Electromagnetic Drift Research Articles

25-26 Ağustos 2018 Jeomanyetik Fırtına Sırasında Afrika Bölgesi Üzerindeki Manyetik Eşlenik Çiftleri Üzerindeki TEC Değişikliklerinin İncelenmesi

In this study, the electron transport process resulting from electromagnetic drift between two magnetic conjugate pairs over the African region during the August 25-26 2018 geomagnetic storm was investigated. The effects of geomagnetic conditions presented with Dst index and IMF Bz values on Total Electron Content (TEC) values at conjugate stations were compared separately for stormy and quiet periods. During the storm period, the effect of TEC values at stations in the northern hemisphere (Haifa and Djibouti) on the TEC values at stations in the southern hemisphere (Ambalavao and Malindi) is greater than the effect of TEC values in the southern hemisphere on TEC values in the northern hemisphere. According to this result, it can be said that the south-directed electromagnetic convection was more than the north-directed convection in the examined dates. When the coefficients are examined, it can be said that the interaction is more in the magnetic conjugate pair that is closer to the equator during the storm period, and the interaction is more in the magnetic conjugate pair that is far from the equator during the silent period. Considering the coefficients calculated for Dst and IMF Bz, it is seen that the TEC values are very small compared to their coefficients. From this it can be concluded that the effect of Dst and IMF Bz is much smaller than the effect of TEC values at a station on TEC values at its magnetic conjugates.

Electromagnetic drift wave instability in tokamak plasmas with strong pedestal gradient

The linear eigenmode characterizations and the nonlinear turbulence energy spreading of the drift waves in a tokamak plasma with strong pedestal gradient are numerically investigated based on an electromagnetic Landau fluid model. By the linear eigenmode analysis, it is found that the dominant instability in the low β regime is the ion-temperature-gradient (ITGc) mode and the electron drift wave instability (eDWI p ) in the core and edge region with strong density gradient, respectively. Multiple eigenstates of the eDWI p with different peak locations in the poloidal direction can be obtained by the eigenvalue problem solver. The dominant one is the high order eDWI p corresponding to the unconventional ballooning mode structure with multiple peaks in the poloidal position, in contrast to the conventional modes that peak at the outboard mid-plane, and has been verified through initial value simulation. In the high β regime, the dominant eigenmodes in the core and edge region are the conventional and unconventional kinetic ballooning modes respectively. In the nonlinear simulation, an inward turbulence spreading phenomenon during the quasi-saturation phase of the edge turbulence is clearly observed. The inward speed of the turbulence energy front in the high β regime is much faster than that in the low β regime. It is interestingly found that the speed of the turbulence energy front increases with the increase of the plasma β in the low β regime, while it is almost unchanged in the high β regime. It is identified that the turbulence spreading in the low and high β regimes are determined by the nonlinear dynamics and the linear toroidal coupling respectively.

Propagatory dynamics of electromagnetic drift waves in inhomogeneous spin degenerate compact objects plasmas

A theoretical analysis is carried out to investigate the dynamics of electromagnetic drift modes in non-uniform spin quantum magnetoplasmas found in degenerate compact objects. General dispersion relations are derived using spin quantum hydrodynamic equations, Poisson equation, and Maxwell equation, with and without ion inertial effects. The effects of quantum spin magnetization, Bohm potential, and density inhomogeneity on the dispersion of electromagnetic drift modes are explored numerically. The advancing theoretical analysis demonstrated herein has strong correlations and consistencies with the dynamic growth of compact astrophysical objects and their surrounding atmospheres, such as black holes, white dwarfs, and dense molecular clouds.

INM-IM: INM RAS Earth ionosphere F region dynamical model

Abstract A new INM RAS global dynamical model of Earth’s ionosphere F region (100–500 km), which takes into account plasma-chemical processes, ambipolar diffusion, and advective ion transport due to electromagnetic drifts and neutral wind is presented. The model includes parameterizations of polar electric fields induced by magnetospheric convection and simplified equatorial drifts considerations. The focus of the paper is directed on the description of specific methods developed and utilized in the ionospheric model. Key processes responsible for the formation of global ionospheric features are outlined and their representation in the model is evaluated. The main global ionospheric characteristic features, such as seasonal and diurnal cycles, the equatorial ionization anomaly (EIA), polar ionization caps and the main trough have been adequately reproduced based on this model.

First Observation of Lower Hybrid Drift Waves at the Edge of the Current Sheet in the Martian Magnetotail

Lower hybrid drift waves are commonly observed at plasma boundaries, playing an important role in plasma dynamics. Such waves have been widely investigated in the terrestrial magnetosphere but have never been reported in other planetary environments. Here, using the measurements from the Mars Atmosphere and Volatile EvolutioN mission, we present the first observation of electromagnetic lower hybrid drift waves at the edge of the current sheet on the dusk side of the Martian magnetotail, which should be locally excited rather than propagated from other regions. These plasma waves are associated with significant density gradients and magnetic field gradients. Based on the measured local plasma parameters and the sufficient condition for lower hybrid drift instability to be excited, we find that the proton density gradient is sharp enough to excite the lower hybrid drift instability. The analysis of the existence condition for lower hybrid drift instability indicates that these lower hybrid drift waves at the edge of the current sheet are generated through lower hybrid drift instability. The above results can improve our understanding of Mars’ magnetospheric dynamics.

Effects of Coulomb collisions on lower hybrid drift waves inside a laboratory reconnection current sheet

We have developed a local, linear theoretical model for lower hybrid drift waves that can be used for plasmas in the weakly collisional regime. Two cases with typical plasma and field parameters for the current sheet of the magnetic reconnection experiment have been studied. For a case with a low electron beta (βe=0.25, high guide field case), the quasi-electrostatic lower hybrid drift wave is unstable, while the electromagnetic lower hybrid drift wave has a positive growth rate for a high-βe case (βe=8.9, low guide field case). For both cases, including the effects of Coulomb collisions reduces the growth rate but collisional impacts on the dispersion and growth rate are limited (≲20%).

Estimation of the Electric Field Zonal Component Value and Particle Transfer Velocity Due To Electromagnetic Drift in the Ionosphere during Magnetic Storm on September 25, 2016 over Kharkiv

Background. Dynamic processes in plasma play a significant role in the formation of the spatial structure of the ionosphere at altitudes above the main ionization maximum. During geomagnetic disturbances, the dynamic mode of the ionospheric plasma noticeably changes, and these changes in the variations in the physical process parameters directly affect the spatial-temporal distribution of the main parameters of the ionosphere. One of the mechanisms affecting the behavior of the dynamic process parameters in the ionosphere is the penetration of electric fields of magnetospheric origin into the mid-latitude ionosphere during magnetic storms. The effects of the electric field, which are practically absent in quiet conditions, during geomagnetic storms lead to an additional transfer of charged particles due to electromagnetic drift. Accounting for these effects in variations in the dynamic process parameters and, as a consequence, in variations in the parameters of the ionosphere, is necessary for a more adequate prediction of the behavior of geospace parameters during geomagnetic disturbances. Development of ionospheric models of the disturbed ionosphere for solving applied problems in the field of radio communication, radio navigation and uninterrupted operation of telecommunication systems for various purposes. The aim of this work is to estimate the magnitude of the zonal component of the electric field in the ionosphere over Kharkiv during a weak magnetic storm on September 25, 2016, as well as to calculate the neutral wind velocity taking into account plasma transport in crossed electric and magnetic fields. Materials and methods. To calculate the parameters of dynamic processes in the ionosphere, the experimental data of the Kharkiv incoherent scatter radar were used. Results. The value of the zonal component of the electric field Ey was calculated during a weak magnetic storm on September 25, 2016. The maximum value of Ey took place around 23:00 EEST on September 25, 2016 and was equal to 5.9 mV/m. Calculated values of particle transfer velocity due to electromagnetic drift vEB during the September 25, 2016 magnetic storm are obtained. Variations in vEB correlate with variations in Ey, and the maximum velocity was –52 m/s. The calculation results showed that during weak magnetic storms (Kp = 4) it is necessary to take into account the plasma transfer due to electromagnetic drift. The contribution of the velocity vEB to the total velocity of charged particle transfer is significant. The neutral (thermospheric) wind velocity vnx is calculated without and taking into account the particle transfer velocity in crossed electric and magnetic fields. Conclusions. As shown by the results of the comparative analysis, taking into account the influence of the electric field made it possible to refine the values of the velocities vnx during a magnetic storm, which, in turn, makes it possible to explain the behavior of the main parameters of the F2 layer of the ionosphere under disturbed conditions.

Dispersion relation for gauge-free electromagnetic drift kinetics

Recently, a new approach to gyrokinetics, invariant under electromagnetic gauge transformations, was developed. The gyrocenter equations of motion are now expressed in terms of the perturbed fields instead of the potentials, in a form suitable for numerical simulations and analytic studies. In this paper, we verify that the long-wavelength limit, i.e., the drift-kinetic limit of the new gyrokinetic theory, is in line with existing work, providing a solid foundation for simulations. We compute the dispersion relation of the new drift-kinetic theory in slab geometry and find agreement with a long-wavelength limit of the full Vlasov–Maxwell model.

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

To demonstrate the performance of tungsten (W) as the divertor target material and to solve the power handling problem during high power long-pulse discharge, the upgrade of EAST lower divertor is planned. In this work, the physical design of the W divertor is presented by using 2D edge plasma code SOLPS and Monte Carlo impurity transport code DIVIMP. The optimized divertor geometry is proposed after systematic examination of target shapes, target slant angles and the pump opening locations. The performance of the designed divertor is further assessed by impurity seeding. By comparing the medium and high power discharges with argon (Ar) seeding, the differences on the divertor power radiation and impurity core accumulation are distinguished. The simulated effective ion charge Z eff fits well the scaling law, which is based on multi-machine database. Ar seeding and neon (Ne) seeding scans are carried out separately. The simulation results indicate Ar has higher power radiation efficiency than that of Ne, thus promoting the achievement of plasma detachment. However, the core compatibility with Ar is worse than with Ne. The W target erosion and W impurity transport during impurity seeding are simulated by the DIVIMP–SOLPS coupled modeling. It illustrates that under the similar divertor plasma conditions, Ar seeding causes more serious W erosion and more severe core contamination by W impurity, than Ne seeding. Finally, the divertor in–out asymmetry is studied by considering electromagnetic drifts. The simulation results manifest that the designed open vertical inner target reduces in–out asymmetry due to that its weak power radiation capability is offset by the ion flow driven by the drifts. In addition, the designed divertor is compatible with the quasi snowflake magnetic configuration. These studies will improve the understanding of W target sputtering and W impurity transport control during the radiative divertor discharges for CFETR/DEMO.

Nonlinear Simulation of Ionospheric Irregularities at Mars

Abstract Motivated by the observations and linear theory analysis of ionospheric irregularities at Mars, we performed numerical simulations of the nonlinear evolution of the electromagnetic gradient drift instability in the Martian ionospheric dynamo region. The seeding source of ionospheric irregularities is perturbation zonal neutral wind. We found that the perturbation electric fields induced by the gradient drift instability can convect lower density plasma into higher density plasma at higher altitudes. Then, the associated perturbation magnetic field and electric field can cause the velocity shear of the plasma, which induced the Kelvin–Helmholtz instability at higher altitude. The Kelvin–Helmholtz instabilities furthermore lead to smaller-scale irregularities in plasma density, magnetic field, and electric field in the Martial ionosphere. Key points: (1) Nonlinear simulation of small-scale ionospheric irregularities at Mars was present. (2) Ionospheric irregularities at Mars can be seeded by the perturbation neutral winds. (3) Model results are comparable to linear theory analysis and satellite observations.

Constitutive relationship and governing physical properties for magnetophoresis

Magnetophoresis is an important physical process with application to drug delivery, biomedical imaging, separation, and mixing. Other than empirically, little is known about how the magnetic field and magnetic properties of a solution affect the flux of magnetic particles. A comprehensive explanation of these effects on the transport of magnetic particles has not been developed yet. Here we formulate a consistent, constitutive equation for the magnetophoretic flux of magnetic nanoparticles suspended in a medium exposed to a stationary magnetic field. The constitutive relationship accounts for contributions from magnetic diffusion, magnetic convection, residual magnetization, and electromagnetic drift. We discovered that the key physical properties governing the magnetophoresis are magnetic diffusion coefficient, magnetic velocity, and activity coefficient, which depend on relative magnetic energy and the molar magnetic susceptibility of particles. The constitutive equation also reveals previously unknown ballistic and diffusive limits for magnetophoresis wherein the paramagnetic particles either aggregate near the magnet or diffusive away from the magnet, respectively. In the diffusive limit, the particle concentration is linearly proportional to the relative magnetic energy of the suspension of paramagnetic particles. The region of the localization of paramagnetic particles near the magnet decreases with increasing the strength of the magnet. The dynamic accumulation of nanoparticles, measured as the thickness of the nanoparticle aggregate, near the magnet compares well with the theoretical prediction. The effect of convective mixing on the rate of magnetophoresis is also discussed for the magnetic targeting applications.

Electromagnetic Drift Waves at Substorm Onset: Theory and Observations

AbstractThe onset of a modest substorm observed by THEMIS is studied and interpreted using a new model of current sheet instability. The wave‐like structuring of the first observed auroral arc is characterized using auroral imagers. Similarly, the magnetic fluctuations measured by the THEMIS satellites, located in the near‐Earth current sheet (10 RE) and magnetically connected to the arc, are determined. Both sets of measurements show that oscillatory components with periods from 7 to 20 s are detected at the very early phase of the onset. This is compared with the predictions of a recent theoretical model (Tsareva et al., 2019, https://doi.org/10.1017/S002237781900028X) that describes the kinetic instability of electromagnetic drift waves in 2‐D Harris sheet configurations. They are in a reasonable agreement with the observations since the measured magnetic fluctuations are characterized by frequencies, growth rates, and polarization that are consistent with the model. It is also remarkable that the oscillations are observed when the ion perpendicular velocity (drift velocity) exceeds 90–100 km/s. The theory indeed shows that the drift is the main trigger of the instability, with a possible threshold at 80–100 km/s. This suggests that above a threshold of magnetic stress, and thus ion drift, the current sheet equilibrium is affected by the generation of electromagnetic drift waves.

Vertical plasma transport in the ionosphere over Irkutsk during St. Patrick’s Day geomagnetic storm: Observations and modeling

The St. Patrick’s Day storm being the strongest geomagnetic storm of Solar Cycle 24 caused strong changes in ionospheric and thermospheric dynamics. The paper presents a study of vertical plasma transport in the ionosphere during the St. Patrick’s Day storm with using both observations and modeling. The observations give the ionospheric peak height obtained with the chirp vertical sounding ionosonde and the neutral wind velocities obtained with the Fabry-Perot interferometer. The ionospheric peak height is an indicator of the total vertical plasma transport, while meridional wind and electromagnetic drift are the two main drivers of the vertical plasma transport. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere used in this study gives the total set of ionospheric and thermospheric parameters including F2-layer peak height, neutral wind velocities, electric field, and neutral composition. The model/data comparison allows us to obtain two main results. The first one is an estimation of the model prediction possibilities under storm conditions. The second result is an indirect assessment of the neutral wind and electric field contribution into the changes in the ionospheric peak height in the case of the St. Patrick’s Day geomagnetic storm.

Modelling of equatorial ionospheric anomaly in the INM RAS coupled thermosphere-ionosphere model

AbstractThe paper deals with the problem of the equatorial ionization anomaly (EIA) modelling and its representation in the global dynamical models of Earth’s ionosphere and thermosphere. A new version of the coupled thermosphere-ionosphere global dynamical model which reproduce the equatorial anomaly considerably well is presented. Key processes responsible for the EIA formation are outlined and their representation in the model is indicated. It was shown that the developed coupled thermosphere-ionosphere model with additional accounting of vertical electromagnetic drift at the equator realistically represents the EIA characteristics.

Magnetic Reconnection in Three Dimensions: Observations of Electromagnetic Drift Waves in the Adjacent Current Sheet

AbstractMagnetic reconnection at the subsolar magnetopause is persistently accompanied by strong fluctuations of the magnetic field (B), plasma density (n), and all components of the electric field (E) and current (J). The strongest fluctuations are at frequencies below the lower hybrid frequency and observed in a thin, intense current sheet adjacent to the electron diffusion region. In this current sheet, the background magnitudes of B and n are changing considerably, creating an inhomogeneous plasma environment. We show that the fluctuations in B and n are consistent with an oscillatory displacement of the current sheet in the surface normal direction. The displacement is propagating parallel to the magnetic reconnection X line. Wavelengths are on the order of or longer than the thickness of the current sheet to which they are confined, so we label these waves electromagnetic drift waves. E and J fluctuations are more complex than a simple displacement. They have significant variations in the component along B, which suggest that the drift waves also may be confined along B. The current sheet is supported by an electron drift driven by normal electric field, which, in turn, is balanced by an ion pressure gradient. We suggest that wave growth comes from an instability related to the drift between the electrons and ions. We discuss the possibility that drift waves can displace or penetrate into the electron diffusion region giving magnetic reconnection three‐dimensional structure. Drift waves may corrugate the X line, possibly breaking the X line and generating turbulence.

Electron‐Scale Magnetic Structure Observed Adjacent to an Electron Diffusion Region at the Dayside Magnetopause

AbstractIn this paper, we present observations made by the Magnetospheric Multiscale (MMS) mission of a small‐scale magnetic structure adjacent to a reconnecting current sheet at the dayside magnetopause. While MMS crosses the current sheet, it observes signatures of an electron diffusion region (EDR), including crescent shaped electron velocity distribution functions. Right after the EDR crossing, all spacecraft encounter an electron‐scale magnetic structure that can roughly be divided into two parts: a force‐free flux rope‐like part and a nonforce‐free magnetic enhancement. Within the leading force‐free part of the structure, the magnetic field component normal to the current sheet exhibits a bipolar signature, suggesting that the structure is flux rope‐like. In the trailing edge of the bipolar signature, three spacecraft observe a magnetic enhancement that has an amplitude almost twice the ambient magnetic field. The magnetic peak adjacent to an EDR can be associated with an electron vortex, where the perpendicular current is carried by E×B drifting electrons. The structure is advected tailward along the magnetopause while in the plasma frame, it propagates upstream suggesting that this reconnection event is highly three‐dimensional. Fluctuations in the plasma density and magnetic field and large peaks in the parallel electric field observed on the magnetospheric side of the EDR suggest that the current sheet is corrugated due to an electromagnetic drift instability. This or another instability of a thin reconnecting current sheet (e.g., tearing) is a likely cause of the formation of the observed magnetic structure.

Magnetic Reconnection in Three Dimensions: Modeling and Analysis of Electromagnetic Drift Waves in the Adjacent Current Sheet

AbstractWe present a model of electromagnetic drift waves in the current sheet adjacent to magnetic reconnection at the subsolar magnetopause. These drift waves are potentially important in governing 3‐D structure of subsolar magnetic reconnection and in generating turbulence. The drift waves propagate nearly parallel to the X line and are confined to a thin current sheet. The scale size normal to the current sheet is significantly less than the ion gyroradius and can be less than or on the order of the wavelength. The waves also have a limited extent along the magnetic field (B), making them a three‐dimensional eigenmode structure. In the current sheet, the background magnitudes of B and plasma density change significantly, calling for a treatment that incorporates an inhomogeneous plasma environment. Using detailed examination of Magnetospheric Multiscale observations, we find that the waves are best represented by series of electron vortices, superimposed on a primary electron drift, that propagate along the current sheet (parallel to the X line). The waves displace or corrugate the current sheet, which also potentially displaces the electron diffusion region. The model is based on fluid behavior of electrons, but ion motion must be treated kinetically. The strong electron drift along the X line is likely responsible for wave growth, similar to a lower hybrid drift instability. Contrary to a classical lower hybrid drift instability, however, the strong changes in the background B and no, the normal confinement to the current sheet, and the confinement along B are critical to the wave description.

Hybrid Indoor Localization Using IMU Sensors and Smartphone Camera.

Smartphone camera or inertial measurement unit (IMU) sensor-based systems can be independently used to provide accurate indoor positioning results. However, the accuracy of an IMU-based localization system depends on the magnitude of sensor errors that are caused by external electromagnetic noise or sensor drifts. Smartphone camera based positioning systems depend on the experimental floor map and the camera poses. The challenge in smartphone camera-based localization is that accuracy depends on the rapidness of changes in the user’s direction. In order to minimize the positioning errors in both the smartphone camera and IMU-based localization systems, we propose hybrid systems that combine both the camera-based and IMU sensor-based approaches for indoor localization. In this paper, an indoor experiment scenario is designed to analyse the performance of the IMU-based localization system, smartphone camera-based localization system and the proposed hybrid indoor localization system. The experiment results demonstrate the effectiveness of the proposed hybrid system and the results show that the proposed hybrid system exhibits significant position accuracy when compared to the IMU and smartphone camera-based localization systems. The performance of the proposed hybrid system is analysed in terms of average localization error and probability distributions of localization errors. The experiment results show that the proposed oriented fast rotated binary robust independent elementary features (BRIEF)-simultaneous localization and mapping (ORB-SLAM) with the IMU sensor hybrid system shows a mean localization error of 0.1398 m and the proposed simultaneous localization and mapping by fusion of keypoints and squared planar markers (UcoSLAM) with IMU sensor-based hybrid system has a 0.0690 m mean localization error and are compared with the individual localization systems in terms of mean error, maximum error, minimum error and standard deviation of error.

Intrinsic current driven by electromagnetic electron drift wave turbulence in the tokamak pedestal region

The local intrinsic parallel current density driven by electron drift wave (DW) turbulence including electromagnetic (EM) effects is analytically studied. The scalings of the ratios of intrinsic current density driven by residual turbulent flux and by a turbulent source to the bootstrap (BS) current density with electron density and temperature are predicted to be and respectively. Based on the typical parameters in the DIII-D pedestal region, the local intrinsic current density driven by both the residual turbulent flux and the turbulent source is negligible. However, despite the negligible turbulent source driven current, the residual turbulent flux driven local intrinsic current density by EM DW turbulence can reach about 66% of the BS current density for International Thermonuclear Experimental Reactor (ITER) pedestal parameters due to much lower collisionality in ITER than in DIII-D. Moreover, the contributions from adiabatic ES parts, non-adiabatic ES parts, and non-adiabatic EM parts of the plasma response to EM fluctuations are analyzed. It is found that there is a strong cancellation between the non-adiabatic ES response and the non-adiabatic EM response for the ITER pedestal case, and thus the kinetic stress contributed by the adiabatic ES response of parallel electron pressure dominates the intrinsic current drive. This is different from the ES electron DW case. Therefore, the EM effects on turbulence driven intrinsic current density should be carefully considered in the future reactor with a high ratio of electron pressure to the magnetic pressure and steep pressure profile.

Tidal and planetary waves in the lower thermosphere and ionosphere simulated with the EAGLE model for January 2009 sudden stratospheric warming conditions

This paper presents the analysis of planetary waves and tidal variability during January 2009 in the mesosphere, thermosphere, and ionosphere simulated with two versions of the EAGLE model. It is shown that sudden stratospheric warming (SSW) occurred in January 2009 leads to an increase in the planetary and tidal wave activity in the lower thermosphere. The features of the solar-migrating and non-migrating components of tidal variations in the thermosphere, ionosphere, and electric fields are considered. The reproduction of the vertical electromagnetic drift during the SSW period over the Jicamarca station is explained by a significant increase in the diurnal and semi-diurnal tidal activity.