Ion Drift Research Articles

Voltage controlled awakening of memristor-like dynamic current–voltage loops of ferroelectric triglycine sulfate

For the study of polarization reversal features in the structure of "mixed ionic-electronic conductor - on - ferroelectric" type, the hydrogen bonded molecular ferroelectric crystal triglycine sulphate (TGS) is used. The dynamic currant-voltage (I-V-) loops of thin TGS plates of polar (010) cut with dissimilar electrodes on the opposite surfaces (vacuum deposited Ag and Ag-paste diluted with a water-ethanol mixture) are investigated. After electroforming in the low-voltage vicinity of coercive voltage, during further cycling, a reversible transformation of I-V-loop shape occurs from typical of non-linear dielectrics to typical of memristive systems and than to typical of ferroelectrics (and vice versa) with a sequential increase (decrease) of drawing voltage amplitude. Such "awakening" and "falling asleep" of I-V-loops of the memristor type is apparently associated with reversible electromigration and accumulation of charged species (e.g., protons), in the hydrated surface layer of TGS as a component of electrochemical capacitor-on-ferroelectric structure. The observed transformation can be explained by considering the coupled ion transfer and polarization reversal taking into account the swinging of the boundary of the built-in chemical inhomogeneity under conditions of linear and/or nonlinear dynamics of ion drift and ionic concentration polarization caused by charged species transfer under the applied voltage.

ASHLEY: A New Empirical Model for the High‐Latitude Electron Precipitation and Electric Field

AbstractIn this study, a new high‐latitude empirical model is introduced, named for Auroral energy Spectrum and High‐Latitude Electric field variabilitY (ASHLEY). This model improves specifications of soft electron precipitations and electric field variability that are not well represented in existing high‐latitude empirical models. ASHLEY consists of three components, ASHLEY‐A, ASHLEY‐E, and ASHLEY‐Evar, which are developed based on the electron precipitation and bulk ion drift measurements from the Defense Meteorological Satellite Program (DMSP) satellites during the most recent solar cycle. On the one hand, unlike most existing high‐latitude electron precipitation models, which have assumptions about the energy spectrum of incident electrons, the electron precipitation component of ASHLEY, ASHLEY‐A, provides the differential energy fluxes in the 19 DMSP energy channels under different geophysical conditions without making any assumptions about the energy spectrum. It has been found that the relaxation of spectral assumptions significantly improves soft electron precipitation specifications with respect to a Maxwellian spectrum (up to several orders of magnitude). On the other hand, ASHLEY provides consistent mean electric field and electric field variability under different geophysical conditions by ASHLEY‐E and ASHLEY‐Evar components, respectively. This is different from most existing electric field models which only focus on the large‐scale mean electric field and ignore the electric field variability. Furthermore, the consistency between the electric field and electron precipitation is better taken into account in ASHLEY.

First Simultaneous Observation of STEVE and SAR Arc Combining Data From Citizen Scientists, 630.0 nm All‐Sky Images, and Satellites

AbstractOn September 28, 2017 citizen scientist observations at Alberta, Canada (51°N, 113° W) detected aurora and a thin east‐west purplish arc, known as strong thermal emission velocity enhancement (STEVE) that lasted less than 20 min. All‐sky imagers at subauroral latitudes measured stable auroral red (SAR) arcs during the entire night. The imager at Bridger, MT (45.3°N, 108.9°W) also measured a STEVE. The overlapping geometry allowed to determine that the height of STEVE was 225–275 km. STEVE is brighter in the 630.0 nm images in the West and almost merges with the SAR arc in the East. A DMSP satellite pass in the southern hemisphere was at the conjugate location of the Bridger imager during the STEVE observation. When mapped into the northern hemisphere intense subauroral ion drift and subauroral polarization streams were detected associated with the two optical signatures measured in 630.0 nm.

Effective collisional cross-section of small ions in the gas phase: Application to ion mobility spectrometry.

The observed drift times of monoatomic ions, including alkali metal ions and halide anions, are not fully consistent with their size. When the effect of mass is included through the Mason-Schamp equation, the deviation gets worse so that the trend of the experimental collisional cross-sections becomes completely opposite to what is expected. This is attributed to the stronger local electric field around smaller ions. The strong electric field in the vicinity of a small ion leads to strong ion-neutral interactions and creates a drag force against ion motion. The smaller the ions, the stronger the interaction, because of the higher charge density. In view of this, a modified equation is introduced to describe the relationship between the observed drift times or ion mobilities and the cross-sections of small ions. Here, for small ions with high charge density, the experimental collision cross-section is expressed as the effective collision cross-section, Ωeff = σi (1 + α/ri 3 ), that takes into account both intrinsic ion size, σi , and the ion-molecule interactions through a correction term of α/ri 3 , which is proportional to the charge density. A linear fit of the drift times of alkali metal ions and halide anions to the proposed equation showed relative deviations of <8.2%. The model successfully predicted the drift time of other small diatomic ions with reasonable error. The proposed model can be used as a simple and efficient relationship in predicting the effective cross-section of small ions.

On the Species Dependence of Ion Escapes Across the Magnetopause

AbstractRecent observations and particle‐tracing models have revealed a counterintuitive difference between the behaviors of magnetospheric protons and oxygen ions when they encounter the magnetopause. The oxygen ions usually meander around the magnetopause without a full escape to the magnetosheath, whereas the protons can more easily stream across the magnetopause despite their smaller gyroradii. Here, we analytically identify the mechanisms that cause this species dependence. As magnetospheric ions drift toward the magnetopause, the grazing angle of their magnetopause encounter is constrained within a narrow range near 0°, with its maximum being proportional to the square root of the ion gyroradius. It is the grazing angle that largely determines the follow‐up ion motion. The ions with larger grazing angles would meander around the magnetopause, whereas the meandering motion for ions with smaller grazing angles could be easily disrupted to enable their escape even if the normal magnetic field is very weak.

Measurement of E × B drift of impurities in the C-2W inner divertor using spatial heterodyne spectroscopy.

Edge control in the C-2W field-reversed configuration experiment is crucial for the stability and energy confinement of the core plasma. Such edge control is achieved by electrical biasing on the end-on electrode plates. The radial electric field generated by the electrode biasing can be measured by E × B induced drift of impurity ions. Spatial heterodyne spectroscopy (SHS) is a promising method of high light throughput spectroscopy. Doppler shifted spectra of O4+ ion emission lines have been measured using a novel, in-house built SHS system. The electric field in the jet plasma inside the inner divertor of C-2W was estimated using the temporal profile of the rotational velocity of the oxygen ions. SHS system details, obtained measurements, and the methods of improving the system performance will be discussed.

Atmospheric diffuse plasma jet formation from positive-pseudo-streamer and negative pulseless glow discharges

Atmospheric gas discharge is very likely to constrict into filaments and diffuse plasma formation is inefficient in most cases. Developing cost-efficient atmospheric diffuse plasma devices represents a significant challenge for high performance in biomedical decontamination and material processing. Here, we propose an alternative roadmap to produce a diffuse argon plasma jet by expanding and quenching the existing filamentary discharge at the initial or middle stage of streamer development. Possible mechanisms are summarized. With the gas flow velocity comparable to the ion drift one, enhancing ambipolar diffusion near the edge of the positive-streamer channel promotes the radial diffusion of newly-produced electrons, realizing the radial expansion of channel. Weakening electric field in front of the streamer head through head expansion and field offset, prevents the further development of streamer, leading to a positive-pseudo-streamer discharge. Reducing electric field in front of the negative-streamer head through ion compensation, impedes the initial growth of streamer, resulting in a negative pulseless glow discharge. The positive-pseudo-streamer and negative pulseless glow discharges function together to form the diffuse plasma jet.

Resolving Power and Collision Cross Section Measurement Accuracy of a Prototype High-Resolution Ion Mobility Platform Incorporating Structures for Lossless Ion Manipulation.

A production prototype structures for lossless ion manipulation ion mobility (SLIM IM) platform interfaced to a commercial high-resolution mass spectrometer (MS) is described. The SLIM IM implements the traveling wave ion mobility technique across a ∼13m path length for high-resolution IM (HRIM) separations. The resolving power (CCS/ΔCCS) of the SLIM IM stage was benchmarked across various parameters (traveling wave speeds, amplitudes, and waveforms), and results indicated that resolving powers in excess of 200 can be accessed for a broad range of masses. For several cases, resolving powers greater than 300 were achieved, notably under wave conditions where ions transition from a nonselective "surfing" motion to a mobility-selective ion drift, that corresponded to ion speeds approximately 30-70% of the traveling wave speed. The separation capabilities were evaluated on a series of isomeric and isobaric compounds that cannot be resolved by MS alone, including reversed-sequence peptides (SDGRG and GRGDS), triglyceride double-bond positional isomers (TG 3, 6, 9 and TG 6, 9, 12), trisaccharides (melezitose, raffinose, isomaltotriose, and maltotriose), and ganglioside lipids (GD1b and GD1a). The SLIM IM platform resolved the corresponding isomeric mixtures, which were unresolvable using the standard resolution of a drift-tube instrument (∼50). In general, the SLIM IM-MS platform is capable of resolving peaks separated by as little as ∼0.6% without the need to target a specific separation window or drift time. Low CCS measurement biases <0.5% were obtained under high resolving power conditions. Importantly, all the analytes surveyed are able to access high-resolution conditions (>200), demonstrating that this instrument is well-suited for broadband HRIM separations important in global untargeted applications.

Highly Sensitive Magnesium-Doped ZnO Nanorod pH Sensors Based on Electrolyte-Insulator-Semiconductor (EIS) Sensors.

For highly sensitive pH sensing, an electrolyte insulator semiconductor (EIS) device, based on ZnO nanorod-sensing membrane layers doped with magnesium, was proposed. ZnO nanorod samples prepared via a hydrothermal process with different Mg molar ratios (0–5%) were characterized to explore the impact of magnesium content on the structural and optical characteristics and sensing performance by X-ray diffraction analysis (XRD), atomic force microscopy (AFM), and photoluminescence (PL). The results indicated that the ZnO nanorods doped with 3% Mg had a high hydrogen ion sensitivity (83.77 mV/pH), linearity (96.06%), hysteresis (3 mV), and drift (0.218 mV/h) due to the improved crystalline quality and the surface hydroxyl group role of ZnO. In addition, the detection characteristics varied with the doping concentration and were suitable for developing biomedical detection applications with different detection elements.

Local Time Differences in the Ionospheric Electromagnetic Ion Cyclotron Waves during Storm Time

By using high-resolution (50 Hz) magnetic field observations from Swarm constellation, the temporal and spatial characteristics of Electromagnetic Ion Cyclotron (EMIC) waves in different local time sectors at mid-latitudes are investigated during the magnetic storm period of 16—25 March 2015. There are comparable number of EMIC wave events in the dawn and dusk sectors, while there are more EMIC wave events in the pre-noon sector than in the pre-midnight sector. The duskside preference is related to the plasmaspheric plume, while the dawnside preference is related to the enhanced solar wind dynamic pressure and dense cold plasma. The wave frequency in the dawn and pre-noon sectors is higher than that in the dusk and pre-midnight sectors, implying the local time difference in the source location and the ion composition. Most of the duskside events occur in the early recovery phase, while the dawnside events occur in the late recovery phase. The time difference comes from the time required for the westward drift of energetic ions and local time difference in the plasmapause position. H⁺ band waves are mainly found in the 06:00 MLT—10:00 MLT sector, while He⁺ band waves are mainly confined in the 18:00 MLT—22:00 MLT sector. There is no H⁺ band but a two band (He⁺ and O⁺) EMIC wave during the storm main phase, indicating the role of the dense oxygen ion in inhibiting the H⁺ band in the inner magnetosphere.

Nitric Oxide Ion Density Profiles in Earth's Nightside High‐Latitude E and F Region Ionosphere

AbstractTransport effects on nitric oxide (NO) ion density, NO+, in the presence of suprathermal electrons in the nighttime high‐latitude E and F regions of Earth's ionosphere are investigated numerically. Our model includes ion drift induced by neutral winds for the NO+. Ionization rates are obtained using a numerical Boltzmann equation solver for electron transport. Ions densities are obtained from the IRI2016 model while horizontal winds are based on observations. It is found that the altitudes where our modeled peak NO+ densities occur are in good agreement with observations. By including the radiative transfer model, local minima in NO+ density (troughs) are found to be sensitive to electron impact considered previously in chemical models.

Neutral Wind Dynamics Preceding the STEVE Occurrence and Their Possible Preconditioning Role in STEVE Formation

AbstractStrong Thermal Emission Velocity Enhancement (STEVE) is a nightsky optical phenomenon of great research interest in recent years. Recent findings indicated that STEVE likely represents certain extremely intensified chemiluminescence airglow instead of traditional aurora. In this study, we investigate the patterns and variations of the neutral wind and temperature before the STEVE emergence using joint scanning Doppler imager (SDI 630 nm) and optical all‐sky imager (ASI) observations, and make an initial effort to explore the potential preconditioning role of neutral winds in the STEVE production. Neutral winds enhance in westward and southward directions following substorm auroral intensification, and show an equatorward propagating trend from auroral latitudes. However, in STEVE events the enhanced equatorward winds feature a steep stop/reversal at certain subauroral latitude, and strong wind convergence is developed there. This pattern sustains for ∼15–20 min, and then STEVE arises at about this stop latitude. The strength of the southward wind intensification and wind convergence is in general weaker or absent in nonSTEVE substorm events. We propose that enhanced equatorward winds may transport relevant neutrals species that are key to the STEVE airglow production to subauroral latitudes, and pile up at the stop latitude of the equatorward winds due to the strong convergence there. Such a transport/pileup effect led by the neutral winds may prepare a reservoir of neutral constituent which, when further aided by subauroral ion drift, leads to a dramatic increase of the airglow production and the STEVE occurrence.

Implication of Tidal Forcing Effects on the Zonal Variation of Solstice Equatorial Plasma Bubbles

AbstractEquatorial plasma bubbles (EPBs) are plasma depletions that can occur in the nighttime ionospheric F region, causing scintillation in satellite navigation and communications signals. Past research has shown that EPB occurrence rates are higher during the equinoxes in most longitude zones. An exception is over the central Pacific and African sectors, where EPB activity has been found to maximize during solstice. Tsunoda et al. (2015) hypothesized that the solstice maxima in these two sectors could be driven by a zonal wavenumber 2 atmospheric tide in the lower thermosphere. In this study, we utilize satellite observations to examine evidence of such a wave‐2 feature preconditioning the nighttime ionosphere to favor higher EPB growth rates over these two regions. We find the postsunset total electron content (TEC) observed by FORMOSAT‐3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) during boreal summer from 2007 to 2012 exhibits a wave‐2 zonal distribution, consistent with elevated vertical plasma gradients favorable for EPB formation. Numerical experiments are also carried out to determine whether such an ionospheric wave‐2 can be produced as a result of vertical coupling from atmospheric tides with zonal wavenumber 2 in the local time frame. We find that forcing from these tidal components produced increases in the Rayleigh‐Taylor growth rate over both sectors during solar maximum and minimum, as well as wave‐2 modulations on vertical ion drift, ion flux convergence, and nighttime TEC. Our results are consistent with the aforementioned hypothesis over both regions with vertical coupling effects from atmospheric tides preconditioning the nighttime ionosphere to favor higher EPB growth rates.

Effect of resonant magnetic perturbations on local plasma current density gradients and neoclassical tearing modes

The effect of externally applied resonant magnetic perturbations (RMPs) on the local equilibrium plasma current density profile is studied numerically based on two-fluid equations in simplified cylindrical geometry. It is found that a moderate RMP below its penetration threshold, via non-linear mode coupling, induces a parallel electric field around its rational surface that can significantly change the local flux-surface-averaged current density gradient. At a given RMP amplitude, the modification of the current density profile increases with increasing electron temperature, and it significantly depends on the bi-normal electron fluid velocity at the resonant surface. The effect of this modification on the magnetic island growth is demonstrated by the example of small m/n = 2/1 islands (m/n being the poloidal/toroidal mode numbers), driven by an unfavorable plasma current density profile and bootstrap current perturbation. The 2/1 mode growth is stabilized by moderate static 4/2 or 6/3 RMPs if the local electron fluid velocity is in the ion drift direction or sufficiently large in the electron drift direction. These results reveal that a weakly three-dimensional equilibrium, containing a moderate 4/2 RMP and the associated shielding current, can be more stable against the 2/1 mode, which often causes tokamak plasma major disruptions.

Coupled drift and dust ion acoustic wave driven double layers in magnetized plasma with (r, q)-distributed electrons

The properties of coupled drift and dust ion acoustic wave (DIAW) driven nonlinear structures like solitary waves and double layers (DLs) are investigated in a magnetized inhomogeneous plasma carrying temperature and density inhomogeneities along with stationary dust. The electrons are assumed to follow double spectral index -distribution in which r shows the flat top nature while q is responsible for the shape of the distribution. A nonlinear differential equation is derived and its solution in the form of solitons and DLs is obtained by employing relevant boundary conditions. It is noted that coupled linear dust ion acoustic-drift wave and corresponding nonlinear structures are modified significantly under the variations in r and q. Only rarefactive solitons are obtained under the impact of various quantities especially r, q and normalized drift speed . However, both compressive and rarefactive double layers (DLs) are sustained/formed in such a plasma. It is noted in such an inhomogeneous, magnetized with non-Maxwellian character plasma that the amplitude of nonlinear structures is strongly dependent on the choice of parameters like r, q and . The study is important relevant to space plasmas.

Radar Observations of Flows Leading to Longitudinal Expansion of Substorm Onset Over Alaska

AbstractLongitudinal expansion of brightening of the substorm onset arc likely represents longitudinal expansion of the substorm onset instability. We used Poker Flat radar campaign auroral observations to identify seven substorm onsets seen east or west of the radar that expanded into the radar field‐of‐view. The radar observations were used to show flows relative to the expanding onset aurora. Flow enhancements were found equatorward (poleward) of the westward (eastward) longitudinal expansion of the onset arc brightening that agree with plasma sheet bubble modeling. This lends significant additional supporting evidence that an incoming reduced entropy flow channel leads to onset. As a flow channel enters the auroral oval (plasma sheet) from the polar cap (magnetotail lobes) and starts to move equatorward (earthward in the plasma sheet) as a bubble, it simultaneously expands azimuthally due to the combination of electric drift along dawnward tilted equipotentials and westward magnetic drift of more energetic ions. As the azimuthally expanding bubble reaches near the equatorward boundary of the electron auroral oval, it leads to the onset instability indicated by the auroral beading and associated flows if conditions are appropriate. The instability grows in the initial onset region, as it simultaneously extends longitudinally with the continued azimuthal expansion of the bubble within the plasma sheet. Additionally, after onset, the auroral bulge expands poleward and can lead to a westward traveling surge. We observe strong flows heading toward the front of the surge that appear to bring low entropy plasma, perhaps from the polar cap, into the surge.

Backward waves in the nonlinear regime of the Buneman instability

Observation of low- and high-frequency backward waves in the nonlinear regime of the Buneman instability is reported. Intense low-frequency backward waves propagating in the direction opposite to the electron drift (with respect to the ion population) of ions and electrons are found. The excitation of these waves is explained based on the linear theory for the stability of the electron velocity distribution function that is modified by nonlinear effects. In the nonlinear regime, the electron distribution exhibits a wide plateau formed by electron hole trapping and extends into the negative velocity region. It is shown that within the linear approach, the backward waves correspond to the weakly unstable or marginally stable modes generated by the large population of particles with negative velocities.

Ion Velocity and Temperature Variation Around Topside Nighttime Irregularities: Contrast Between Low- and Mid-Latitude Regions.

Studies on low-/mid-latitude ionospheric irregularities have a long history, but ion temperature and drift velocity variations within the irregularities have been rarely investigated, especially at mid-latitudes. To fill this knowledge gap, we statistically investigate ion temperature and velocity of mid-latitude ionospheric irregularities and compare them to those of low-latitude ones. This study mainly relies on in situ plasma moment data from the newly launched Ionospheric Connection Explorer (ICON) satellite and is supplemented by Republic of China Satellite 1 (ROCSAT-1) data in 2000-2004. At low latitudes (|MLAT|<10°) plasma density irregularities encountered by ICON have the following properties: lower-density regions have cooler ions and more poleward/westward/outward velocity than (|MLAT| = 10°∼30°), the opposite trends are observed: lower-density regions have hotter ions and more the ambient plasma, which agrees with previous reports on equatorial plasma bubbles. At mid-latitudes equatorward/eastward/inward drift than the ambient, which is a new finding in this study. The mid-latitude observations can be put into the context of Medium-Scale Traveling Ionospheric Disturbance (MSTID) properties reported previously, which evidences that topside irregularities at nighttime mid-latitudes generally represent MSTIDs. ROCSAT-1 data support the contrast between low- and mid-latitude ionospheric irregularities.

Investigating the Development of Distinctive Subauroral Flow Channels During the November 7–8, 2004 Superstorm

AbstractWe investigate the development of large (∼3,000 m/s) subauroral flows occurring during the November 7–8, 2004 Superstorm by utilizing multisatellite and multiinstrument measurements from the Magnetosphere (M), topside Ionosphere (I), and Thermosphere (T). We present eight scenarios (Sc‐1–Sc‐8) depicting the development of large SubAuroral Polarization Streams (SAPS) in the initial phase (Sc‐1–Sc‐3) and recovery phase (Sc‐5), and structured SAPS (Sc‐4, Sc‐6–Sc‐7) and Double‐peak SubAuroral Ion Drifts (DSAID) in the recovery phase (Sc‐8). Magnetospheric observations reveal dayside magnetopause reconnection increasing both the magnetospheric convection electric field and the large‐scale Field‐Aligned Currents (FACs), long‐lasting (∼5 h) secondary dipolarizations during the initial phase, and a series of dipolarization events during the recovery phase. Ionospheric observations reveal the development of these large subauroral flows (i) during forward and reverse plasma convections—when the topside ionosphere received earthward energy from the magnetosphere and when the diversion of cross‐tail currents in the stretched magnetotail activated the Substorm Current Wedge (SCW)—and (ii) in a short‐circuited system that acted as a voltage generator. Thermospheric observations reveal earthward energy deposition from the ionosphere that drove wind surges—implying the presence of Atmospheric Gravity Waves (AGWs) and Traveling Ionospheric Disturbances (TIDs)—propagating equatorward/poleward and passing through the trough region, and further enhancing the subauroral flows by deepening the trough. From these results we conclude that the strong M‐I‐T coupling occurring under superstorm conditions played a significant role in the enhancement of the subauroral flows investigated.

Data‐Driven Ensemble Modeling of Equatorial Ionospheric Electrodynamics: A Case Study During a Minor Storm Period Under Solar Minimum Conditions

AbstractThe dayside equatorial ionospheric electrodynamics exhibit strong variability driven simultaneously by highly changeable external forcings that originate from the solar extreme ultraviolet (EUV), magnetosphere, and lower atmosphere. We investigate this variability by carrying out comprehensive data‐driven ensemble modeling using a coupled model of the thermosphere and ionosphere, with the focus on the vertical E × B drift variability during a solar minimum and minor storm period. The variability of vertical E × B drift in response to the changes and uncertainty of primary forcings (i.e., solar EUV, high‐latitude plasma convection and auroral particle precipitation, and lower‐atmospheric tide and wave forcing) is investigated by ensemble forcing sensitivity experiments that incorporate data‐driven stochastic perturbations of these forcings into the model. Second, the impact of assimilating FORMOsa SATellite‐3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT‐3/COSMIC) electron density profiles (EDPs) on the reduction of uncertainty of the modeled vertical E × B drift variability resulting from inadequately specified external forcing is revealed. The Communication and Navigation Outage Forecasting System (C/NOFS) ion drift velocity observations are used for validation. The validation results support the importance of the use of a data‐driven forcing perturbation methods in ensemble modeling and data assimilation. In conclusion, the solar EUV dominates the global‐scale day‐to‐day variability, while the lower atmosphere tide and wave forcing is critical to determining the regional variability. The modeled vertical E × B drift is also sensitive to the magnetospheric forcing. The ensemble data assimilation of FORMOSAT‐3/COSMIC EDPs helps to reduce the uncertainty and improves agreement of the modeled vertical E × B drifts with C/NOFS observations.