Component Of Magnetic Field Research Articles

Key Signatures of Prominence Materials and Category of Cold Materials Identified by Random Forest Classifier

The origin of cold materials identified by different criteria is unclear. They are highly suspected to be erupted prominences. However, some cold materials defined by charge depletion exist in both quiet solar wind and interplanetary coronal mass ejections (ICMEs). Recently, solar observations show failed prominence eruption in coronal mass ejections (CMEs) that the prominence sometimes did not propagate into interplanetary space. This work uses Random Forest Classifier (RFC), which is an interpretable supervised machine-learning algorithm to study the distinct signatures of prominence cold materials (PCs) compared to quiet solar wind (QSW) and ICMEs excluding cold materials (ICMEEs). Twelve physical features measured by ACE at 1 au and the monthly averaged sunspot number are used in this study. The measurements from ACE are proton moments, magnetic field component B z , He/H, He/O, Fe/O, mean charge of oxygen and carbon, C6+/C5, C6+/C4+, and O7+/O6+. According to the returned weights from RFC that are checked by support vector machine classifier, the most important in situ signatures of PCs are obtained. Next, the trained RFC is used to check the category of the cold materials not related to CME observations. The results show that most segments of the cold materials are from prominences, but four of them are possibly from ICMEEs; another one segment is possibly from QSW. The most distinct signatures of PCs are lower (C6+/C5+)/(O7+/O6+), proton temperature, and He/O. Considering the obvious overlaps on key physical features between QSW, ICMEEs, and PCs, the multifeature classifier shows an advantage in identifying them than solid criteria.

Effect of strong geomagnetic storms and their association with solar wind plasma temperature and IMF during solar cycles 23 and 24.

Strong interaction of CMEs with Earth’s environment causes serious space weather effect through the coupled magnetosphere system. A geomagnetic storm is a global disruption of the earth’s magnetic field, and usually occurs in response to abnormal conditions in the IMF and solar wind. In this paper we present the consequences on interplanetary causes of strong geomagnetic storms (Dst ≤ -200nT), that occurred during solar cycle 23 and 24. It was found that the positive correlation with correlation coefficient (0.46) between the magnitude of strong geomagnetic storm and magnitude of solar wind plasma temperature, (0.54) between the magnitude of strong geomagnetic storm and magnitude of solar wind plasma velocity, (.58) between the magnitude of strong geomagnetic storm and magnitude of southward component of interplanetary magnetic field (IMF Bz) and (0.54) between strong geomagnetic storm and magnitude of interplanetary magnetic field (IMF Btotal).The correlation between magnitude of strong geomagnetic storm and magnitude of interplanetary magnetic field (with positive correlation coefficient 0.58) is higher, as compared with magnitude of strong geomagnetic storm and magnitude of solar wind plasma temperature (0.46). It has been verified that strong geomagnetic storm intensity is correlated well with the interplanetary magnetic field IMF (Btotal and Bz) better than with its solar parameters.

New Resonant Probes With High Detection Sensitivity and Measurement Characteristic of Two Orthogonal Magnetic-Field Components

New Resonant Probes With High Detection Sensitivity and Measurement Characteristic of Two Orthogonal Magnetic-Field Components

Possibilities of on-board gravimetric and hydromagnetic survey in solving engineering-geological problems on the shelf

This article shows the possibilities of using on-board gravimetry and hydromagnetometry in combination with high-resolution seismic surveys in the framework of site surveys on the Arctic shelf. Geotechnical surveys were carried out in the southern part of the Kara Sea shelf on a study area of 25 km2 in order to identify potentially hazardous areas for setting up a floating drilling rig. The studies were carried out using a regular network of observations, consisting of 51 line and 26 secant profiles. The length of each profile is 5 km. Gravimetric research were carried out with the Chekan-AM marine on-board gravimeter in conjunction with magnetometric research using SeaSPY 2 towed marine magnetometers. The depth of research when performing engineering and geological surveys using the presented set of methods is the first 100 meters, up to 1 km. In this case, objects and phenomena of both technogenic and geological nature can represent a potential hazard. As the experience of carrying out this type of work in the south of the Arctic shelf shows, paleoincisions and paleovalleys are common hazards of the geological nature of the region under study. These structures are traditionally filled with weakly consolidated, often gas-saturated, sediments with inclusions of coarse-grained material. Paleoincisions are clearly manifested in the high-frequency component of the magnetic field, and the local component of the anomalous magnetic field was calculated to reveal them. As a result of a complex interpretation of gravity field anomalies and magnetic survey data, a curved linear zone was localized, crossing the entire study area. The identified anomalous zone is confined to the boundaries of the paleoincision, which was originally discovered according to seismoacoustic studies. Based on the results of gravity surveys, an area of negative anomalies was identified in the eastern part of the study area. According to the materials of seismoacoustic in this zone, paleocuts of a complex spatial and deep configuration are traced. It is noteworthy that these structures are not manifested in a magnetic field. Based on the obtained values of the gravitational field and seismoacoustic data, a seismic-density section of meridional strike was constructed across the entire area. As a result of 2D density modeling, the densities for the undercut paleoincision were selected and two deconsolidations were found at a depth of 200 meters. One of the model “artifacts” does not appear according to seismoacoustic studies and hydromagnetometry. The detected areas of decompaction can be caused by the gas saturation of the sedimentary strata and must be taken into account when setting up a floating drilling platform. The interpretation of the anomalous gravitational field in the specified complex of geophysical methods with a priori geological information makes it possible to predict the density structure of the studied rock mass and gives recommendations for further research.

NUMERICAL MODELLING OF ELECTROMAGNETIC WAVE SCATTERING ON GRATINGS WITH ONE-DIMENSIONAL QUASI-FRACTAL PERIOD STRUCTURE

Numerical modelling of the properties of E-polarised and H-polarised waves scattered on periodic screened quasi-fractal gratings is carried out. The location of the band system at each period is determined by the principle of constructing a generalized symmetric Cantor set at a certain step of the algorithm. A mathematical model of the problems based on systems of boundary singular integral equations of the first kind was used in the study. These systems of equations were obtained using the method of parametric representations of singular and hypersingular integral operators. The systems of singular integral equations were solved numerically using the computational schemes of the method of discrete singularities. The solutions of these equations are used to obtain the main characteristics of the electric and magnetic fields. This experiment proved the possibility of using the MDS computational scheme to analyse systems containing 8 – 16 bands at different distances from each other. Graphs of the dependence of harmonic amplitudes on the wavenumber, point plots of absolute values of all non-zero harmonics at resonant wavenumber values, and maps of electric and magnetic field components in the region above the grating were obtained. It is confirmed that the overall field structure in the case of normal incidence is significantly influenced by all harmonics with absolute numbers from 0 to 50. The harmonics had a large number of resonances that were observed at different values of the wavenumber. This led to a complex structure of the isolines of absolute values of the scattered electric and magnetic field amplitudes in the region above the structure, and a significant difference in amplitude values with small changes in coordinates. In the future, it is planned to carry out computer simulations for imperfectly conducting structures and compare the results with the numerical results for the ideal case considered in this paper. The proposed structure may be of interest for the design of multimode broadband antennas.

Joint Effects of Heat Source and Magnetic Field on Unsteady Chemically Reacting Fluid Flow Towards A Vertically Inclined Plate in Addition of Cu-Nanoparticles

The primary goal of this evaluation task is to research the mathematical analysis for unstable, free convective incompressible viscous heat also mass transfer fluid movement across an inclined a plate that is vertically positioned in the occurrence of copper nanoparticles, Magnetism, thermal generator & chemical reaction in porous media. For this investigation, we assumed the effects of Cu-nanoparticles and Angle of inclination effects in the governing equations. Additionally, the effects of fluctuating temperature & concentration are studied. We established a set of basic equations for this fluid flow and translated nonlinear partial difference equations into linear incomplete comparisons, which were then answered using the implicit limited alteration technique. The impacts of several engineering fluid variables on flow variables such as velocity, temperature, & concentration profiles were explored in this research study via the use of graphs to show the findings. Along with the other findings, the mathematical standards of skin friction, heat transmission rate, & mass transmission constants are calculated and reported in tabular form. Finally, and perhaps most importantly, the mathematical consequences of the code validation programme are related to previously publish analytical results. In the instance of pure and nanofluids, the velocity profiles are shown to increase with rising values of the Heat transfer using the Grashof number, the mass movement Grashof number, the parameter for permeability, and the passage of time Increases in magnetic field component, the Schmidt number and the Prandtl number, the parameter for the heat source, the component of the chemical reaction, and the degree of inclination all result in a drop in the velocity profiles. With respect to temperature profiles, they have been on the rise with passing time, in contrast to the Prandtl number and the heat source parameter, for which the opposite trend has been seen. We discovered that the temperature and velocity profiles are both steeper for nanofluids than for pure fluids when the parameters are increased. The concentration profiles rise with increasing times, but the opposite is true for the Schmidt number. Moreover, increasing Chemical reaction parameter values result in decreasing profiles of concentrations.

The role of magnetic fields in the formation of the filamentary infrared dark cloud G11.11–0.12

ABSTRACT We report on the near-infrared polarimetric observations of G11.11–0.12 (hereafter G11) obtained with SIRPOL on the 1.4 m IRSF telescope. The starlight polarisation of the background stars reveals the on-sky component of magnetic fields in G11, and these are consistent with the field orientation observed from polarised dust emission at $850\, \mu$m. The magnetic fields in G11 are perpendicular to the filament, and are independent of the filament’s orientation relative to the Galactic plane. The field strength in the envelope of G11 is in the range $50-100\, \mu$G, derived from two methods. The analyses of the magnetic fields and gas velocity dispersion indicate that the envelope of G11 is supersonic but sub-Alfvénic. The critical mass-to-flux ratio in the envelope of G11 is close to 1 and increases to ≳ 1 on the spine of G11. The relative weights on the importance of magnetic fields, turbulence and gravity indicate that gravity dominates the dynamical state of G11, but with significant contribution from magnetic fields. The field strength, |B|, increases slower than the gas density, n, from the envelope to the spine of G11, characterized by |B|∝n0.3. The observed strength and orientation of magnetic fields in G11 imply that supersonic and sub-Alfvénic gas flow is channelled by the strong magnetic fields and is assembled into filaments perpendicular to the magnetic fields. The formation of low-mass stars is enhanced in the filaments with high column density, in agreement with the excess of low-mass protostars detected in the densest regions of G11.

Antiferromagnetic spin-3/2 Heisenberg model with the effects of Dzyaloshinskii–Moriya interaction

The antiferromagnetic (AFM) spin-3/2 Heisenberg model is explored by using a mean-field approach (MFA) with the inclusion of spin operators for a square lattice. The considered Hamiltonian consists of the bilinear exchange interaction [Formula: see text] and Dzyaloshinskii–Moriya interaction (DMI) [Formula: see text] parameters between the nearest-neighbor (NN) spins along the z- and y-axes and external magnetic field components [Formula: see text] and [Formula: see text] acting along the x- and z-axes, respectively. After obtaining the mathematical formulation of the magnetization components along the x- and z-directions in the MFA, their thermal changes are inspected to obtain the phase diagrams on the ([Formula: see text], T) and (H, T) planes for the given values of [Formula: see text] and [Formula: see text], respectively, with [Formula: see text] which leads to AFM interactions. It is found that the model not only presents the AFM and ferromagnetic (FM) phases but also the random (R) phase regions created by the existence of [Formula: see text] interaction. These three phases are observed to coexist for the appropriate values of given system parameters. The phase lines exhibit reentrant behavior when only the FM and R phases are present.

Reconciling the magnetic field in central disc galaxies with the dynamical mass using the cosmological simulations

ABSTRACT The Universe is pervaded by magnetic fields in different scales, although for simplicity, they are ignored in most cosmological simulations. In this paper, we use the TNG50, which is a large cosmological galaxy formation simulation that incorporates magnetic fields with an unprecedented resolution. We study the correlation of the magnetic field with various galaxy properties such as the total, stellar, and gaseous mass, circular velocity, size, and star formation rate. We find a linear correlation between the average magnetic field pervading the disc of galaxies in relative isolation and their circular velocities. In addition, we observed that in this sample the average magnetic field in the disc is correlated with the total mass as $\overline{B}\sim M_{\mathrm{tot, R_{\star }}}^{0.2}$. We also find that the massive galaxies with active wind-driven black hole feedback, do not follow this trend, as their magnetic field is substantially affected by this feedback mode in the TNG50 simulation. We show that the correlation of the magnetic field with the star formation rate is a little weaker than the circular velocity. Moreover, we compare the magnetic field components of the above sample with a compiled observational sample of non-cluster non-interacting nearby galaxies. Similar to the observation, we find a coupling between the ordered magnetic field and the circular velocity of the flat part of the rotation curve in the simulation, although contrary to the observation, the ordered component is dominant in the simulation.

IMF Dependence of Midnight Bifurcation in the Thermospheric Wind at an Auroral Latitude Based on Nine Winter Measurements in Tromsø, Norway

AbstractA thermospheric wind data set from a Fabry‐Perot interferometer (630 nm) and the ion velocity from a Dynasonde in Tromsø, Norway, was analyzed for nine winter seasons to study the dynamics of the thermosphere and F‐region ionosphere at an auroral latitude. This study focused on bifurcation in the zonal component of the neutral wind and ion velocity at midnight and its dependence on the Y component of the interplanetary magnetic field (IMF). Ionospheric plasma convection patterns are evidently imprinted on the thermospheric wind variations as aspects of the westward and eastward accelerations at dusk and late morning, respectively. The zonal wind bifurcates immediately before midnight for IMF By < 0, but for By > 0, it inverts gradually into the postmidnight sector. Neutral wind streams, originating from higher latitudes, may result in the dependence because of anti‐sunward plasma flow distorted in the polar cap.

A CMOS Hall Sensors Array With Integrated Readout Circuit Resilient to Local Magnetic Interference From Current-Carrying Traces

This paper proposes a CMOS Hall sensors array with readout circuitry to counteract the magnetic interference from nearby conductors carrying high currents. The 3×3 Hall sensors array with current-spinning collects the spatial magnetic field information in a time-interleaved manner while the readout circuitry, formed by a capacitively-coupled instrumentation amplifier (CCIA) with T-capacitor feedback network, amplifies the transduced signals for subsequent processing. The calibration mechanism analyzes the magnetic field distribution on the array and separates the magnetic field component due to the environment and local perturbation from adjacent traces, enabling accurate detection of the environmental magnetic field. Prototyped in a 0.35-μm CMOS process, the Hall sensors array and readout circuit occupy an area of 2.2 × 2.2 mm2 and consume 3.5 mA of current under a 3.3-V supply. The hall sensors achieve an average sensitivity of 100 V/(A·T). The input-referred noise of the entire circuit is 0.128 μT/√Hz. With the interference cancellation scheme, the error in the magnetic field readings caused by a conductor 5 mm from the center of the chip carrying 3 A of current reduced from 120 to 5 μT, corresponding to a 24× improvement. Overall, the average error of the captured magnetic field after calibration reaches 0.9%.

Geomagnetic storms in relation to interplanetary magnetic fields and southward component of interplanetary magnetic field during solar cycle 24

Geomagnetic storms in relation to interplanetary magnetic fields and southward component of interplanetary magnetic field during solar cycle 24

Reflection and refraction of higher-order Hermite-Gaussian beams: a vector wave analysis.

Hermite-Gaussian beams, as a typical kind of higher-order mode laser beams, have attracted intensive attention because of their interesting properties and potential applications. In this paper, a full vector wave analysis of the higher-order Hermite-Gaussian beams upon reflection and refraction is reported. The explicit analytical expressions for the electric and magnetic field components of the reflected and refracted Hermite-Gaussian beams are derived with the aid of angular spectrum representation and vector potential in the Lorenz gauge. Based on the derived analytical expressions, local field distributions of higher-order Hermite-Gaussian beams reflection and refraction at a plane interface between air and BK7 glass are displayed and analyzed.

GEOMAGNETIC EFFECT OF THE EARTHQUAKES <i>M</i>w = 7.5–7.8 IN TURKEY ON FEBRUARY 6, 2023

We study the response in geomagnetic field variations caused by a series of earthquakes with magnitudes Mw = 7.5–7.8 in Turkey on 6 February 2023. Initial data represent high-precision observations of the geomagnetic field with a 1-s sampling rate recorded at magnetic observatories of Russia and neighboring countries from middle to high latitudes. The paper analyzes the morphology of the geomagnetic signal, its amplitude-frequency characteristics, pulses in the rate of change and delays of the geomagnetic field response to earthquakes with magnitudes Mw = 7–8 depending on the distance to the source. The results suggest that the geomagnetic effect is best detected in the rate of change recordings, reaching anomalous amplitudes of 10 nT/s. The signal delay is from 221 to 592 s depending on the magnetic field component and the distance to the epicenter, which for the selected observatories falls in the range from 765 to 2650 km.

Jets and Mirror Mode Waves in Earth's Magnetosheath.

Magnetosheath jets are localized plasma structures with high dynamic pressure which are frequently observed downstream of the Earth's bow shock. In this work we analyze Magnetospheric MultiScale magnetic field and plasma data and show that jets can be found in the quasi-perpendicular magnetosheath in regions permeated by Mirror mode waves (MMWs). We show that structures identified as jets by their enhanced dynamic pressure can have very different internal structure, with variable signatures in magnetic field magnitude and components, velocity, and density and can be associated to ion distribution functions of various types. This suggests that jets observed in the quasi-perpendicular magnetosheath are generated by different mechanisms. We find that jets can be related to traveling foreshocks, flux transfer events, and some have MMWs inside them. Our results suggest that some jets have a local source and their formation does not depend on upstream structures. We find that different types of ion distributions can exist inside the jets, while in some cases anisotropic distributions are present, in others counterstreaming distributions exist. We also show that for jets with MMWs inside them, ion distributions can be modulated. This highlights the importance of using ion distributions to identify and classify different types of jets.

A Model of High Latitude Ionospheric Convection Derived From SuperDARN EOF Model Data

AbstractForecasting of the effects of thermospheric drag on satellites will be improved significantly with better modeling of space weather effects on the high‐latitude ionosphere, in particular the Joule heating arising from electric field variability. We use a regression analysis to build a model of the ionospheric convection drift velocity which is driven by relatively few solar and solar wind variables. The model is developed using a solar cycle's worth (1997–2008 inclusive) of 5‐min resolution Empirical Orthogonal Function (EOF) patterns derived from Super Dual Auroral Radar Network (SuperDARN) line‐of‐sight observations of the convection velocity across the high‐latitude northern hemisphere ionosphere. At key stages of development of the model, we use the percentage of explained variance P to see how well the model reproduces the EOF data. The final model is driven by four variables: (a) the interplanetary magnetic field component By, (b) the solar wind coupling parameter epsilon ε, (c) a trigonometric function of day‐of‐year, and (d) the monthly F10.7 index. The model can reproduce the EOF velocities with a characteristic P = 0.7. The model and EOF data compare best around the solar maximum of 2001. is lower around solar minimum, due to occasional limitations in the geographical and temporal coverage of the SuperDARN measurements. This may indicate the need to modify our model around the minimum of the solar cycle. Our model has the potential to be used to forecast the ionospheric electric field using the real‐time solar wind data available from spacecraft located upstream of the Earth.

Kinetic Equilibrium of Two-dimensional Force-free Current Sheets

Force-free current sheets are local plasma structures with field-aligned electric currents and approximately uniform plasma pressures. Such structures, widely found throughout the heliosphere, are sites for plasma instabilities and magnetic reconnection, the growth rate of which is controlled by the structure’s current-sheet configuration. Despite the fact that many kinetic equilibrium models have been developed for one-dimensional force-free current sheets, their two-dimensional (2D) counterparts, which have a magnetic field component normal to the current sheets, have not received sufficient attention to date. Here, using particle-in-cell simulations, we search for such 2D force-free current sheets through relaxation from an initial, magnetohydrodynamic equilibrium. Kinetic equilibria are established toward the end of our simulations, thus demonstrating the existence of kinetic force-free current sheets. Although the system currents in the late equilibrium state remain field aligned as in the initial configuration, the velocity distribution functions of both ions and electrons systematically evolve from their initial drifting Maxwellians to their final time-stationary Vlasov state. The existence of 2D force-free current sheets at kinetic equilibrium necessitates future work in discovering additional integrals of motion of the system, constructing the kinetic distribution functions, and eventually investigating their stability properties.

Variations in cosmic ray cutoff rigidities during the March 8–11, 2012 magnetic storm (CAWSES II period)

The geomagnetic cutoff rigidity of cosmic rays (CRs) is the main factor regulating the arrival of CR particles at a given point on Earth's surface or inside the magnetosphere. To study the relationship between cutoffs and near-Earth space parameters, we have selected the strongest magnetic storm that occurred on March 8–11, 2012 during the CAWSES-II interval, recommended by SCOSTEP for detailed studies of solar-terrestrial relations. We have found the geomagnetic cutoffs by two methods: 1) by trajectory calculations in the magnetic field of the perturbed magnetosphere according to the Ts01 model and 2) by the spectrographic global survey method according to the data from the world network of neutron monitors. The largest drop in the cutoffs (−1.1 GV) obtained by the latter method was observed during the recovery phase of the storm. Apparently, this is due to the influence of the supersubstorms that occurred at that time. The analysis has shown that the closest connection of variations in the cutoffs can be traced with the geomagnetic activity index Dst, which indicates the determining contribution of the ring current to the transport of CRs. In addition, we have found a significant connection with the electromagnetic field parameters (with the Bz component of the interplanetary magnetic field and the azimuthal component of the electric field Ey). The dynamic solar wind parameters practically do not control variations in CR geomagnetic cutoff rigidities.

Изменения жесткостей обрезания космических лучей во время бури 8–11 марта 2012 г в период CAWSES-II

The geomagnetic cutoff rigidity of cosmic rays (CRs) is the main factor regulating the arrival of CR particles at a given point on Earth's surface or inside the magnetosphere. To study the relationship between cutoffs and near-Earth space parameters, we have selected the strongest magnetic storm that occurred on March 8–11, 2012 during the CAWSES-II interval, recommended by SCOSTEP for detailed studies of solar-terrestrial relations. We have found the geomagnetic cutoffs by two methods: 1) by trajectory calculations in the magnetic field of the perturbed magnetosphere according to the Ts01 model and 2) by the spectrographic global survey method according to the data from the world network of neutron monitors. The largest drop in the cutoffs (−1.1 GV) obtained by the latter method was observed during the recovery phase of the storm. Apparently, this is due to the influence of the supersubstorms that occurred at that time. The analysis has shown that the closest connection of variations in the cutoffs can be traced with the geomagnetic activity index Dst, which indicates the determining contribution of the ring current to the transport of CRs. In addition, we have found a significant connection with the electromagnetic field parameters (with the Bz component of the interplanetary magnetic field and the azimuthal component of the electric field Ey). The dynamic solar wind parameters practically do not control variations in CR geomagnetic cutoff rigidities.

Numerical simulations of polarisation in gamma-ray burst afterglows

Abstract We compute the linear polarisation during the afterglow phase of gamma-ray bursts, for both on-axis and off-axis observers. We use numerical simulations of the deceleration of a relativistic jet, and compute the polarisation by post-processing the results of the numerical simulations. In our simulations, we consider a magnetic field that is chaotic in the plane of the shock, in addition to a magnetic field component that is parallel to the shock velocity. While the linear polarisation computed for on-axis observers is consistent with previous analytical estimates, we found that lateral expansion, which is accurately handled in our simulations, plays a crucial role in determining the linear polarisation for off-axis observers. Our results show that the off-axis linear polarisation, as seen by off-axis observers, exhibits a single peak, in contrast to the two peaks inferred by previous analytical studies. The maximum polarisation degree is 40 per cent at an observing angle θobs = 0.4 rad, and it decreases as the observing angle increases, which is opposite to what predicted by analytical models, where polarisation increases with larger observing angles. From the upper limit of 12 per cent in the linear polarisation obtained at 244 days for the GRB 170817A, we also infer an anisotropy factor of B∥/B⊥ = 0.5 − 0.9, consistent with the post-shock magnetic field being amplified by turbulence.