Drift Paths Research Articles

The Storm‐Time Ring Current Response to ICMEs and CIRs Using Van Allen Probe Observations

AbstractUsing Van Allen Probe observations of the inner magnetosphere during geomagnetic storms driven by interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs), we characterize the impact of these drivers on the storm‐time ring current development. Using 25 ICME‐ and 35 CIR‐driven storms, we have determined the ring current pressure development during the prestorm, main, early‐recovery, and late‐recovery storm phases, as a function of magnetic local time, L shell and ion species (H+, He+, and O+) over the 100‐ to 600‐keV energy range. Consistent with previous results, we find that during the storm main phase, most of the ring current pressure in the inner magnetosphere is contributed by particles on open drift paths drifting duskward leading to a strong partial ring current. The largest difference between the ICME and CIR ring current responses during the storm main and early‐recovery phases is the difference in the response of the <~55‐keV O+ to these drivers. While the H+ pressure response shows similar source and convection patterns for ICME and CIR storms, the O+ pressure response is significantly stronger for ICME storms. The ICME O+ pressure increases more strongly than H+ with decreasing L and peaks at lower L shells than H+.

Influence of the space charge of an ion beam on the time-of-flight diagnostics of its composition

The results of time-of-flight diagnostics of the composition of high-intensity pulsed ion beams are presented. The experiments were performed on a diode of focusing and flat geometry, in the mode of self-magnetic insulation of electrons (accelerating voltage 250–300 kV, pulse duration 120 ns, ion current density 20–300 A/cm2), and a focusing diode in an external magnetic insulation mode (300 kV, 80 ns, 100–200 A/cm2). A delay in the registration of protons by 40–50 ns (on the drift path 14–16 cm) was found in the absence of a delay in the registration of heavy ions. It has been shown that this delay can be related to the deceleration of light ions during the transport from the diode to a collimated Faraday cup. This effect of spatial compression of the ion beam in the direction of the drift increases its pulse power but complicates the time-of-flight diagnostics of its composition.

A study of the radiation tolerance of poly-crystalline and single-crystalline CVD diamond to 800 MeV and 24 GeV protons

We have measured the radiation tolerance of poly-crystalline and single-crystalline diamonds grown by the chemical vapor deposition (CVD) process by measuring the charge collected before and after irradiation in a 50 m pitch strip detector fabricated on each diamond sample. We irradiated one group of sensors with 800 MeV protons, and a second group of sensors with 24 GeV protons, in steps, to protons cm−2 and protons cm−2 respectively. We observe the sum of mean drift paths for electrons and holes for both poly-crystalline CVD diamond and single-crystalline CVD diamond decreases with irradiation fluence from its initial value according to a simple damage curve characterized by a damage constant for each irradiation energy and the irradiation fluence. We find for each irradiation energy the damage constant, for poly-crystalline CVD diamond to be the same within statistical errors as the damage constant for single-crystalline CVD diamond. We find the damage constant for diamond irradiated with 24 GeV protons to be and the damage constant for diamond irradiated with 800 MeV protons to be . Moreover, we observe the pulse height decreases with fluence for poly-crystalline CVD material and within statistical errors does not change with fluence for single-crystalline CVD material for both 24 GeV proton irradiation and 800 MeV proton irradiation. Finally, we have measured the uniformity of each sample as a function of fluence and observed that for poly-crystalline CVD diamond the samples become more uniform with fluence while for single-crystalline CVD diamond the uniformity does not change with fluence.

The Storm Time Development of Source Electrons and Chorus Wave Activity During CME‐ and CIR‐Driven Storms

AbstractWhistler mode chorus waves influence the dynamics of the Earth's radiation belts and the inner magnetosphere through gyroresonant wave particle interactions. Chorus waves are generated by anisotropic hot electrons from a few to tens of keV, called source electrons, which have increased access from the nightside plasma sheet to the inner magnetosphere during geomagnetic storms. The primary drivers of geomagnetic storms are coronal mass ejections (CMEs) and corotating interaction regions (CIRs). Through differences in their characteristic physical parameters, they can each impact the nightside plasma sheet differently. Using Van Allen Probes observations, we have conducted a superposed epoch analysis of chorus wave activity and source electron development across all local times between L = 2–6 during 25 CME‐ and 35 CIR‐driven storms. The superposed epoch analysis shows that chorus wave power follows the storm phase‐dependent access of the source electron population. Chorus waves and source electrons are observed on the dawnside during the main phase, when open drift path access via eastward convective drift from the plasma sheet is enhanced. During the recovery phase, chorus waves and source electrons are observed at all magnetic local times with low intensities, exemplifying the formation of a weak symmetric, trapped electron population. A linear theory approximation for wave growth from source electron observations shows that increased wave growth follows the enhanced source electrons during each storm phase. CME and CIR storms display similar behavior and levels of average wave power; however, chorus wave activity reaches lower L‐shells during CME storms on average.

A particle detector that exploits Liquid Argon scintillation light

A number of innovative experiments dedicated to neutrino oscillations and rare event physics, such as direct searches for dark matter particles or neutrinoless double beta decays, are using liquefied noble-gases, particularly Liquid Argon (LAr), as detection media. Among many advantages of noble liquids, from the detection point of view, the most important ones are high scintillation and ionisation yields, possible long drift paths of ionisation electrons and feasible large detector masses. LAr is sufficiently dense and relatively cheap and therefore is the only adequate noble liquid for huge volumes.This paper describes a particle detection system that exploits the prompt signals from the scintillation light produced by ionising particles in LAr. The detector has been exposed to cosmic rays. The system performance in terms of trigger efficiency and timing resolution, with a view to its application in neutrino detectors, is presented.

The Effects of Localized Thermal Pressure on Equilibrium Magnetic Fields and Particle Drifts in The Inner Magnetosphere

AbstractLocalized injections of hot anisotropic plasma sheet particles into the inner magnetosphere can significantly deform the quiet time dipole‐like magnetic field and thus disturb electron and ion's drift paths and scattering rates. Although many details of magnetic field deformation can be inferred from empirical models, roles of different characteristics of injected plasma on the structure of such deformation require further investigation. In this study, we use the 2‐D axisymmetric equilibrium model to calculate self‐consistent magnetic field in force balance with a Gaussian thermal pressure distribution characterized by four input parameters: the ratio between plasma pressure and magnetic pressure (β) at the pressure peak β0, the radial location of the pressure peak L0, the width of the half peak pressure σ0, and the equatorial pressure anisotropy Ae. Using the modeled magnetic field, we find that the magnetic field perturbation increases with increasing β0 and decreasing σ0 while the magnetic curvature perturbation increases with increasing Ae, β0, and σ0 and decreasing L0. For energetic particles the change of magnetic gradient drift motion is much greater than that of curvature drift motion. The magnetic dip structure formation requires a critical β value that increases with increasing σ0 and decreasing L0. Despite the unavailability of observations in the existing literatures to check the condition of magnetic dip formation, such condition will be checked against observations as a future study. Finally, we also use 3‐D ring current‐atmosphere interactions model with self‐consistent magnetic field model to illustrate the effect of azimuthal pressure distribution, which is relevant to asymmetric ring current.

Implications of using chemical dispersants to combat oil spills in the German Bight – Depiction by means of a Bayesian network

Application of chemical dispersants is one option for combatting oil spills, dispersing oil into the water column and thereby reducing potential pollution to coastal areas. Efficiency of dispersant application depends on oil characteristics, sea and weather conditions. Potential environmental impacts must also be taken into account. Referring to the German Bight region (North Sea), we show how probabilistic Bayesian network (BN) technology can integrate all these aspects to support contingency planning. Expected effects of chemical dispersion on oil spill drift paths are quantified based on comprehensive numerical ensemble simulations. Ecological impacts are represented just in simplified terms focusing on nearshore seabird distributions. The intuitive and interactive BN summarizes expected benefits from chemical dispersion depending on where and under which weather conditions a hypothetical pollution occurs.

Whole-Genome Resequencing of a Worldwide Collection of Rapeseed Accessions Reveals the Genetic Basis of Ecotype Divergence

Rapeseed (Brassica napus), an important oilseed crop, has adapted to diverse climate zones and latitudes by forming three main ecotype groups, namely winter, semi-winter, and spring types. However, genetic variations underlying the divergence of these ecotypes are largely unknown. Here, we report the global pattern of genetic polymorphisms in rapeseed determined by resequencing a worldwide collection of 991 germplasm accessions. A total of 5.56 and 5.53 million single-nucleotide polymorphisms (SNPs) as well as 1.86 and 1.92 million InDels were identified by mapping reads to the reference genomes of “Darmor-bzh” and “Tapidor,” respectively. We generated a map of allelic drift paths that shows splits and mixtures of the main populations, and revealed an asymmetric evolution of the two subgenomes of B. napus by calculating the genetic diversity and linkage disequilibrium parameters. Selective-sweep analysis revealed genetic changes in genes orthologous to those regulating various aspects of plant development and response to stresses. A genome-wide association study identified SNPs in the promoter regions of FLOWERING LOCUS T and FLOWERING LOCUS C orthologs that corresponded to the different rapeseed ecotype groups. Our study provides important insights into the genomic footprints of rapeseed evolution and flowering-time divergence among three ecotype groups, and will facilitate screening of molecular markers for accelerating rapeseed breeding.

Very long laser-induced graphitic pillars buried in single-crystal CVD-diamond for 3D detectors realization

The morphology, optical, spectroscopic and electrical characterization of mm-long graphite pillars created by picosecond pulsed laser irradiation (λ = 800 nm and 1 kHz of repetition rate), buried in single crystal CVD diamond to be employed as electrodes in a 3D diamond detector, is reported. The array of graphitized columns – 2.5 mm-long, with a diameter of ≈ 10 μm – consisted of two rows spaced by 110 μm with 12 pillars in each, which formed an interdigitated electrode structure embedded in the diamond crystal bulk. The presence of stressed regions along and between pillars were clearly shown with optical polarized microscopy, in a black field configuration. Confocal micro-Raman and photoluminescence analysis has been employed to scan local stresses, both generated around the graphitic wires and also developed on the pillars' plane. Defected/stressed regions with diameter of the order of 10 μm surrounding the individual pillars was measured, and paired carbon interstitials (3H defects) were also revealed. For the investigated structure, detrimental effects induced by such structural defects, clearly produced by laser-induced diamond-graphite transition, as well as the presence of a relatively high voltage drop along the graphitized pillars related to their own geometry have been reflected on the charge carriers collection performances evaluated under MeV β-particles. The creation of electronic active states within the diamond bandgap, as emphasized by spectral photoconductivity characterization, would play a fundamental role in lowering lifetime of generated carriers and then the detector collection efficiency. Indeed, states located in the middle of the diamond bandgap, acting as efficient recombination centers and decreasing the lifetime of generated carriers, drastically reduce the mean drift path of carriers and then the overall detector collection efficiency, as evaluated in the examined structure even at the highest applied voltages (up to 600 V).

MMS/FEEPS Observations of Electron Microinjections Due to Kelvin‐Helmholtz Waves and Flux Transfer Events: A Case Study

AbstractThe Energetic Particle Detector (EPD) suite onboard the Magnetospheric Multiscale (MMS) spacecraft observes dispersive and repetitive fluxes of high‐energy (50–400 keV) electrons within the Pc5 frequency band (2–8 MHz) in the dusk to midnight region of Earth's magnetotail. These microinjections are a new phenomenon in this region of the magnetosphere, presently poorly understood, but clearly a new signature that remotely senses large‐scale magnetospheric boundary dynamics. It is therefore important to understand their properties and driver mechanisms. Here we have combined global magnetohydrodynamic simulations and particle tracing results with the MMS EPD Fly's Eye Energetic Particle Spectrometer (FEEPS) observations to investigate possible origins and source regions of the electron microinjections. Our simulation results suggest that the electron microinjections, observed in the dusk to premidnight sector, are associated with Kelvin‐Helmholtz waves (KHWs) and flux transfer events (FTEs). Energetic electrons launched from a limited range of locations near the postnoon dusk magnetopause and at times when KHWs and FTEs pass by that region have drift paths that connect with MMS and thus create time‐dependent microinjection electron signatures. Test‐particle tracing results in the magnetohydrodynamic fields also support the field‐aligned nature of electron microinjections observed by MMS. Though identifying the mechanism by which KHWs and FTEs might periodically inject electrons is beyond the scope of this work, our study does identify these duskside magnetopause boundary phenomena as likely agents of microinjection origins.

100 GHz Plasmonic Photodetector

Photodetectors compatible with CMOS technology have shown great potential in implementing active silicon photonics circuits, yet current technologies are facing fundamental bandwidth limitations. Here, we propose and experimentally demonstrate for the first time a plasmonic photodetector achieving simultaneously record-high bandwidth beyond 100 GHz, an internal quantum efficiency of 36% and low footprint. High-speed data reception at 72 Gbit/s is demonstrated. Such superior performance is attributed to the subwavelength confinement of the optical energy in a photoconductive based plasmonic-germanium waveguide detector that enables shortest drift paths for photogenerated carriers and a very small resistance-capacitance product. In addition, the combination of plasmonic structures with absorbing semiconductors enables efficient and highest-speed photodetection. The proposed scheme may pave the way for a cost-efficient CMOS compatible and low temperature fabricated photodetector solution for photodetection b...

An early forecasting method for the drift path of green tides: A case study in the Yellow Sea, China

Since 2007, green tides caused by massive blooms of Enteromorpha prolifera have occurred in the Yellow Sea during April and September every year. Generally, the macroalgae first gathered around the Jiangsu coastline and then moved northeastward toward the Shandong Peninsula, but the paths and distribution of green tides have featured obvious inter-annual variation. Here, we describe a new method to forecasting the drift path of green tides with some climate indices such as Nino3.4. This method may help policy makers to develop a strategy to prevent green tide disasters and mitigate the consequence more effectively.Initially, we ran a numerical ocean model to simulate the movement of hypothetical green tides for last 20 years. The model was driven by remote sensing data of sea surface winds, surface temperatures, and tracers representing macroalgae that were created on certain dates so that drift paths could be traced. Ocean color remote sensing data were employed to determine the drift parameters. Next, the relationship between the displacement of tracers, including directions and distances of movement during certain periods were then analyzed along with the corresponding values of a set of six climate indices. A forecasting algorithm based on an artificial neural network was then established and trained with these data. Using this algorithm, the drift path of green tides could be predicted from the values of certain climate indices of the previous year. The model assessment with satellite ocean color remote sensing images indicated the effectiveness and practicability of this method.

Arctic sea ice is an important temporal sink and means of transport for microplastic

Microplastics (MP) are recognized as a growing environmental hazard and have been identified as far as the remote Polar Regions, with particularly high concentrations of microplastics in sea ice. Little is known regarding the horizontal variability of MP within sea ice and how the underlying water body affects MP composition during sea ice growth. Here we show that sea ice MP has no uniform polymer composition and that, depending on the growth region and drift paths of the sea ice, unique MP patterns can be observed in different sea ice horizons. Thus even in remote regions such as the Arctic Ocean, certain MP indicate the presence of localized sources. Increasing exploitation of Arctic resources will likely lead to a higher MP load in the Arctic sea ice and will enhance the release of MP in the areas of strong seasonal sea ice melt and the outflow gateways.

Experimental and simulation research on the screening effect of the pixelated CZT imaging detector

Massive efforts have been made to investigate the characteristics of the CdZnTe detector under different extreme conditions. In this paper, we experimented with different radiation sources to investigate the imaging screening effect of the pixelated CdZnTe detector under ultrahigh irradiance. A donut-shaped irradiation image was obtained due to the increase in the X-ray tube current or the tube voltage. Moreover, statistical data revealed that the total count of all pixels was not significantly different, while the event-count of irradiated area pixels decreased significantly. A consequence of the screening effect was that the event counts redistributed among pixels that are located in the irradiated area, while the inner electric field was distorted. This leads to the catastrophic performance degradation of the central pixels. According to the Poisson equation, we developed a theoretical model of the CdZnTe detector using the finite element software COMSOL to enable an in-depth investigation of carrier collection in the CdZnTe crystal. A comparison between the simulations and the test results showed that pixels in the central irradiated area are completely screened under the ultrahigh irradiance because of the emergence of the relatively higher potential region, which can distort the electron drift path. Furthermore, the photon-generated signal can be collected only partly at the edge of the irradiated area, which was relatively stable because the collection area in the CdZnTe volume was relatively limited. The imaging results deduced from the simulations are well consistent with the experimental data.

Occurrence Locations, Dipole Tilt Angle Effects, and Plasma Cloud Drift Paths of Polar Cap Neutral Density Anomalies

AbstractPolar cap neutral density anomaly (PCNDA) with large mass density enhancements over the background has been frequently observed in the polar cap during magnetic storms. By tracing field lines to the magnetosphere from the polar ionosphere, we divide the polar cap into two regions, an open field line (OFL) region with field lines connecting to the magnetopause boundary and a distant tail field line (TFL) region threaded with magnetotail lobe field lines. A statistical study of neutral density observed by the Challenging Minisatellite Payload satellite during major magnetic storms with Dst < −100 from July 2001 to 2006 indicates that over 85% of density anomalies were detected in the TFL region, at about 18° to 25° equatorward the center of the OFL region. PCNDAs were frequently accompanied by plasma clouds with peak density greater than 105 #/cm3. Modeling of plasma cloud drift paths suggests that plasma clouds originating in the dayside ionosphere could convect through the OFL region following the zero‐potential line and reach the PCNDA locations. Plasma clouds could become stagnate in the TFL region, allowing a long duration of collisions with the neutral gas and possibly contributing to heating of PCNDAs. The PCNDA observations are interpreted as evidence that traveling atmospheric disturbance could be generated in the nightside polar cap. From the PCNDA size and speed of sound at 400 km, we derive an initial energy deposition duration for producing traveling atmospheric disturbance in the range from 0.5 to 2.5 hr.

Influence of Atlantic Water on the Sea Ice Cover in the Western Arctic in Winter

The results of temperature and salinity measurements in the upper 1000-mlayer of the Nansen Basin in the Arctic Ocean made from the North Pole-35 drifting station in winter of 2007/2008 are analyzed. The uniqueness of the dataset processed is defined by the station drift path in the Nansen Basin and by the time of the drift which immediately followed the record decline of Arctic sea ice in September 2007. It is found that the maximum heat flux from the ocean to the ice cover equal to more than 90 W/m2 was observed in the area of Atlantic water in flow between Spitsbergen and Franz Josef Land. It was caused by the drift velocity increase and by the corresponding deepening of the Ekman boundary layer. No significant changes (as compared to climate normals) in the influence of ocean heat on the ice cover in the eastern Nansen Basin in winter were registered.

Pallid sturgeon larvae: The drift dispersion hypothesis

The fate of drifting pallid sturgeon larvae [Scaphirhynchus albus, Forbes and Richardson, 1905] from spawning in the Missouri River below Fort Peck Dam, Montana, USA remains in question. Previous estimates of drift duration used flow modeling and experimental releases of free embryo pallid sturgeon that were recaptured in nets at incremental distances downstream. The recapture studies hypothesized that the released larvae drift along the river bottom in an intact plume that flushes into the downstream reservoir where they die. Results were interpreted that nearly all drifting embryos would reach Sakakawea Reservoir (~375 river km downstream) in just 6 days, suggesting that there is insufficient drift distance for successful reproduction of pallid sturgeon. Those experiments recaptured less than 1% of the released larvae, thus the dispersal fate of the remaining ~99% of drifting larvae remains unknown. We hypothesized that the river is extremely dispersive due to complex channel bathymetry and flow, which spreads the plume of drifting particles bank to bank within a few kilometers downstream of the release location, and that the same would be true for drifting free embryos. This is referred to as the Drift Dispersion Hypothesis. This hypothesis was tested by conducting high-resolution 3D flow and depth mapping, spanning the width of the Missouri River for 338 km in coordination with an embryo release and recapture study conducted in June 2016. Fort Peck Dam discharge was stabilized for the experiment. Hydraulic base maps were used to calculate particle drift paths and estimate drift speeds in (i) the bottom boundary layer (0.5 m) and (ii) the whole water column, as a surrogate for drifting larvae. Drift path patterns indicated wide lateral dispersion across the river, bank to bank. Drift simulations indicated that less than 10% of the fastest drifting embryos could reach Sakakawea Reservoir in just 6.56 days, but only if they remained mid-column and in the channel thalweg the entire distance. However, the fastest drifting particles that remained in the bottom boundary layer would not reach Sakakawea Reservoir for 31 days. Concluded was that most drifting embryos must be swept from the thalweg into low velocity habitats and stall, extending their river residence time. Stall locations were recorded along the entire study reach. The results indicate that drift duration is not the limiting factor for pallid sturgeon recruitment when spawning occurs near the embryo release site downstream of Fort Peck Dam.

A New Approach to Increasing the Resolution of a Mass Spectrometer with Wedge-Shaped Reflectors

The paper describes the investigation of the ion-optical properties of a laser TOF mass spectrometer including two successively positioned wedge-shaped ion mirrors. Some specific properties of the configuration of ion trajectories near their reflection in the second ion reflector are found. The dependence of aberrations on ion energy acquired toothed shape for the resolution of the analyzer higher than 3000–5000. The approximation of the dependence gave a 15th degree polynomial. The calculation of polynomial coefficients showed a great contribution to the duration of ion packets for aberrations of higher order. The discovered features allowed us to suggest a way of the local correction of nearby trajectories in the total ion flux. By correcting the local motion of individual groups of ions, we could reduce temporary aberration to 1–1.6 ns, depending on ion energy. For the time of ion flight ~35 μs, such duration limits the resolution of the analyzer by a value not less than 10000. The real length of ion drift path was about 30 cm. The total overall sizes of the ionoptical system were ~24 × 19 × 5 cm.

The plasma environment inside geostationary orbit: A Van Allen Probes HOPE survey.

The two full precessions in local time completed by the Van Allen Probes enable global specification of the near‐equatorial inner magnetosphere plasma environment. Observations by the Helium‐Oxygen‐Proton‐Electron (HOPE) mass spectrometers provide detailed insight into the global spatial distribution of electrons, H+, He+, and O+. Near‐equatorial omnidirectional fluxes and abundance ratios at energies 0.1–30 keV are presented for 2 ≤ L ≤ 6 as a function of L shell, magnetic local time (MLT), and geomagnetic activity. We present a new tool built on the UBK modeling technique for classifying plasma sheet particle access to the inner magnetosphere. This new tool generates access maps for particles of constant energy for more direct comparison with in situ measurements, rather than the traditional constant μ presentation typically associated with UBK. We present for the first time inner magnetosphere abundances of O+ flux relative to H+ flux as a function of Kp, L, MLT, and energy. At L = 6, the O+/H+ ratio increases with increasing Kp, consistent with previous results. However, at L < 5 the O+/H+ ratio generally decreases with increasing Kp. We identify a new “afternoon bulge” plasma population enriched in 10 keV O+ and superenriched in 10 keV He+ that is present during quiet/moderate geomagnetic activity (Kp < 5) at ~1100–2000 MLT and L shell 2–4. Drift path modeling results are consistent with the narrow energy and approximate MLT location of this enhancement, but the underlying physics describing its formation, structure, and depletion during higher geomagnetic activity are currently not understood.

New nonlinear dynamic response model of squat/slender flanged/non‐flanged reinforced concrete walls

The response of reinforced concrete (RC) shear wall as a lateral resisting member has been studied extensively, but it still demands a general practical model that identifies the envelope within which load–drift paths occur during cyclic loading. Such a broad model is vital to ensure adequate lateral strength to resist reversal loadings imposed on these walls during earthquake events and ductility to measure inelastic deformation capabilities. A new model to define the backbone curve is developed in this paper for squat, intermediate, and slender flanged and non‐flanged RC walls. The most common failure modes observed in the field and laboratory experiments are investigated and incorporated in the proposed model to estimate the response of these walls from elastic range until ultimate failure. The main parameters controlling the estimation of drifts that features the backbone curve thresholds are presented in this paper. The results of proposed model are compared with the outcomes of 117 specimens experimentally tested by other researchers. Also, the results are compared with Federal Emergency Management Agency (FEMA) 356, the updated American Society of Civil Engineers (ASCE)/Structural Engineering Institute (SEI) 41, and Eurocode (EC8 and EC2) provisions which reveal that only one general model, proposed in this paper, can capture the response of RC structural walls with an aspect ratio ranging from 0.35 to 2.5 and an axial load ratio from 0 to 0.4 with good agreement with experimental outcomes.