Strong Magnetic Field Research Articles

Comparison of magnetized thick disks around black holes and boson stars

Boson stars are considered as promising candidates for black hole mimickers. Similar to other compact objects they can form accretion disks around them. The properties of these disks could possibly distinguish them from other compact objects like black holes in future observations. Retrograde thick disks around boson stars and the influence of strong magnetic fields on them were already studied and it was shown that they can harbor very distinct features compared to black hole disks. However, the case of prograde thick disks is mostly unexplored, since they may appear much more similar to black hole disks. In this work we will investigate similarities and differences regarding prograde thick disks around non-selfinteracting rotating boson stars and rotating black holes. We assume thereby a polytropic equation of state and a constant specific angular momentum distribution of the disks. We classify the various conceivable boson star and black hole solutions by a dimensionless spin parameter a and compare their corresponding disk solutions. The influence of toroidal magnetic fields on the disks is analyzed by selected disk properties, as the rest-mass density distribution and the Bernoulli parameter. Disk solutions are characterized by their degree of magnetization represented by the magnetization parameter βmc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta _{mc}$$\\end{document}. We found that strong magnetic fields can strengthen the differences of disk solutions or oppositely even lead to a correlation in disk properties, depending on the spin parameter of the boson star and black hole solutions. We identify the vertical thickness of the boson star disks as the main differentiating factor, since for most solutions the vertical density distribution is far more outreaching for boson star disks compared to black hole disks.

Instability of Electroweak Homogeneous Vacua in Strong Magnetic Fields

AbstractWe consider the classical vacua of the Weinberg–Salam (WS) model of electroweak forces. These are no-particle, static solutions to the WS equations minimizing the WS energy locally. We study the WS vacuum solutions exhibiting a non-vanishing average magnetic field of strength b and prove that (i) there is a magnetic field threshold $$b_*$$ b ∗ such that for $$b<b_*$$ b < b ∗ , the vacua are translationally invariant (and the magnetic field is constant), while, for $$b>b_*$$ b > b ∗ , they are not, (ii) for $$b>b_*$$ b > b ∗ , there are non-translationally invariant solutions with lower energy per unit volume and with the discrete translational symmetry of a 2D lattice in the plane transversal to b, and (iii) the lattice minimizing the energy per unit volume approaches the hexagonal one as the magnetic field strength approaches the threshold $$b_*$$ b ∗ . In the absence of particles, the Weinberg–Salam model reduces to the Yang–Mills–Higgs (YMH) equations for the gauge group U(2). Thus, our results can be rephrased as the corresponding statements about the U(2)-YMH equations.

Generating spokes in direct current magnetron sputtering discharges by an azimuthal strong-to-weak magnetic field strength transition

Abstract Spokes are regions of enhanced ionization in magnetron sputtering discharges that are interesting because of their role for magnetron operation and their potential effect on deposition processes. Here, we show that spokes can intentionally be generated by introducing a strong-to-weak magnetic field strength transition along the racetrack. Spokes are triggered at the transition point from an accelerating electron drift when weakening the magnetic field strength. The spokes are then propagating against the electron drift into the strong magnetic field strength section of the racetrack. At the weak-to-strong magnetic field transition, we observe the inverse effect. The electron drift is decelerated at this point, creating a region of enhanced optical emission. From rectangular racetracks this is known as the cross-corner effect. Here, we show that a corner is not necessary for observing that effect. Pronounced spokes at low working gas pressure of 0.2 Pa exhibit a substructure that could be caused by the diocotron instability previously predicted by computer simulations.

Magnetospheric flows in X-ray pulsars – I. Instability at super-Eddington regime of accretion

ABSTRACT Within the magnetospheric radius, the geometry of accretion flow in X-ray pulsars is shaped by a strong magnetic field of a neutron star. Starting at the magnetospheric radius, accretion flow follows field lines and reaches the stellar surface in small regions located close to the magnetic poles of a star. At low mass accretion rates, the dynamics of the flow is determined by gravitational attraction and rotation of the magnetosphere due to the centrifugal force. At the luminosity range close to the Eddington limit and above it, the flow is additionally affected by the radiative force. We construct a model simulating accretion flow dynamics over the magnetosphere, assuming that the flow strictly follows field lines and is affected by gravity, radiative, and centrifugal forces only. The magnetic field of a neutron star is taken to be dominated by the dipole component of arbitrary inclination with respect to the accretion disc plane. We show that accretion flow becomes unstable at high mass accretion rates and tends to fluctuate quasi-periodically with a typical period comparable to the free-fall time from the inner disc radius. The inclination of a magnetic dipole with respect to the disc plane and strong anisotropy of X-ray radiation stabilize the mass accretion rate at the poles of a star, but the surface density of material covering the magnetosphere fluctuates even in this case.

Measurement of Rubidium Vapor Density Based on Spin‐Exchange Rate

AbstractAn efficient method is proposed for quantifying rubidium vapor density by analyzing the spin‐exchange rate between alkali metals. This method effectively addresses two primary challenges in measuring alkali vapor density. First, it overcomes the limitation of absorption spectroscopy to measure vapor density under optically thick conditions, typically restricted to temperature higher than 420K, equivalent to alkali vapor density exceeding . Second, it mitigates the risk of disrupting shielding functionality due to the application of a strong magnetic field, often in the range of several tens of Gauss or higher, when employing the Faraday rotation for vapor‐density measurement. The spin‐exchange rate between atoms, inherently related to the vapor density, is evident in the electron‐paramagnetic‐resonance spectrum of spin‐polarized , thereby providing a possibility for measuring alkali vapor density. To eliminate overlap between two Lorentzian curves resulting from two decomposed components of an oscillating field, a small rotating magnetic field with identical amplitude and frequency but a 90‐degree phase shift along both the x and y axes is applied. This method is successfully employed to measure vapor density in the temperature range of 373–433 K, with the measured outcomes closely matching the saturation vapor curve.

The escape of fast radio burst emission from magnetars

ABSTRACT We reconsider the escape of high-brightness coherent emission of fast radio bursts (FRBs) from magnetars’ magnetospheres, and conclude that there are numerous ways for the powerful FRB pulse to avoid non-linear absorption. Sufficiently strong surface magnetic fields, $\ge 10{{\ \rm per\ cent}}$ of the quantum field, limit the waves’ non-linearity to moderate values. For weaker fields, the electric field experienced by a particle is limited by a combined ponderomotive and parallel-adiabatic forward acceleration of charges by the incoming FRB pulse along the magnetic field lines newly opened during FRB/coronal mass ejection. As a result, particles surf the weaker front part of the pulse, experiencing low radiative losses, and are cleared from the magnetosphere for the bulk of the pulse to propagate. We also find that initial mildly relativistic radial plasma flow further reduces losses.

Tracking of a Magnetically Navigated Millirobot With a Magnetic-Field Camera

Significant progress has been made in the development of magnetic micromanipulation for minimally invasive surgery. The development of systems to localize millimeter-sized robots during magnetic manipulation without line-of-sight detection remains, however, a challenging task. In this study, we focused on the development of a tracking system aiming to fill this gap. A robot which consists of a cylindrical magnet of 1 mm diameter is localized using a 2D array of 3D magnetoresistive sensors. The system, also called magnetic field camera, provides tracking of the robot with a refresh rate of 2 Hz. The developed tracking algorithm reaches a mean absolute error for the position and the orientation of, respectively 0.56 mm and 5.13° in 2D. This system can be added to existing magnetic manipulation systems allowing closed loop control of the navigation. The performances of the magnetic field camera are not affected by an exposure to strong magnetic fields. Exposures up to 3 T have been validated. Increasing the integrability of the magnetic field camera into magnetic manipulation systems. The presented tracking system makes it possible to target applications such as minimally invasive eye surgery or drug delivery. The high spatial and magnetic resolutions allow the tracking of magnetic particles, down to 200 μm diameter, when placed close to the surface. The system could also be suitable for the localization of small objects for 2D biomanipulation.

The search for new pathogenesis of cardiorenal syndrome: the effect of local Schumann resonance on the occurrence of episodes of kidney disease and myocardial infarction

Background. The pandemic of noncommunicable chronic diseases and the high prevalence of combined damage to the cardiovascular system and kidneys determine the relevance of continuing scientific research to solve these medical problems. Therefore, the aim of this study was to compare the influence of the Earth’s electromagnetic field on the occurrence of episodes of kidney disease and myocardial infarction in order to search for new pathogenetic components of cardiorenal syndrome and deepen fundamental knowledge. According to the Lithuanian magnetometer GCI003, a number of stu­dies in 2014–2018 found that changes in the Earth’s electromagnetic field may play an important role in the pathogenesis of cardiovascular diseases as well as their incidence. Since the functioning of the cardiovascular system and kidneys are closely connected through the metabolic processes of the cardiorenal metabolic axis, this study tested the hypothesis that changes in the Earth’s electromagnetic field may also affect the pathogenesis of kidney disease as the changes of local magnetic field have been shown to influence the functioning of the cardiovascular system. Materials and methods. This was a search retrospective study on the relationship between the influence of local Schumann resonances and the occurrence of hospitalizations in 1340 patients with kidney disease. It also examined the relationship between local Schumann resonances and heart attacks in patients admitted to the University Hospital of the Lithuanian University of Health Sciences (703 patients). Mean power of local magnetic field fluctuations in Lithuania was measured in pT2 s2 in five different frequency ranges, which overlaps the Schumann resonance and electroencephalogram’s frequency ranges: SDelta (0–3.5 Hz), STheta (3.5–7 Hz), SAlpha (7–15 Hz), SBeta (15–32 Hz), SGamma (32–66 Hz). The data of hospitalizations to the Nephrology Department of University Hospital and the dynamics of Schumann resonances were analyzed from January 1, 2021 to December 31, 2021. The data of hospitalizations for myocardial infarction to the Cardiology Department of University Hospital and the dynamics of Schumann resonances were studied from January 1, 2016 to December 31, 2016. Results. It was found that changes in the strength of the Earth’s local magnetic field in 2016 and 2021 were comparable and corresponded to the characteristic annual dynamics of the Earth’s local electromagnetic fields. This made it possible to conduct a comparative analysis of annual correlation graphs and establish general trends in the dynamics of indicators and graphical similarities. It confirmed the pre­sence of a general dependence of reactions to the external electromagnetic field of the Earth in female and male patients both with nephrological pathology and myocardial infarction. In nephrological patients of both sexes, all correlation coefficients in all ranges of Schumann resonances were positive. The only negative correlation coefficient P5 (SGamma) [32; 65] Hz (r = –0.069; p = 0.313) was in the female group. This fact as well as the presence of a significant dynamics of the correlation coefficient P5 (SGamma) [32; 65] Hz (r = 0.009; p = 0.475) in the male group indicate that higher magnetic field strength in this frequency range may be associated with a reduced incidence of kidney disease. We obtained data that a higher magnetic field intensity in the gamma range from 32 to 65 Hz as a pathogenetic component can contribute to the destabilization of the cardiovascular system, but at the same time it is associated with a positive effect on the state of nephrological pathology. Based on this, we can tentatively assume the opposite direction of the Earth’s electromagnetic field influence on the pathogenetic mechanisms of renal and cardiovascular diseases. This is clearly demonstrated by comparing the correlation coefficients between the incidence of kidney disease and the occurrence of myocardial infarction in men and women. The Earth’s stronger magnetic field in the gamma range contributes to an increase in the incidence of myocardial infarction, which is confirmed by the large number of patients during this period. Under these same conditions, a decrease in the incidence of kidney disease has been detected. This opposite direction is observed in both sexes. But in women the reaction is stronger, which is confirmed by a larger difference in correlation coefficients. Conclusions. 1. Changes in the Earth’s electromagnetic field are related to the functional state of the cardiovascular system and the condition of the kidneys. 2. It can be assumed that the effect of the Earth’s electromagnetic field on the pathogenetic mechanisms of kidney disease is in the opposite direction of that on the cardiovascular one. 3. Reliable gender differences in correlations between the influence of changes in the local Schumann resonance on the functional state of the cardiovascular system and kidneys were not found. 4. The connection of the Earth’s local geomagnetic field with kidney function may be another new unexplored pathogenetic mechanism in cardiorenal syndrome and noncommunicable chronic diseases.

Landau–Zener–Stückelberg–Majorana-like dynamics induced by tunneling of spin qubit states in a multiband two-state magnetic quantum wire

We investigate the transfer between spin quantum bit (qubit) states and study the Landau–Zener–Stückelberg–Majorana (LZSM)-like dynamics of tunneling spin qubits in a multiband two-state magnetic quantum wire. Indeed, within the framework of an optical parabolic potential in a three-dimensional (3D) heterostructure quantum wire and under the influence of an external time-varying magnetic field, a model for a multiband two-state magnetic quantum wire is developed. Here, the external magnetic field is used to coherently manipulate and control spin qubit states. By driving the system through an avoided crossing, we consider the associated effective quantum two-level system (TLS) related to the spin qubit states in each band, driving by an external coherent magnetic field in which the related Hamiltonian is Hermitian, and which generally paves a way to LZSM interferometry. Thus, we establish the analytical expressions of the energy eigenvalues in each band and derive the analytical solution of the dynamical evolution of the tunneling probabilities of the associated TLS. Accordingly, nonadiabatic and adiabatic tunneling probabilities (survival and transition) are calculated for each band of the multiband TLS. In this respect, the nonadiabatic and adiabatic dynamical evolutions of the tunneling probabilities of spin qubit populations in the first four bands, with band quantum numbers n = 0, 1, 2 and 3 are analyzed. As a result, depending on the amplitude strength of the driven magnetic field and the magnitude of the driving frequency, we report two striking nonadiabatic and adiabatic scenarios in each band for both the diabatic and adiabatic states. In this context, driving the two states of each band of the multiband TLS related to the spin qubit states through an avoided level crossing can result in nontrivial and incoherent dynamics at certain phases, resulting to apparent inaccurate probabilities, especially in the case of strong driven magnetic field and high driving frequency.

Three-dimensional flat Landau levels in an inhomogeneous acoustic crystal

When electrons moving in two dimensions (2D) are subjected to a strong uniform magnetic field, they form flat bands called Landau levels (LLs). LLs can also arise from pseudomagnetic fields (PMFs) induced by lattice distortions. In three-dimensional (3D) systems, there has been no experimental demonstration of LLs as a type of flat band thus far. Here, we report the experimental realization of a flat 3D LL in an acoustic crystal. Starting from a lattice whose bandstructure exhibits a nodal ring, we design an inhomogeneous distortion corresponding to a specific pseudomagnetic vector potential (PVP). This distortion causes the nodal ring states to break up into LLs, including a zeroth LL that is flat along all three directions. These findings suggest the possibility of using nodal ring materials to generate 3D flat bands, allowing access to strong interactions and other attractive physical regimes in 3D.

Observations of spiral and streamer on a candidate proto-brown dwarf

ABSTRACT Spirals and streamers are the hallmarks of mass accretion during the early stages of star formation. We present the first observations of a large-scale spiral and a streamer towards a very young brown dwarf candidate in its early formation stages. These observations show, for the first time, the influence of external environment that results in asymmetric mass accretion via feeding filaments on to a candidate proto-brown dwarf in the making. The impact of the streamer has produced emission in warm carbon-chain species close to the candidate proto-brown dwarf. Two contrasting scenarios, a pseudo-disc twisted by core rotation and the collision of dense cores, can both explain these structures. The former argues for the presence of a strong magnetic field in brown dwarf formation while the latter suggests that a minimal magnetic field allows large-scale spirals and clumps to form far from the candidate proto-brown dwarf.

Budget equations and astrophysical nonlinear mean-field dynamos

Abstract Solar, stellar and galactic large-scale magnetic fields are originated due to a combined action of non-uniform (differential) rotation and helical motions of plasma via mean-field dynamos. Usually, nonlinear mean-field dynamo theories take into account algebraic and dynamic quenching of alpha effect and algebraic quenching of turbulent magnetic diffusivity. However, the theories of the algebraic quenching do not take into account the effect of modification of the source of turbulence by the growing large-scale magnetic field. This phenomenon is due to the dissipation of the strong large-scale magnetic field resulting in an increase of the total turbulent energy. This effect has been studied using the budget equation for the total turbulent energy (which takes into account the feedback of the generated large-scale magnetic field on the background turbulence) for (i) a forced turbulence, (ii) a shear-produced turbulence and (iii) a convective turbulence. As the result of this effect, a nonlinear dynamo number decreases with increase of the large-scale magnetic field, so that that the mean-field αΩ, α2 and α2Ω dynamo instabilities are always saturated by the strong large-scale magnetic field.

An in-situ magnetising holder achieving 1.5 T in-plane field in 200 kV transmission electron microscope

A strong in-plane magnetic field is required for Lorentz transmission electron microscopy (LTEM) to observe the evolution of the magnetic domain structure of materials with high coercivity, particularly for research on rare-earth permanent magnets. However, the maximum field of the present in-situ magnetising holder applied in 200-kV or 300-kV TEM does not exceed 0.1 T. In this study, the reason for the low field was analysed, and the field strength was significantly elevated by reducing the field application area of the field generator. From finite element method calculations and experimental measurements, a 1.5 T in-plane field was achieved by our new holder in a 200-kV TEM, and images with good quality could still be obtained. Using the newly developed holder, the magnetisation process of hot-pressed NdFeB magnets was observed. The in-situ magnetising holder can be used in research on a wide variety of magnetic materials.

Thermomagnetic convection control strategies for electromagnetic devices immersed in a ferrofluid

This paper presents new control strategies for improving the thermomagnetic convection intensity in electromagnetic devices. The system consists of a winding prototype immersed in a ferrofluid solution based on magnetic nanoparticles. The whole system is exposed to an external magnetic field generated by an annular magnet placed against the tank. When possible, experimental results are compared with numerical ones obtained using the finite element method in a 2D-axisymmetric setting. The first control strategy consists of assessing the impact of Curie’s temperature on heat removal. Numerical calculations show that the maximum winding temperature decreases by 2.2°C with the use of magnetic nanoparticles with the lowest Curie temperature. Employing an auxiliary magnetic field may be another method for monitoring the thermomagnetic convection. The number of streamlines increases in the upper part of the tank due to the intensification of the magnetic force at the top of the winding. It is shown that magnetization, orientation, and location of the magnet play a crucial role in maximizing heat transfer inside the tank. The experiment shows a temperature decrease of 9 °C at the top of the winding if an external magnetic field is applied.

Surveys of clumps, cores, and condensations in Cygnus X. Temperature and nonthermal velocity dispersion revealed by VLA NH3 observations

The physical properties, evolution, and fragmentation of massive dense cores (MDCs 0.1 pc) are fundamental pieces in our understanding of high-mass star formation. We aim to characterize the temperature, velocity dispersion, and fragmentation of the MDCs in the giant molecular cloud and to investigate the stability and dynamics of these cores. We present the Karl G. Jansky Very Large Array (VLA) observations of the ($J,K$) = and inversion lines towards 35 MDCs in from which we calculated the temperature and velocity dispersion. We extracted 202 fragments ( 0.02 pc) from the moment-0 maps with the GAUSSCLUMPS algorithm. We analyzed the stability of the MDCs and their fragments through evaluating the corresponding kinetic, gravitational potential, and magnetic energies and the virial parameters. The MDCs in Cygnus X have a typical mean kinetic temperature of 20 K. Our virial analysis shows that many MDCs are in subvirialized states, indicating that the kinetic energy is insufficient to support these MDCs against their gravity. The calculated nonthermal velocity dispersions of most MDCs are at transonic to mildly supersonic levels, and the bulk motions make only a minor contribution to the velocity dispersion. Regarding the fragments, with 19 K, their nonthermal velocity dispersions are mostly trans-sonic to subsonic. Unless there is a strong magnetic field, most fragments are probably not in virialized states. We also find that most of the fragments are dynamically quiescent, while only a few are active due to star formation activity.

Squeeze film derivation of the porous curved annular plates with variable magnetic field, Rosensweig’s viscosity and slip velocity in the Shliomis model

PurposeThe present article aims to investigate the squeeze effects on hematite suspension-based curved annular plates with Rosensweig’s viscosity and Kozeny–Carman’s porous structure under the variable strong magnetic field and slip in the Shliomis model. The variable magnetic field is utilised to retain all magnetic elements within the model. The aforementioned mechanism would have the benefit of generating a maximal field at the system’s required active contact zone.Design/methodology/approachThe Kozeny–Carman globular sphere model is used for porous facing. Rosensweig’s extension of Einstein’s viscosity is taken into consideration to enhance the fluid’s viscosity, and Beavers and Joseph’s slip boundary conditions are employed to assess the slip effect.FindingsThe pressure and lifting force under squeezing are computed through modification of the Reynolds equation with the addition of Kozeny–Carman’s model-based porosity, Rosensweig’s viscosity, slip and varying magnetic field. The obtained results for the lifting force are very encouraging and have been compared with Einstein’s viscosity-based model.Originality/valueResearchers so far have carried out problems on lubrication of various sliders considering Einstein’s viscosity only, whereas in our problem, Rosensweig’s viscosity has been taken along with Kozeny–Carman’s porous structure model.

Thermal evolution and axion emission properties of strongly magnetized neutron stars

Emission properties of compact astrophysical objects such as Neutron stars (NSs) are associated with crucial astronomical observables. In the current work, we obtain the mass, pressure profiles of the non-rotating NSs using the modified Tolman Oppenheimer Volkoff (TOV) system of equations in the presence of intense magnetic field. We obtain the profiles by using a specific distance-dependent magnetic field in the modified TOV equations. We employ three different equations of states (EoS) to solve the TOV equations by assuming the core of NSs comprises a hadronic matter. Employing the above profiles, we determine the cooling rates of spherically symmetric NSs as a function of time with and without including the magnetic field using the NSCool code. We have also determined the cooling rates as a function of radius for three different NSs. Furthermore, we determine the luminosity of neutrinos, axions, and photons emitting from the NSs in the presence and absence of a magnetic field for an axion mass 16 meV and three different EoS. Our comparative study indicates that the cooling rate and luminosities of neutrinos, axions, and photons change significantly due to the impact of the strong magnetic field. We also find that due to the magnetic field, the axion mass bound increases slightly compared to without a magnetic field.

Impact of non-linear heat source and magnetic field on the Carreau nanofluid Marangoni convective flow – a numerical investigation

ABSTRACT A recent study examines the features of a dusty Carreau nanofluid over a flat surface with allowance for mixed convection that is not linear and heat radiation. It also examines how these factors affect fluid movement due to temperature differences (thermal Marangoni effect). The change in surface tension levels causes Marangoni convection, which finds applications in scientific areas like making crystals, keeping soap bubbles steady, drying thin wafers and dry silicon. Similarity transformations have been incorporated to create ODEs from PDEs. The complex non-dimensional differential equations are then solved using a numerical method called shooting method (with RKF-45 approach). For the momentum and heat distribution analysis, physical parameters are expressed in detail. The findings show that the Marangoni flow makes heat move quicker. In the same way, there is a decrease in the fluid’s velocity due to magnetic effects.

Finite element modeling of the rotational dynamics of a single magnetic particle in a strong magnetic field and liquid medium

We have performed a comparative computational study of magnetic particle alignment in a strong magnetic field and ambient viscous fluid using the first-principles Navier–Stokes equation as well as numerical modeling using the finite element method (FEM). FEM solution has been compared with the solution of the unsteady rotations of a magnetic particle in a viscous fluid during the alignment process described with nonlocal integro-differential equations (IDEs) for torque and angular velocity. The assumption of nonlocality comes from the history term of acceleration torque with a non-Basset kernel function, which has its origin in the presence of vortices in the flow of a particle fluid environment due to its unsteady rotation and ambient fluid inertia and friction. The flow vortices of the ambient fluid are explicitly shown in the solution of the FEM model. Moreover, the solution of the time evolution of the alignment angle and angular velocity for the FEM model are in good agreement with an IDE model which we have recently developed. The obtained results are justification for interchangeability of the FEM and IDE models, which may have important consequences for large-scale simulations of magnetic microparticles.

Hybrid Simulation of Magnetosheath Jet‐Driven Bow Waves

AbstractHigh‐speed jets (HSJs) are commonly observed in the Earth's magnetosheath. The HSJs can drive shock‐like bow waves when compressing the ambient plasma, which are important for the HSJ's evolution and the energization of charged particles. Here we present the first two‐dimensional hybrid simulation of the formation and evolution of jet‐driven bow waves. The simulated bow waves exhibit localized enhanced magnetic field and ion density, with their peaks separated by the order of ion inertial length. The bow waves are formed when a super‐magnetosonic HSJ encounters a magnetic structure with the magnetic field nearly perpendicular to the HSJ's velocity. The magnetic field structure acts as an obstacle to deflect and decelerate the jet, causing the pile up of ions on the jet side and the compression of the magnetic structure on the downstream side. Our study explains the observed properties of bow waves, and helps to better understand the evolution of HSJs.