Enhanced Ion Flux Research Articles

Analyzing the effects of helical flow in blood vessels using acoustofluidic-based dynamic flow generator

The effects of helical flow in a blood vessel are investigated in a dynamic flow generator using surface acoustic wave (SAW) in the microfluidic device. The SAW, generated by an interdigital transducer (IDT), induces acoustic streaming, resulting in a stable and consistent helical flow pattern in microscale channels. This approach allows rapid development of helical flow within the channel without directly contacting the medium. The precise design of the window enables the creation of distinct unidirectional vortices, which can be controlled by adjusting the amplitude of the SAW. Within this device, optimal operational parameters of the dynamic flow generator to preserve the integrity of endothelial cells are found, and in such settings, the actin filaments within the cells are aligned to the desired state. Our findings reveal that intracellular Ca2+ concentrations vary in response to flow conditions. Specifically, comparable maximum intensity and graphical patterns were observed between low-flow rate helical flow and high-flow rate Hagen-Poiseuille flow. These suggest that the cells respond to the helical flow through mechanosensitive ion channels. Finally, adherence of monocytes is effectively reduced under helical flow conditions in an inflammatory environment, highlighting the atheroprotective role of helical flow. Statement of SignificanceHelical flow in blood vessels is well known to prevent atherosclerosis. However, despite efforts to replicate helical flow in microscale channels, there is still a lack of in vitro models which can generate helical flow for analyzing its effects on the vascular system. In this study, we developed a method for generating steady and constant helical flow in microfluidic channel using acoustofluidic techniques. By utilizing this dynamic flow generator, we were able to observe the atheroprotective aspects of helical flow in vitro, including the enhancement of calcium ion flux and reduction of monocyte adhesion. This study paves the way for an in vitro model of dynamic cell culture and offers advanced investigation into helical flow in our circulatory system.

Asymmetric Nanoporous Alumina Membranes for Nanofluidic Osmotic Energy Conversion.

The potential of harnessing osmotic energy from the interaction between seawater and river water has been recognized as a promising, eco-friendly, renewable, and sustainable source of power. The reverse electrodialysis (RED) technology has gained significant interest for its ability to generate electricity by combining concentrated and diluted streams with different levels of salinity. Nanofluidic membranes with tailored ion transport dynamics enable efficient harvesting of renewable osmotic energy. In this regard, anodic aluminum oxide (AAO) membranes with abundant nanochannels provide a cost-effective nanofluidic platform to obtain structures with a high density of ordered pores. AAO can be utilized in constructing asymmetric composite membranes with enhanced ion flux and selectivity to improve output power generation. In this review, we first present the fundamental structure and properties of AAO, followed by summarizing the fabrication techniques for asymmetric membranes using AAO and other nanostructured materials. Subsequently, we discuss the materials employed in constructing asymmetric structures incorporating AAO while emphasizing how material selection and design can resist and promote efficient energy conversion. Finally, we provide an outlook on future applications and address the challenges that need to be overcome for successful osmotic energy conversion.

Scalable and interfacial gap‐free mixed matrix membranes for efficient anion separation

AbstractMixed matrix membranes (MMMs) are promising in ion separation due to the simple preparation process. However, traditional metal–organic framework and covalent organic framework fillers lack the solution processibility and show interfacial defects between polymer matrixes and fillers, resulting in unsatisfactory separation performance. Herein, a soluble porous organic cage (POC) (i.e., CC3) is used as the filler to fabricate a large scale (~2000 cm2) and interfacial gap‐free ionic polymer (HPABP)‐CC3 membrane by a facile co‐solvent casting and rapid crystallization method. The resultant HPABP‐CC3(15) membrane shows a high Cl− flux of 2.24 mol m−2 h−1 and a Cl−/SO42− selectivity of 12.67, which is 3.6 and 3.0 times that of the HPABP membrane, respectively. Moreover, the HPABP‐CC3 membranes possess excellent cyclic and long‐term stability during the electrodialysis process. Therefore, we provide a facile strategy to scale up POC MMMs with synergistically enhanced ion flux and selectivity and the possibility for potential industrial ion separations.

Enhancement of Ar Ion Flux on the Substrate by Heterogeneous Charge Transfer Collision of Ar Atom with He Ion in an Inductively Coupled Ar/He Plasma.

The understanding of ion dynamics in plasma applications has received significant attention. In this study, we examined these effects between He and Ar species, focusing on the Ar ion flux on the substrate. To control heterogeneous collisions, we varied the He addition rate at fixed chamber pressure and the chamber pressure at fixed Ar/He ratio in an inductively coupled Ar/He plasma source. Throughout the experiments, we maintained an electron density in the bulk plasma and plasma potential as a constant value by adjusting the RF power and applying an additional DC bias to eliminate any disturbances caused by the plasma. Our findings revealed that the addition of He enhances the Ar ion flux, despite a decrease in the Ar ion density at the plasma-sheath boundary due to the presence of He ions. Moreover, we found that this enhancement becomes more prominent with increasing pressure at a fixed He addition rate. These results suggest that the heterogeneous charge transfer collision between Ar atoms and He ions in the sheath region creates additional Ar ions, ultimately leading to an increased Ar ion flux on the substrate. This finding highlights the potential of utilizing heterogeneous charge transfer collisions to enhance ion flux in plasma processing, without the employment of additional equipment.

Energetic ion variations during substorm intervals using the Van Allen Probes data

The study investigates ion flux variations for the substorms in the inner magnetosphere. The effect of substorm-induced magnetic field dipolarization on the O+ and H+ ion flux is analysed for 22 events from the year 2018 using the Helium, Oxygen, Proton, and Electron (HOPE) Mass Spectrometer data on board the Van Allen Probes (VAP/RBSP) satellite. The clear dipolarization signatures are observed using the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) suite from the VAP. These observations provide evidence of the ion flux enhancement at 1–50 keV energy after the substorm onset, in particular, the energy range of 20–50 shows dominance. The typical characteristics of magnetic field dipolarization and its time scales are investigated. It is found that the O+ ion flux enhances greater in magnitude than H+ ion flux at energies 20–50 keV after the substorm onset. In addition to it, the correlation of these enhanced oxygen fluxes with the related interplanetary magnetic field (IMF) Bz, solar wind velocity (Vsw), and the auroral electrojet (AE) index are found good. The new results reports that the ion flux variation ratio shows the MLT dependence for different energy ranges and found that the peak of the O+/ H+ ion flux ratio centred near midnight for the energy range of 8–20 keV, whereas the O+/ H+ ion flux ratio of the energy 20–50 keV is high within the post-midnight. The possible mechanisms for the enhanced ion flux are discussed.

Spacecraft Potential Changes Associated With EMIC Waves in the Inner Magnetosphere

AbstractAlthough electromagnetic ion cyclotron (EMIC) waves are commonly observed in the magnetosphere and are believed to energize background cold ions, it is not clear whether EMIC waves play a significant role in determining spacecraft potential change. In this paper, we present two strong He‐band EMIC wave events observed by the Van Allen Probe‐B spacecraft inside the plasmasphere. One event occurred on 11 March 2016 when the spacecraft was on the dayside, and the other occurred on 9 October 2016 when the spacecraft was in the postmidnight sector. When a strong He‐band EMIC wave activity was detected, low‐energy ion flux enhancements occurred nearly simultaneously with the EMIC wave power enhancements. Both events presented in this study are clearly unique in that He‐band wave power and enhanced proton flux are extremely high. During the wave activity interval, we found that the spacecraft charged more positively without a significant change in the ambient electron density. We discuss whether low‐energy ions energized by EMIC waves can contribute to the spacecraft potential change.

Mass Density Inferred From Toroidal Wave Frequencies and Energization of Low‐Energy Helium Ions During H‐Band EMIC Wave Interval

AbstractVan Allen Probe A observed strongly enhanced hydrogen (H+) band electromagnetic ion cyclotron (EMIC) waves lasting >6 hr without helium (He+) band EMIC wave activity outside the plasmasphere on 23 February 2014. During the H‐band EMIC wave interval, multiharmonic toroidal waves were detected by the spacecraft. We estimated the local mass density using the observed toroidal wave frequencies and background electron number density. It was found that the average ion mass is close to 1. This indicates that the protons are the dominant ion species for the H‐band wave interval. From these observations, we suggest that the cold ion composition plays a major role in determining the spectral properties of EMIC waves. We also observed low‐energy He+ ion flux enhancements associated with the H‐band EMIC waves in the direction perpendicular to the background magnetic field. We discuss how the H‐band waves energize the low‐energy He+ ions in the perpendicular direction.

In-situ growth of anionic covalent organic frameworks efficaciously enhanced the monovalent selectivity of anion exchange membranes

The development of monovalent selective ion exchange membranes with excellent performance is required owing to the continuous refinement of electrodialysis technology. Here, a tailored strategy for the in-situ growth of a sulfonate-rich covalent organic framework (sCOF) on the anion exchange membrane (AEM) was proposed to construct an ideal platform (sCOF/aAEM3) for superior anion separation. Specifically, sCOF and AEM were covalently linked (-C=N-) to ensure the high stability of the modified layer, which is an important application parameter. The sCOF layer, with a thickness of approximately 2.97 μm, was formed using the Bottom-Up in-situ growth method. The appearance of sulfonate in the pores of sCOF induced a strong electronegativity of −38.85 eV at pH = 7. The periodic structure of sCOF achieved a regularly sulfonate arrangement, which maximized the utilization of the functional group, causing strong electrostatic repulsion on SO42−. The electrodialysis process showed that sCOF/aAEM3 exhibited a superior perm-selective performance (PSO42−Cl− =18.92). In addition, the unique open 1D channel of sCOF endowed sCOF/aAEM3 with an enhanced ion flux of Cl− from 2.96 to 3.35 × 10−8 mol cm2 s−1. This facile strategy has been used for two other commercial AEMs having elevated perm-selectivity, which indicates the great potential for extensive applications.

Influence of ion irradiation-induced defects on phase formation and thermal stability of Ti0.27Al0.21N0.52 coatings

The influence of changes induced by ion irradiation on structure and thermal stability of metastable cubic (Ti,Al)N coatings deposited by cathodic arc evaporation is systematically investigated by correlating experiments and theory. Decreasing the nitrogen deposition pressure from 5.0 to 0.5 Pa results in an ion flux-enhancement by a factor of three and an increase of the average ion energy from 15 to 30 eV, causing the stress-free lattice parameter to expand from 4.170 to 4.206 Å, while the chemical composition of Ti0.27Al0.21N0.52 remains unchanged. The 0.9% lattice parameter increase is a consequence of formation of Frenkel pairs induced by ion bombardment, as revealed by density functional theory (DFT) simulations. The influence of the presence of Frenkel pairs on the thermal stability of metastable Ti0.27Al0.21N0.52 is investigated by scanning transmission electron microscopy, differential scanning calorimetry, atom probe tomography and in-situ synchrotron X-ray powder diffraction. It is demonstrated that the ion flux and ion energy induced formation of Frenkel pairs increases the thermal stability as the Al diffusion enabled crystallization of the wurtzite solid solution is retarded. This can be rationalized by DFT predictions since the presence of Frenkel pairs increases the activation energy for Al diffusion by up to 142%. Hence, the thermal stability enhancement is caused by a hitherto unreported mechanism - the Frenkel pair impeded Al mobility and thereby retarded formation of wurtzite solid solution.

Multi-spacecraft observations of the structure of the sheath of an interplanetary coronal mass ejection and related energetic ion enhancement

Context. Sheath regions ahead of coronal mass ejections (CMEs) are large-scale heliospheric structures that form gradually with CME expansion and propagation from the Sun. Turbulent and compressed sheaths could contribute to the acceleration of charged particles in the corona and in interplanetary space, but the relation of their internal structure to the particle energization process is still a relatively little studied subject. In particular, the role of sheaths in accelerating particles when the shock Mach number is low is a significant open research problem. Aims. This work seeks to provide new insights on the internal structure of CME-driven sheaths with regard to energetic particle enhancements. A good opportunity to achieve this aim was provided by multi-point, in-situ observations of a sheath region made by radially aligned spacecraft at 0.8 and ∼1 AU (Solar Orbiter, the L1 spacecraft Wind and ACE, and BepiColombo) on April 19−21, 2020. The sheath was preceded by a weak and slowly propagating fast-mode shock. Methods. We apply a range of analysis techniques to in situ magnetic field, plasma and particle observations. The study focuses on smaller scale sheath structures and magnetic field fluctuations that coincide with energetic ion enhancements. Results. Energetic ion enhancements were identified in the sheath, but at different locations within the sheath structure at Solar Orbiter and L1. Magnetic fluctuation amplitudes at inertial-range scales increased in the sheath relative to the solar wind upstream of the shock, as is typically observed. However, when normalised to the local mean field, fluctuation amplitudes did not increase significantly; magnetic compressibility of fluctuation also did not increase within the sheath. Various substructures were found to be embedded within the sheath at the different spacecraft, including multiple heliospheric current sheet (HCS) crossings and a small-scale flux rope. At L1, the ion flux enhancement was associated with the HCS crossings, while at Solar Orbiter, the ion enhancement occurred within a compressed, small-scale flux rope. Conclusions. Several internal smaller-scale substructures and clear difference in their occurrence and properties between the used spacecraft was identified within the analyzed CME-driven sheath. These substructures are favourable locations for the energization of charged particles in interplanetary space. In particular, substructures that are swept from the upstream solar wind and compressed into the sheath can act as effective acceleration sites. A possible acceleration mechanism is betatron acceleration associated with a small-scale flux rope and warped HCS compressed in the sheath, while the contribution of shock acceleration to the latter cannot be excluded.

Action-potential-inspired osmotic power generation nanochannels

The action potential across biological membranes formed by osmotic gradient induced by external conditions plays a key role in the signal transmission of life processes, which can inspire researchers to develop artificial osmotic power generation device with multi-stimuli controllable power output. Herein, an adaptive 2D nanochannel membrane is fabricated by stacking of montmorillonite nanosheets co-modified with a laboratory synthesized cationic surfactant containing spiropyran species and a commercially cationic surfactant of dioctadecyldimethylammonium bromide. Similar to biological action potentials, the osmotic power generation of 2D nanochannel membranes can be regulated by external multiple stimuli such as light, pH and temperature based on the adaptive ion selectivity and ion flux of nanofluidic channels relying on the surface charges of spiropyran species and the phase state of surfactants. Impressively, the control of temperature rising to 60 °C significantly boosted the maximum power density of 2D nanochannel membrane from ∼0.81 W/m2 to be ∼7.12 W/m2 by 8.8 times at a gradient of artificial sea water and river water resulting from the enhanced ion flux by phase transition of surfactants, which is the highest value among those of clay-based nanochannel membranes and ion exchange membranes. Our results implies that the development of adaptive 2D nanochannel membranes is a new strategy for improving the power output of osmotic energy conversion devices.

A Statistical Study of Low‐Energy Ion Flux Enhancements by EMIC Waves in the Inner Magnetosphere

AbstractWe have studied the statistical properties of low‐energy proton (H+) and helium (He+) ion flux enhancements associated with electromagnetic ion cyclotron (EMIC) waves in the inner magnetosphere using Van Allen Probes data for 2013–2017. We identified 167 low‐energy ion flux enhancements when the EMIC waves occurred in a He‐band or in a multiple band (H‐band and He‐band) with strong He‐band and weak H‐band wave activity and found that most of them occurred from the noon to the premidnight sector near the magnetic equator just inside the plasmapause. Of 167 flux enhancement events, 68 exhibited only He+ flux enhancements, and 99 exhibited both H+ and He+ flux enhancements. The EMIC wave‐associated flux enhancement events are mostly energized in the direction perpendicular to the background magnetic field. When both H+ and He+ fluxes are simultaneously enhanced, the H+ flux events have a peak energy distributed in the range of 2–100 eV, and the peak energies of the He+ flux events are distributed in the 2–600 eV range, implying that the helium ions are more energized than the protons. The peak energies of only He+ flux enhancement without H+ flux enhancement are mostly distributed in a lower energy range, 2–10 eV. The energization of H+ and He+ ions can be explained by a linear plasma flow associated with EMIC waves. We suggest that the wave‐associated linear plasma motion is a likely mechanism to explain the observations.

The Link Between Wedge‐Like and Nose‐Like Ion Spectral Structures in the Inner Magnetosphere

AbstractThe wedge‐like and nose‐like ion spectral structures, named after their characteristic shapes in the energy‐time spectrograms, appear to be distinctively different structures in the Earth's inner magnetosphere. Here. we present a case study with conjugate observations from the Arase spacecraft and the twin Van Allen Probes on July 1 and 2, 2017, which displayed the characteristic signatures of the wedge‐like and nose‐like ion structures, respectively. When the spacecraft nearly intersected at L = 2.8, the two structures overlapped with enhanced ion fluxes in the energy range of 1–10 keV. These observations suggest that the wedge‐like and nose‐like spectral signatures are merely the manifestations of one single structure along different spacecraft trajectories. This finding is further validated by the reproduction of both structures from a particle‐tracing model, which also indicates their formation processes associated with the intermittent substorm injections in the nightside magnetosphere.

Energy Modulations of Magnetospheric Ions Induced by Foreshock Transient‐Driven Ultralow‐Frequency Waves

AbstractAlthough foreshock transients can generate strong magnetospheric Pc5 ultralow‐frequency (ULF) waves, whether they can modulate the energy of magnetospheric ions is still poorly understood. In this study, we analyze the strong magnetospheric ion energy modulations in a foreshock transient event on October 30, 2008, based on the magnetospheric observations by the time history of events and macroscale interactions during substorms A and D in the prenoon sector. ULF wave‐induced drift accelerated the cold ions up to ∼10 keV and the enhanced ion fluxes have wave‐like patterns. There is another portion of enhanced ion fluxes from ∼0.8 to ∼10 keV but with strong energy dispersions in this event. By comparing the observations and the theoretical prediction, we for the first time found that the drift‐bounce resonances played a major role in modulating the energy of those ions with energy dispersions, during the interactions between the ions and the foreshock transient‐driven Pc5 ULF wave with growing and damping effects.

Magnetotail Dipolarizations and Ion Flux Variations During the Main Phase of Magnetic Storms

AbstractNear‐Earth tail dipolarizations are usually associated with fast plasma flows and an increase in energetic particle fluxes. Yet, the role of these dipolarizations in energetic ion flux transport toward the inner magnetosphere and in ring current (including partial ring current) development during the main phase of a geomagnetic storm is not fully understood. We investigated observations from Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes A, D, and E with apogees at X ≈ −13 RE and Los Alamos National Laboratory (LANL) geosynchronous spacecraft in the midnight magnetic local time (MLT) sector (21.5–1.5 h MLT) during the main phases of storms with integrated Dst exceeding 600 nT*hr from the 2010 to 2016 THEMIS tail seasons. We selected 10 storms during which at least one of the THEMIS probes was in the midnight sector during a storm’s main phase and identified 39 dipolarization events with a Bz increase exceeding 10 nT within 500 s during these storms’ main phases. In 21 of the 39 events, an increase in the magnetic field elevation angle Θ estimated from LANL magnetospheric plasma analyzer (MPA) data was detected at geosynchronous orbit (GEO) within ±15‐min‐long time window around dipolarization onset detected by THEMIS. In only 10 of those 21 events, however, did ion fluxes at energies from 50 to 500 keV increase in three or more consecutive energy bins at LANL. Comparisons of ion spectra collected by THEMIS and LANL in these 10 events revealed a similar increase in fluxes at energies E > 20 keV. Our results indicate that a dipolarization that occupies a large portion of the nightside magnetosphere from GEO to ∼12 RE is a necessary but not sufficient condition for energetic ion flux enhancements at GEO. As suggested in previous studies, an increase in the azimuthal electric field (i.e., enhanced earthward magnetic flux transport) is most likely required for an ∼100 keV ion flux increase at GEO.

Observations of Density Cavities and Associated Warm Ion Flux Enhancements in the Inner Magnetosphere

AbstractWe present a statistical study of density cavities observed in the inner magnetosphere by the Van Allen Probes during four one‐month periods: February 2013, July 2013, January 2014, and June 2014. These periods were chosen to allow the survey of all magnetic local times. We find that density cavities are a recurrent feature of the density profiles of in situ measurements in the inner magnetosphere. We further investigate the correlation between the density cavities and the enhancement of fluxes of warm ions with energies of 10–100 eV. The results show that warm ion flux enhancements associated with the density cavities were observed more frequently for H+, then for He+ and the least frequently for O+. The occurrences of the associated flux enhancements were increased when considering only the cavities inside the plasmasphere. Possible mechanisms responsible for the observed warm ion flux enhancements and the role of density cavities on these ion flux enhancements are discussed.

Coronagraphic observations of the lunar sodium exosphere 2018–2019

Remote observations of the lunar sodium corona have been obtained with the Goddard Lunar Coronagraph located at the Winer Observatory in Sonoita, Arizona. We previously reported the results of observations in the spring, 2017, observing season (Killen et al., 2019). We report herein the results of the 2018–2019 observing campaign. We show definitive effects on the corona - the extended lunar sodium exosphere above 150 km from the surface - of enhanced ion flux onto the Moon as measured by the ARTEMIS ElectroStatic Analyzer. The three observations in this dataset with the largest column abundances are associated with entrance of the Moon into the magnetosheath. The enhancement in the exosphere due to ion flux is not long-lived after the enhanced ion influx decreases, confirming the findings of Killen et al., 2012. The column abundance is greatest at both the dawn and dusk terminators as predicted and simulated by Smyth and Marconi, 1995. The cause of the increased scale height at the terminators is consistent with radiation pressure acceleration anti-sunward. We report a shallow decline of column abundance with increasing latitude which is also consistent with radiation pressure acceleration. Most of our measured scale heights are on the order of 800–1800 km, increasing at high latitudes, consistent with the data set published in Killen et al., 2019. Although the intensity extrapolated to the surface decreases with latitude, the scale height increases with latitude, so that the exospheric column decreases more slowly with increasing latitude than does a cosine function.

Anisotropic Vorticity Within Bursty Bulk Flow Turbulence

AbstractUtilizing Magnetospheric Multiscale (MMS) observation in the tail plasma sheet, we study the vorticity field (ω = ∇ × V) of the plasma bulk (convective) velocity within the bursty bulk flow (BBF) in detailed. Two typical events are presented. In the event on 25 June 2017, Ey is the main component. In the other event on 6 July 2017, Ez is the main component. For both cases, the BBF electric field is dominated by the convective electric field (Ec = − V × B). Our case studies show clearly the existence of the convective vorticity field within the BBF. The vorticity field has prominent anisotropy (quantified by the anisotropic angle (θaa = arctan(ω⊥/ω∥)). More often, the BBF ω field has stronger perpendicular vorticity (ω⊥) than the parallel vorticity (ω∥). The dominance of vorticity by ω⊥‐dominating BBF is confirmed in the statistical sense. In particular, event on 25 June shows the significant evolution of the ion flux energy with the strength of the ω field. The strong ω field corresponds to the ion flux enhancement at high energy (above 10 keV), while the weak ω field corresponds to the ion flux enhancement at medium energy (2–5 keV). Investigation of the subset of channel from fast plasma investigation partial moment measurement reveals that the ion behaviors in the strong and decayed BBFs are distinctly different. The channeled ions form the narrow band distribution in the strong BBF but the multiple‐layer distribution in the weak BBF. Finally, spectrum analysis indicates that the BBF ω⊥ and ω∥ have a similar scaling about −2.0 (below 0.2 Hz).

Enhancement of ion energy and flux by the influence of magnetic reconnection in foam targets

Laser-driven ion acceleration attracts large attention due to variety of applications. In order to enhance accelerated proton energy and flux, we investigate the influence of laser-driven relativistic magnetic reconnection on the ion acceleration processes. In this relativistic regime, the longitudinal electric field becomes significantly enhanced and plays an important role in charged particle acceleration. To realize conditions for the magnetic reconnection, two spatially separated relativistic laser beams were used. The results obtained show a shift of high energy proton propagation direction compare to that corresponding to the target normal sheath acceleration scenario as well as enhancement in proton flux.

Oxygen Ion Butterfly Distributions Observed in a Magnetotail Dipolarizing Flux Bundle

AbstractCluster observed two intermittent oxygen ion (O+) flux enhancements with energy dispersions in a dipolarizing flux bundle, which is known as a region of enhanced northward magnetic field (Bz) embedded in the earthward high‐speed flow. The flux enhancements of O+ show clear pitch angle dependences, which are termed as butterfly distributions. Two corresponding flux enhancements of field‐aligned protons (H+) are also shown in its spectrum, but they are weaker and emerge later (~10 s) than those of O+. Simulation shows that both enhanced ion species are the counterstreaming populations. They originated from the lobe region and were driven into the center plasma sheet by the dawn‐dusk electric field (Ey). Backward tracing test‐particle simulations reproduce the butterfly O+ and the counterstreaming H+ distribution. The differences between O+ and H+ are because of their different gyroradii. The lobe O+ can arrive at the magnetic equatorial plane in less than one gyromotion due to its large gyroradius, and O+ with a larger field‐aligned velocity can arrive at the equatorial plane earlier, leading to the energy and pitch angle dependence. While H+ with similar energy can drift into dipolarizing flux bundle through electric field drift (E × B motion) and arrive at the equatorial plane through adiabatic motion, which consequently forms the field‐aligned flux enhancements in dipolarizing flux bundle, that is, the Bz‐dominant region. The simulation further confirms that intermittent increases of Ey component can produce the two intermittent flux enhancements, as indicated in the in situ observation.