatment chambers, which can model each pulse separately, and thus enables a more accurate study of temporal and spatial distributions of electric field and temperature. The model has been validated on laboratory scale treatment chambers of parallel plate or colinear design and using realistic protocols. Industrial relevance textThe paper is relevant to all pulsed electric field (PEF) applications either on laboratory or industrial scale that implement a continuous flow treatment chamber. It presents an improved modelling approach which allows for an analysis of the electrical current, electric field, and temperature distribution in the chamber during, at the end, and in between application of electrical pulses. The model can be used to predict the peak temperature at the end of each pulse in the hot spots, which if large enough could potentially lead to thermal damage of the product or in extreme cases even potential local boiling of the medium, resulting not only in degradation of the treated product, but also in accelerated electrode fouling, oxidation, and dissolution (etching), as well as arcing. This would not only affect the quality of the treated product but would also affect the wear and lifetime of electrodes/chambers, and of the pulse generator. The model can also be used to avoid expensive trial-and-error optimization of the PEF protocols and chamber geometries in situ.

Ultrafast, self-powered monolithic pressure sensing technology induced by piezo-pyrophototronics

Pressure sensing is a pivotal aspect of modern technology that has been extensively explored, but still presents significant challenges. This work introduces an innovative ultrafast self-powered pressure sensing technology by harnessing the lateral photovoltaic effect (LPE) in a CIGS heterojunction via piezo-pyrophototronics. By utilizing non-uniform irradiation, a surface gradient of charge carriers is induced, resulting in the generation of a lateral photovoltage (LPV) that contributes to the excellent self-powered characteristic of the sensor. This gradient is then coupled with external pressure through the piezo-phototronic effect, enabling the sensing capability of the device. The enhancement of LPV, which is dependent on the irradiation position, power and wavelength, exhibits an extremely linear relationship with the applied external pressure ranging from 0 to 2.0 MPa. Besides, the pyroelectric field generated by transient temperature variations introduces an additional modulation to the pressure sensing effect, leading to an impressive pressure sensitivity of 64.25 mV/MPa, and a rapid response speed of 7.8/8.9 μs. This work highlights the benefits of the lateral photovoltaic effect, piezo-phototronic effect, and pyroelectric modulation in developing highly sensitive and ultrafast self-powered pressure sensors.

Sewage sludge amendment of rice as a potential alternative to mineral fertilizer: Analyses of physiological, biochemical and molecular mechanisms of plant response

Sewage sludge (SS) disposal poses environmental concerns, yet its organic matter, macro- and micronutrients, make it potentially beneficial for enhancing soil quality and crop yield. This study focuses on three types of SS: “R10” (SS1), which is commonly used in agricultural practices, and two environmentally friendlier options (SS2 and SS3), as alternatives to mineral fertilizer (urea) for rice cultivation. A pot experiment was conducted to investigate the ecophysiological, biochemical, and molecular responses of rice at three different growth stages. SS application led to a significant increase in biomass production (particularly SS3), along with increased nitrogen (N) levels. Enhanced chlorophyll content was observed in SS-treated plants, especially during inflorescence emergence (with the highest content in SS3 plants). At the ecophysiological and biochemical levels, SS treatments did not adversely affect plant health, as evidenced by unchanged values of maximal PSII photochemical efficiency and malondialdehyde by-products. At biochemical and gene expression levels, antioxidant enzyme activities showed transient variations, likely related to physiological adjustments rather than oxidative stress. Ascorbic acid and glutathione did not significantly vary. This study concludes that the use of SS in soil can be a viable alternative fertilizer for rice plants, with positive effects on biomass, chlorophyll content, and no adverse effects on plant health. Among the tested SSs, SS3 showed the most positive effect, even compared to commercial fertilizer. These results suggest that SS application could improve rice yield while addressing environmental concerns surrounding SS disposal.

Developing a validated simulation model of micro-zonal air-conditioning to evaluate thermal comfort parameters

ABSTRACT Micro-Zonal Occupant-Centric Control (MZOCC) helps in reducing building energy consumption by conditioning only the occupied regions in a room. For this, MZOCC divides a large room such as open-plan offices into virtual micro-zones to allow independent diffuser level control. But, unplanned MZOCC can lead to heavy thermal gradients and deflection of air jets, leading to thermal discomfort. To evaluate thermal comfort at different regions of a room under MZOCC, there is a need to accurately model parameters of thermal comfort. Field studies, exploring the transient variations in air temperature, humidity and velocity at different regions of the room due to MZOCC, are limited. At the same time, developing validated simulation models or digital twins using experimental data helps in exploring micro-zonal strategies to arrive at the best strategy. The aim of this study is to create a digital twin of an open-plan office and model the parameters required to estimate thermal comfort. This study senses transient variations in air temperature, velocity and humidity using a wireless sensor network and develops a computational fluid dynamic (CFD) model that can accurately model the sensed transient variations. Field data, constituting external surface temperatures captured using thermal images, variations in air-conditioning control strategy, dynamic occupancy and location, are periodically updated in the digital twin. The CFD model accurately predicts the trends in variations in indoor temperature, velocity and humidity at different regions of the room. The developed digital twin can be used in future studies to evaluate thermal comfort and plan MZOCC control strategies.

Study on transient thermal state of steel piston in diesel engine under cold start condition

The thermal load issue of pistons remains a topic of active research, especially the transient thermal state of steel pistons in diesel engines under cold start conditions has not been studied in depth. In this paper, a new steel piston power assembly was designed and developed on the basis of a small-bore diesel engine. A real-time temperature test system for the steel piston temperature field was developed to address the problem of the inability to obtain real-time temperature data. The test system was applied to the steel piston to investigate the transient variations in temperature field, thermal stress, and thermal deformation at different starting temperatures. The results show that the temperature field of steel pistons exhibits exponential growth in the early stage of cold start and then tends to stabilize after about 44 s. The lower the cold start temperature and the closer the monitoring points are to the high-temperature combustion gas, the faster the rate of temperature rise. The thermal stress of the steel piston initially increases rapidly, then decreases, and subsequently increases again until reaching a stable level. The lower the starting temperature, the longer the thermal stress inflection point of the monitoring point will be. The variation of thermal deformation of the steel piston follows the same trend as that of the temperature field.

A comprehensive prediction model of drilling wellbore temperature variation mechanism under deepwater high temperature and high pressure

Comprehensively considering the impact of properties of drilling fluid at high temperature and high pressure (HTHP), drill string eccentricity, rotation, and rock breaking of drill bit on the annular temperature profile, transient temperature variations were predicted by using a wellbore heat transfer model. The model was numerically solved using the finite difference method. Compared to DRILLBENCH simulations, the predicted model was more consistent with the field-measured data. The calculations revealed that comprehensively considering various heat source factors made the annular temperature closer to the actual wellbore value, with a temperature difference of up to 10.66 °C. When considering variations of properties of drilling fluid at HTHP, the lower section of the annulus showed a significant decrease in temperature with depth, with a bottom-hole temperature difference of 5.4 °C. The bottom-hole temperature decreased by about 2.6 °C from concentric to eccentric drill string, and the pressure difference was about 1 MPa. Compared to drill string eccentricity, rotation and rock breaking of drill bit had a greater impact on annular temperature, with bottom-hole temperature differences of 13 °C and 22 °C, respectively. Accurate temperature modeling can better understand and predict the variation patterns of wellbore temperature, providing important guidance for the development of deepwater drilling.

Multiphysics modeling and experimental validation of heat and mass transfer for the vacuum induction melting process

Vacuum induction melting is crucial in casting nickel-based superalloy components, ensuring excellent properties for aero-engine applications. Precise melting temperatures are vital for achieving optimal metallurgical quality before casting. Hence, a multiphysics numerical model is developed to simulate the induction melting process for the Inconel 718 superalloy. The proposed holistic model integrates magnetic fields, induced currents, and heat and momentum transfer phenomena in a single coupled model. A moving mesh approach reproduces the magneto-hydrodynamic behavior of the free surface, simulating the oscillations of the melt. The stabilized deformed surface profile is correlated with experimental measurements, reporting a proper correlation. Then, the flow field and recirculation effect are modeled with a Low Reynolds Number turbulence approach and coupled with the melt convective heat transfer, developing a complete magneto-thermo-hydrodynamic model. In a laboratory-scale vacuum induction melting furnace, transient melting operation variables are characterized and introduced to the numerical model to compute the temperature evolution. An accurate reproduction of the transient melt temperature variations is reported with a relative error of less than 5%. The influence of the crucible thermal insulating capacity is assessed, emissivity dependence evaluated, and melt homogenization is reported at different process stages. This comprehensive numerical and experimental approach offers valuable insights for enhancing vacuum induction melting for Ni-based superalloys.

Investigating hybrid nanoparticles for drug delivery in multi-stenosed catheterized arteries under magnetic field effects

This groundbreaking study pioneers the exploration of the therapeutic implications of a constant magnetic field simultaneously with hybrid nanoparticles on blood flow within a tapered artery, characterized by multiple stenosis along its exterior walls and a central thrombus, employing three-dimensional bio-fluid simulations. In addition, a magnetized catheter is inserted into the thrombus to increase the therapeutic potential of this novel method. The flow condition under consideration has applications in targeted medication distribution, improved medical device design, and improved diagnostics, as well as in advancing healthcare and biomedical engineering. Our investigation primarily aims to optimize blood flow efficiency, encompassing key parameters like pressure, velocity, and heat fluctuations influenced by diverse geometric constraints within the stenotic artery. Precise solutions are obtained through the finite element method (FEM) coupled with advanced bio-fluid dynamics (BFD) software. Hybrid nanoparticles and magnetic fields impacted pressure and velocity, notably reducing pressure within the stenosis. Convective heat flux remained uniform, while temperature profiles showed consistent inlet rise and gradual decline with transient variations. This approach promotes fluid flow, and convection within stenosed arteries, enhances heat transport, evacuates heat from stenotic regions, and improves heat dispersion to surrounding tissues. These findings hold promise for targeted therapies, benefiting patients with vascular disorders, and advancing our understanding of complex bio-fluid dynamics.

Transient Greenland Ice-Sheet Mass Variations From Multiple Geodetic Data Over the Last Two Decades

Transient Greenland Ice-Sheet Mass Variations From Multiple Geodetic Data Over the Last Two Decades

Propulsive characteristics of single-pulsed jets with tube and orifice openings

The effects of the nozzle exit geometry on the unsteady propulsive characteristics of single-pulsed jets are studied numerically. For both tube and orifice nozzles, the jet exit configuration is parameterized by the diameter ratio RD, which is defined as the ratio of the nozzle entrance D0 to the jet exit diameters D. It is found that the diameter ratio has significant influence on the propulsive characteristics of the single-pulsed jet during its entire ejection phase. The total impulse production is augmented considerably as the diameter ratio increases until a critical value of RD_cir≈2.0 is approached. The larger impulse production by the orifice nozzles over the tube nozzle stems from the persistent over-pressure contribution at the jet exit due largely to the fact that the flow contraction near the jet exit of the orifice nozzle results in the intensification of the radial velocity gradients and higher local pressure. By using the existing prediction of the contraction coefficient Cc to account for the flow contraction, a theoretical model has been developed with the quasi-one-dimensional flow approximation to predict the pressure thrust at the jet exit during the steady discharging stage, showing good agreement with the present numerical results. Moreover, the pressure force acting on the vertical wall of the orifice nozzle, which is proportional to the wall area, is found to be primarily responsible for the larger transient variations in the jet impulse during the onset and end of the jet ejection phase as the diameter ratio increases.

Ultrafast Laser-Induced Dynamics of Non-Equilibrium Electron Spill-Out in Nanoplasmonic Bilayers.

Contemporary quantum plasmonics capture subtle corrections to the properties of plasmonic nano-objects in equilibrium. Here, we demonstrate non-equilibrium spill-out redistribution of the electronic density at the ultrafast time scale. As revealed by time-resolved 2D spectroscopy of nanoplasmonic Fe/Au bilayers, an injection of the laser-excited non-thermal electrons induces transient electron spill-out thus changing the plasma frequency. The response of the local electronic density switches the electronic density behavior from spill-in to strong (an order of magnitude larger) spill-out at the femtosecond time scale. The superdiffusive transport of hot electrons and the lack of a direct laser heating indicate significantly non-thermal origin of the underlying physics. Our results demonstrate an ultrafast and non-thermal way to control surface plasmon dispersion through transient variations of the spatial electron distribution at the nanoscale. These findings expand quantum plasmonics into previously unexplored directions by introducing ultrashort time scales in the non-equilibrium electronic systems.

Wavelet Transforms of Microlensing Data: Denoising, Extracting Intrinsic Pulsations, and Planetary Signals

Wavelets are waveform functions that describe transient and unstable variations, such as noise. In this work, we study the advantages of discrete and continuous wavelet transforms (DWTs and CWTs) of microlensing data to denoise them and extract their planetary signals and intrinsic pulsations hidden by noise. We first generate synthetic microlensing data and apply wavelet denoising to them. For these simulated microlensing data with ideally Gaussian noise based on the Optical Gravitational Lensing Experiment (OGLE) photometric accuracy, denoising with DWTs reduces standard deviations of data from real models by 0.044–0.048 mag. The efficiency to regenerate real models and planetary signals with denoised data strongly depends on the observing cadence and decreases from 37% to 0.01% with increasing cadence from 15 min to 6 hr. We then apply denoising on 100 microlensing events discovered by the OGLE group. On average, wavelet denoising for these data improves standard deviations and of data with respect to the best-fit models by 0.023 mag and 1.16, respectively. The best-performing wavelets (based on the highest signal-to-noise ratio’s peak (), the highest Pearson’s correlation, or the lowest root mean squared error for denoised data) are from the Symlet and Biorthogonal wavelet families in simulated and OGLE data, respectively. In some denoised data, intrinsic stellar pulsations or small planetary like deviations appear that were covered with noise in raw data. However, through DWT denoising rather flattened and wide planetary signals could be reconstructed rather than sharp signals. CWTs and 3D frequency–power–time maps could inform about the existence of sharp signals.

Conduit Processes at the Haukadalur Geyser‐Hosting Hydrothermal Field (Iceland) Revealed by In Situ Temperature and High‐Speed Camera Measurements

AbstractGeysers fascinate scientists and visitors for several centuries. However, many driving mechanisms such as heat transfer in the conduit and in the subsurface remain poorly understood. We document for the first time transient temperature variations inside the active Strokkur's and nearby quasi‐dormant Great Geysir's conduits, Iceland. While recording temperature inside the conduit, we visually monitored Strokkur's activity at the vent with a high‐speed camera, providing a high temporal resolution of the eruptions. Our results reveal heat transfer from a bubble trap to and through the conduit. We propose a model for the eruptive cycle of Strokkur that includes vapor slug rise, eruption, and conduit refill. Each water jet of an eruption is marked by an initial pulse of liquid water and vapor, emitted at a velocity between 5 and 28 m/s and generally followed by a second pulse less than a second later. The timing of eruptions coincides with temperature maxima in the conduit. After the eruption, the conduit is refilled by water falling back in the pool and drained from neighboring groundwater‐saturated geological units. This results in a temperature drop, the amplitude of which increases with depth while its period is reduced. This reflects faster heat transfer in the deeper than shallower part of the conduit. The amplitude of temperature drop following an eruption also increases with the eruption order, implying larger heat release by higher‐order eruptions. Temperature in the conduit subsequently increases until the next eruption, starting then a new cycle.

Meta-analysis reveals the predictable dynamic development of the gut microbiota in commercial pigs.

Understanding the mechanisms of microbiome assembly during host development is crucial for successful modulation of the gut microbiome to improve host health and growth. However, results from previous microbial intervention studies to improve swine growth have largely been inconsistent due to the constantly changing nature of the gut microbiota and limited longitudinal sampling. Detailed characterization of the swine gut microbiota through meta-analysis allows us to understand the dynamics of microbial community succession, as well as the transient and natural variations between time points and animals. A total of 3,313 fecal microbial communities from over 349 pigs covering 60 time points (from birth to market age) from 14 publications were included in this meta-analysis. Despite differences in animal breeds and management, generalizable patterns of community assembly were identified. Alpha diversity continuously increased during early stages of animal growth and more slowly in the later stages. Beta regression analysis revealed that more microbial taxa were enriched, while fewer were excluded by the gut microbiota. The microbial community structure also changed significantly between days at early ages and became more similar as pigs aged, as revealed by dissimilarity and distance metrics. Dirichlet multinomial mixtures analysis supported gradient microbial clustering in longitudinal pig fecal samples, and we found that the early samples spread to more clusters than those from older pigs. Random forest regression identified 30 operational taxonomic units as potential microbial biomarkers for modeling swine gut microbiota development. External validation showed this model could be generalized to future microbiome studies conducted in suckling and weaning pigs and adds to the toolkit to quantify community succession. IMPORTANCE The swine gut microbiome undergoes an age-dependent assembly pattern with a developmental phase at early ages and a stabilization phase at later ages. Shorter time intervals and a wider range of data sources provided a clearer understanding of the gut microbiota colonization and succession and their associations with pig growth and development. The rapidly changing microbiota of suckling and weaning pigs implies potential time targets for growth and health regulation through gut microbiota manipulation. Since swine gut microbiota development is predictable, swine microbiota age can be calculated and compared between animal treatment groups rather than relying only on static time-matched comparisons.

A central serotonin regulating gene polymorphism (TPH2) determines vulnerability to acute tryptophan depletion-induced anxiety and ventromedial prefrontal threat reactivity in healthy young men

Serotonin (5-HT) has long been implicated in adaptive emotion regulation as well as the development and treatment of emotional dysregulations in mental disorders. Accumulating evidence suggests a genetic vulnerability may render some individuals at a greater risk for the detrimental effects of transient variations in 5-HT signaling. The present study aimed to investigate whether individual variations in the Tryptophan hydroxylase 2 (TPH2) genetics influence susceptibility for behavioral and neural threat reactivity dysregulations during transiently decreased 5-HT signaling. To this end, interactive effects between TPH2 (rs4570625) genotype and acute tryptophan depletion (ATD) on threat reactivity were examined in a within-subject placebo-controlled pharmacological fMRI trial (n = 51). A priori genotype stratification of extreme groups (GG vs. TT) allowed balanced sampling. While no main effects of ATD on neural reactivity to threat-related stimuli and mood state were observed in the entire sample, accounting for TPH2 genotype revealed an ATD-induced increase in subjective anxious arousal in the GG but not the TT carriers. The effects were mirrored on the neural level, such that ATD specifically reduced ventromedial prefrontal cortex reactivity towards threat-related stimuli in the GG carriers. Furthermore, the ATD-induced increase in subjective anxiety positively associated with the extent of ATD-induced changes in ventromedial prefrontal cortex activity in response to threat-related stimuli in GG carriers. Together the present findings suggest for the first time that individual variations in TPH2 genetics render individuals susceptible to the anxiogenic and neural effects of a transient decrease in 5-HT signaling.

Laboratory Comparison of Low-Cost Particulate Matter Sensors to Measure Transient Events of Pollution-Part B-Particle Number Concentrations.

Low-cost Particulate Matter (PM) sensors offer an excellent opportunity to improve our knowledge about this type of pollution. Their size and cost, which support multi-node network deployment, along with their temporal resolution, enable them to report fine spatio-temporal resolution for a given area. These sensors have known issues across performance metrics. Generally, the literature focuses on the PM mass concentration reported by these sensors, but some models of sensors also report Particle Number Concentrations (PNCs) segregated into different PM size ranges. In this study, eight units each of Alphasense OPC-R1, Plantower PMS5003 and Sensirion SPS30 have been exposed, under controlled conditions, to short-lived peaks of PM generated using two different combustion sources of PM, exposing the sensors' to different particle size distributions to quantify and better understand the low-cost sensors performance across a range of relevant environmental ranges. The PNCs reported by the sensors were analysed to characterise sensor-reported particle size distribution, to determine whether sensor-reported PNCs can follow the transient variations of PM observed by the reference instruments and to determine the relative impact of different variables on the performances of the sensors. This study shows that the Alphasense OPC-R1 reported at least five size ranges independently from each other, that the Sensirion SPS30 reported two size ranges independently from each other and that all the size ranges reported by the Plantower PMS5003 were not independent of each other. It demonstrates that all sensors tested here could track the fine temporal variation of PNCs, that the Alphasense OPC-R1 could closely follow the variations of size distribution between the two sources of PM, and it shows that particle size distribution and composition are more impactful on sensor measurements than relative humidity.

Operating strategy investigation of a solid oxide electrolysis cell under large scale transient electrical inputs

The solid oxide electrolysis cell technology can be integrated with intermittent power sources such as wind to produce hydrogen by water electrolysis for electrical energy storage. However, the fluctuation of wind power may induce transient variations in the electrochemical and thermal performances of the solid oxide electrolysis cell. Applying active operation strategies helps improve the transient performances of the electrolysis cell under large-scale dynamic electrical inputs. In this study, a three-dimensional electrochemical-mass-heat coupling dynamic model of the solid oxide electrolysis cell with voltage-current curve and electrochemical impedance validation is developed to investigate the effects of different active operation strategies. The mechanism and feasibility of the fuel and air operation strategies in the current fluctuation are examined based on the electrochemical, concentration, and temperature responses. The optimized active fuel operating strategy is capable of achieving a dynamic range of 0–163 %. The effectiveness of the air operating strategy depends on the preheating temperature and flow rate of the air, and their selection requires a balance between temperature control ability and temperature gradient. Integrating the advantages of both fuel and air operation strategies, a fuel–air hybrid operating strategy is proposed to further increase the dynamic range to 0–170 %.

Parametrization of Energetic Ion and Electron Fluxes in the Near‐Earth Magnetotail

AbstractThe near‐Earth plasma sheet region is the main source of energetic (tens to hundreds keV) ion and electron populations transported by convection and injections into the inner magnetosphere. Energetic ions from the plasma sheet contribute to the ring current, whereas energetic electrons contribute to the radiation belt seed population for further acceleration to relativistic energies. Near‐Earth plasma sheet energetic fluxes have been traditionally used to set boundary conditions for radiation belt and ring current models. This study provides an empirical parametrization for ∼75 keV flux intensity as a function of the geomagnetic activity index auroral electrojet and the equatorial magnetic field Bz. Such parametrization includes the dynamic magnetic field configuration in the near‐Earth plasma sheet and may be merged with empirical magnetic field models. We also provide models extending this parametrization to the [20, 300] keV of electron energy range and [75, 300] keV of ion energy range. The parametrization is developed based on THEMIS and Geostationary Operational Environmental Satellite measurements, and verified by comparison with MMS measurements in the near‐Earth plasma sheet. This parametrization incorporates meso‐scale transient flux variations associated with Bz perturbations into ring current and radiation belt simulations.