Lorentz Force Research Articles

Induced electric fields in MRI settings and electric vestibular stimulations: same vestibular effects?

In Magnetic Resonance Imaging scanner environments, the continuous Lorentz Force is a potent vestibular stimulation. It is nowadays so well known that it is now identified as Magnetic vestibular stimulation (MVS). Alongside MVS, some authors argue that through induced electric fields, electromagnetic induction could also trigger the vestibular system. Indeed, for decades, vestibular-specific electric stimulations (EVS) have been known to precisely impact all vestibular pathways. Here, we go through the literature, looking at potential time varying magnetic field induced vestibular outcomes in MRI settings and comparing them with EVS-known outcomes. To date, although theoretically induction could trigger vestibular responses the behavioral evidence remains poor. Finally, more vestibular-specific work is needed.

Numerical study on the behavior of a polymeric MHD nanofluid: entropy optimization and thermal analysis

PurposeAnalyzing and reducing entropy generation is useful for enhancing the thermodynamic performance of engineering systems. This study aims to explore how polymers and nanoparticles in the presence of Lorentz forces influence the fluid behavior and heat transfer characteristics to lessen energy loss and entropy generation.Design/methodology/approachThe dispersion model is initially used to examine the behavior of polymer additives over a magnetized surface. The governing system of partial differential equations (PDEs) is subsequently reduced through the utilization of similarity transformation techniques. Entropy analysis is primarily performed through the implementation of numerical computations on a non-Newtonian polymeric FENE-P model.FindingsThe numerical simulations conducted in the presence of Lorentz forces provide significant insights into the consequences of adding polymers to the base fluid. The findings suggest that such an approach minimizes entropy in the flow region. Through the utilization of polymer-MHD (magnetohydrodynamic) interactions, it is feasible to reduce energy loss and improve the efficiency of the system.Originality/valueThis study’s primary motivation and novelty lie in examining the significance of polymer additives as agents that reduce entropy generation on a magnetic surface. The author looks at how nanofluids affect the development of entropy and the loss of irreversibility. To do this, the author uses the Lorentz force, the Soret effect and the Dufour effect to minimize entropy. The findings contribute to fluid mechanics and thermodynamics by providing valuable insights for engineering systems to increase energy efficiency and conserve resources.

Thermal distribution and viscous heating of electromagnetic radiative Eyring–Powell fluid with slippery wall conditions

The research examines the intricate between Eyring-Powell microfluidic heat transfer, electromagnetic radiation and viscous heating in a Riga slippery device as applied in heat exchangers, cooling systems, biomedical devices, energy generation, polymer processing, and others. The viscoelastic property of the fluid is characterized by the Eyring-Powell Cauchy fluid model with shear-thickening and shear-thinning phenomena that are useful in several heat transport processes and thermal management. The developed governing model is taken from the constitutive relations and conservation principles and solved via an adaptive partition weighted residual method. The essential fluid term sensitivities are systematically investigated on the flow and thermal distribution characteristics. An appropriate validation and comparison of results is done and found to agree quantitatively, this confirmed the correctness of the presented outcomes. The results reveal the significant impact of the thermofluidic terms interaction on the viscous flowing fluid and thermal behaviour. As seen, slip conditions momentously increase the flow rate gradients for about 1.7% to 2.4% close to the boundary wall and consequently raise the microfluidic thermal propagation rates with 3.7% non-Newtonian fluid and thickness of the boundary layer. Moreover, the thermal gradient and distribution complexities are modulated within the fluid regime due to radiation and Lorentz force.

Local plastic deformation effects on the critical current of high-Jc Nb3Sn strands under uniaxial strain

Abstract In order to meet the target operating parameters of the toroidal field coils (TFC) for the next-generation Chinese compact burning plasma tokamak, high critical current density (Jc) Nb3Sn strand will be applied to the high-field winding-package (WP) of the TFC. To improve the transverse stiffness of the cable in withstanding the huge Lorentz force and avoiding conductor performance degradation, the Short-Twist-Pitch (STP) and Copper-Wound-Strand (CWS) cable patterns were taken into consideration. In the processes of cabling and compaction of the conductor, the tight cable configurations lead to severe local plastic deformation (LPD) within the strands. The strands in the conductor are subjected to strain caused by thermal contraction and Lorentz force during conductor cooling down and operation. So far it is unknown, whether the LPD could impact the critical current (Ic) versus uniaxial applied strain behaviour of high-Jc Nb3Sn strand. Aiming to investigate the effect of LPD on the Ic of strands under uniaxial strain, three types of high Jc Nb3Sn strand with different indentation depths were tested on a U-shaped bending spring. The axial strain ranges from -0.9% to +0.4% at 14 T and 4.2 K. The three types of strands showed more strain sensitivity and lower tensile irreversible strain limit with increasing LPD, while even irreversible degradation of the Ic could be observed in the compressive strain region. The sample preparation, test process, test results and analysis are reported.

Computational study of magnetohydrodynamic squeeze flow between infinite parallel disks

This paper explores the magnetohydrodynamic (MHD) squeeze flow of an electrically conducting fluid between two infinite parallel disks with a perpendicular magnetic field. The study focuses on the case where the upper disk moves towards a stationary lower disk. By employing similarity variables, we reduce the MHD momentum and continuity equations into a fourth-order linear boundary value problem, solved using a modified operational matrix method. The numerical approach is validated through L2-truncation error analysis, boundary condition comparisons, and by comparing results with other methods like HAM, HPM, and bvp4c that produce analytical and numerical solutions. Graphical analyses reveal the effects of the squeeze number, Hartman number, and the boundary parameter on velocity and flow profile. Results indicate that the Hartman number significantly affects the velocity due to the Lorentz force, while the squeeze number and boundary parameter influence the velocity and flow profile differently in suction and injection cases. The numerical solution demonstrates high accuracy and convergence compared to previous methods in terms of absolute error.

Thermal and Computational Analysis of MHD Dissipative Flow of Eyring-Powell Fluid: Non-Similar Approach via Overlapping Grid-Based Spectral Collocation Scheme

The aim of the present study is to numerically investigate the non-similar flow and heat transfer in a dissipative Eyring-Powell fluid (EPF) over a stretching surface. A constant magnetic field is applied perpendicular to the stretched surface to explore the impact of the Lorentz force. Both viscous and magnetic dissipation are considered to comprehensively examine their effects on heat transfer. The problem in hand does not admit self-similar solutions as the non-Newtonian fluid parameter varies with the spatial variable along the stream-wise direction. Consequently, the set of nonlinear partial differential equations, modeling the flow problem is nondimensionalized primarily by employing a pseudo-similarity variable and stream-wise coordinate. The non-dimensional set of nonlinear partial differential equations is solved by a newly developed and efficient “overlapping multi-domain bivariate spectral local linearization method (OMD-BSLLM)”. The current study includes residual error analysis and convergence tests to demonstrate the accuracy of the numerical method applied to the current mathematical model. Graphs show fluid flow and heat transfer results for different flow parameters, while tables display skin friction and Nusselt number values. The results indicate that the non-Newtonian fluid parameter enhances both the velocity profile and temperature distribution. The fluid decelerates with increasing the dimensionless stream wise coordinate and Hartmann number. Viscous dissipation and dimensionless stream-wise coordinate enhances the temperature profile.

Effects of viscous and Joule dissipation on hydromagnetic hybrid nanofluid flow over nonlinear stretching surface with Hamilton-Crosser model

Hybrid nanofluids are crucial for enhancing thermal management, efficiency, and longevity in industrial applications such as heat exchangers, automotive cooling, and advanced manufacturing. The current study primarily investigates the impact of viscous and Joule dissipation on copper-alumina hybrid nanofluid flow over a stretching surface, with a particular focus on magnetic field effects resulting in a strong Lorentz force along the vertical direction. The governing equations are non-dimensionalized using similarity transformations, resulting in coupled, highly nonlinear ordinary differential equations (ODEs). The coupled system of ODEs is solved numerically using the Shooting technique and a fourth-order Runge-Kutta scheme in MATLAB. The results are plotted graphically. The outcomes mainly indicate that at the surface, momentum intensifies with increased stretching but declines significantly under a stronger magnetic field, while reduced permeability slows down flow momentum, resulting in higher temperature elevations. The outcomes revealed that copper-alumina hybrid nanofluids with lower permeability could improve the performance of miniature industrial devices.

Photospheric Pore Rotation Associated with a C-class Flare from Spectropolarimetric Observations with DKIST

We present high-resolution observations of a C4.1-class solar flare (SOL2023-05-03T20:53) in AR 13293 from the Visible Spectro-Polarimeter (ViSP) and Visible Broadband Imager (VBI) instruments at the DKIST. The fast cadence, good resolution, and high polarimetric sensitivity of ViSP data provide a unique opportunity to explore the photospheric magnetic fields before and during the flare. We infer the magnetic field vector in the photosphere from the Fe i 6302 Å line using Milne–Eddington inversions. Combined analysis of the inverted data and VBI images reveals the presence of two opposite polarity pores exhibiting rotational motion both prior to and throughout the flare event. Data-driven simulations further reveal a complex magnetic field topology above the rotating pores, including a null-point-like configuration. We observed a 30% relative change in the horizontal component (δ F h ) of Lorentz force at the flare peak time and roughly no change in the radial component. We find that the changes in δ F h are the most likely driver of the observed pore rotation. These findings collectively suggest that the back reaction of magnetic field line reconfiguration in the corona may influence the magnetic morphology and rotation of pores in the photosphere on a significantly smaller scale.

Enhanced heat transfer in novel star-shaped enclosure with hybrid nanofluids: A neural network-assisted study

The current research is a numerical investigation of the thermo-fluidic transport trend within a new star-shaped enclosure filled with Fe3O4−MWCNT (Multiwall Carbon Nanotubes) suspended hybrid nanoparticles in a base fluid (water), induced by a horizontal magnetizing field. A rectangular rod inside the cavity positioned at center is kept at a high temperature, as the low temperature is chosen for outer corrugated boundary. Formulation yelled in mathematical principles, along with the boundary conditions and some physical assumptions, are formulated as dimensionless PDEs. The finite element method (FEM) assisted by “COMSOL” software, employed for numerical simulations, and the PARDISO solver is used for solving nonlinear system of equations. Also, an artificial neural network (ANN) model is assembled to analyze the effect of these parameters on thermal and flow transport properties of Hybrid nanofluid. The training of this ANN model is done by a dataset generated from numerical simulations, suggesting predictions regarding heat transport under varying parameters. This approach does not only reduce the effort, but also reduces computing time when exploring the thermal behaviors across various datasets. The visualization of velocity and temperature fields through streamlines and isotherms, along with the evaluation of the Nusselt number, illustrate the enhanced heat transfer facilitated by the incorporation of Fe3O4−MWCNT nanoparticles. The results show that increased magnetic field strength reduces fluid velocity due to the generated Lorentz force, which counteracts convective flow. Percentage analysis indicates that hybrid nanofluids (Fe3O4−MWCNT) significantly improve thermal distribution compared to conventional fluids. This study demonstrates the effectiveness of ANN models in forecasting the influence of diverse factors on the flow and heat transport characteristics of hybrid nanofluids. These insights are essential to the design and optimization of heat transfer systems.

Magnetic field-augmented photoelectrochemical water splitting in Co3O4 and NiO nanorod arrays

Effective charge separation is crucial for improving the sensitivity of photoelectrochemical studies. Here, we provide an immense magnetic field-based electron spin polarization approach for an efficient charge carrier separation. We have fabricated NiO and Co3O4 thin film and nanorod arrays by electron beam evaporation glancing angle method followed by annealing in a two-zone furnace. The photoelectrochemical performance was investigated for NiO and Co3O4 samples in the presence and absence of a magnetic field. The NiO and Co3O4 nanorods array samples exhibit better absorption compared with the thin film samples. The Co3O4 and NiO nanorod arrays showed the highest photocurrent density of 0.12 and 0.55 mA/cm2 in a magnetic field. The superior photoelectrochemical response of NiO and Co3O4 nanorods in a magnetic field could be ascribed to the limitation of non-radiative recombination of carriers manipulated by Lorentz force and spin polarization. Furthermore, the electrochemical impedance spectra of NiO and Co3O4 nanorod arrays in a magnetic field show the least charge transfer resistance. This study sheds light on the interaction process between external fields and radiative/non-radiative recombination of manipulating carriers. Thus, the application of a magnetic field presents an efficient and versatile approach to enhance the performance of photoelectrodes in solar water splitting.

Tailoring performance for biomass tar reforming using magnetically assisted gliding arc discharges

Gliding arc discharge (GAD) holds significant potential for energy and environmental applications, particularly in biomass tar reforming. In this study, we developed two GAD reactors coupled with a magnetic field for biomass tar reforming. The reactors were designed with two different configurations by varying the magnetic field direction relative to the electrodes: magnetically accelerated gliding arc discharge (MAGAD) and magnetically stabilized gliding arc discharge (MSGAD). The reforming performance and discharge characteristics of these two configurations were systematically evaluated and compared with those of a normal GAD (NGAD). MAGAD demonstrated superior reforming performance, achieving the highest conversion for toluene (71.4 %) and phenol (87.5 %), as well as the highest yields of H2 (22.4 %) and C2H2 (12.6 %) at a magnetic field intensity of 133 mT. In contrast, MSGAD achieved the highest energy yield (47.1 g/kWh) but exhibited lower tar conversion due to reduced discharge power. In the MAGAD system, the magnetic field generates a synergistic effect between the Lorenz force and gas thrust, accelerating and elongating the arc along the electrodes. This results in increased discharge power and frequency, as well as an expanded discharge region. This leads to the generation of more reactive species, which enhances the breakdown of benzene rings into short-chain hydrocarbons and reduces the formation of liquid byproducts. These findings demonstrate the potential of manipulating magnetic fields to optimize GAD systems for efficient biomass tar reforming, offering a promising strategy to improve the performance of plasma-based chemical reactions.

Synergistic effects of multi-segmented magnetic fields, wavy-segmented cooling, and distributed heating on hybrid nanofluid convective flow in tilted porous enclosures

This study investigates the complex thermal-fluid behavior within a tilted porous enclosure filled with a Cu−Al2O3-water hybrid nanofluid, subject to segmented magnetic fields, wavy cooling segments, and distributed heat sources. The research explores the intricate interplay between geometric factors and thermal-magnetic forces to enhance heat transfer in industrial applications. The finite volume method (FVM), coupled with the SIMPLE algorithm and a TDMA solver, is employed to solve the governing transport equations. A comprehensive parametric analysis examines the effects of key dimensionless parameters: Darcy-Rayleigh number (10–104), Darcy number (10-4–10-1), Hartmann number (0–70), magnetic field angle (0°-180°), nanoparticle volume fraction (0–2 %), porosity (0.1–1.0), wavy cooler undulation height (0–0.3), magnetic segment width (0–1), number of segmental magnetic fields (0–4), and enclosure tilting angle (0°–180°). The study elucidates the physical mechanisms underlying the transition from uniform to segmented heating scenarios. Results reveal a remarkable enhancement of up to 38 % in heat transfer performance when transitioning from a conventional square enclosure to the proposed configuration with partial waviness on opposing walls. This improvement stems from increased surface area and disrupted thermal boundary layers, promoting better fluid mixing. The application of a segmented magnetic field with strategic orientation resulted in up to 26 % enhancement by modulating flow patterns and creating localized convection cells. The segmented heating generates thermal plumes that interact with the magnetic field-induced Lorentz forces, further improving thermal transport. The findings provide valuable insights into the design and optimization of efficient heat transfer systems in various industries, including electronics cooling, solar thermal collectors, and nuclear reactors, demonstrating significant potential for energy savings and improved thermal management through the strategic integration of hybrid nanofluids, magnetic fields, and geometric modifications in porous media applications.

Research on Auxiliary Effect of Lorentz Force for On-orbit Servicing of Spacecraft

Background: On-orbit servicing of spacecraft is mainly aimed at repairing failed spacecraft, maintaining and upgrading normally operating spacecraft to extend their life in order to reduce the increase of space debris and maintain the space environment. Objective: In performing on-orbit servicing, the spacecraft typically requires continuous control force to hover for a long period of time in order to maintain a relatively stationary state towards the target. Methods: Considering the limited amount of fuel carried, the Lorentz force is introduced into onorbit servicing to assist spacecraft in hovering. In order to demonstrate the feasibility of using Lorentz force as spacecraft thrust, many related patents have been provided. Results: Firstly, the velocity of the spacecraft's orbital motion and the variation of the geomagnetic field were given, and the specific expression of the Lorentz force in the relative dynamics model of the spacecraft was deduced. When studying the auxiliary effect of Lorentz force, a critical angle was defined. The relation between the critical angle and the Lorentz force on the auxiliary effect of spacecraft hovering was analyzed through numerical examples. Conclusion: Furthermore, based on the influence of the charge-to-mass ratio on the critical angle, the variation law of the Lorentz force-assisted spacecraft hovering area with different charge-tomass ratios was derived.

Magnetic Activation: A Novel Approach to Enhance Hydrogen Evolution Activity of Co0.85Se@CNTs Heterostructured Catalyst.

The heterostructure strategy is currently an effective method for enhancing the catalytic activity of materials. However, the challenge that is how to further improve their catalytic performance, based on the principles of material modification is must addressed. Herein, a strategy is introduced for magnetically regulating the catalytic activity to further enhance the hydrogen evolution reaction (HER) activity for Co0.85Se@CNTs heterostructured catalyst. Building on heterostructure modulation, an external alternating magnetic field (AMF) is introduced to enhance the electronic localization at the active sites, which significantly boosts catalytic performance (71 to 43mV at 10mA cm-2). To elucidate the catalytic mechanism, especially under the influence of the AMF, in situ Raman spectroscopy is innovatively applied to monitor the HER process of Co0.85Se@CNTs, comparing conditions with and without the AMF. This study demonstrates that introducing the AMF does not induce a change in the true active site. Importantly, it shows that the Lorentz force generated by the AMF enhances HER activity by promoting water molecule adsorption and O─H bond cleavage, with the Stark tuning rate indicating increased water interaction and bond cleavage efficiency. Theoretical calculations further support that the AMF optimizes energy barriers for key reaction intermediates (steps of *H2O-TS and *H+*1/2H2).

Identification of Kelvin-Helmholtz generated vortices in magnetised fluids

The Kelvin-Helmholtz Instability (KHI), arising from velocity shear across the magnetopause, plays a significant role in the viscous-like transfer of mass, momentum, and energy from the shocked solar wind into the magnetosphere. While the KHI leads to growth of surface waves and vortices, suitable detection methods for these applicable to magnetohydrodynamics (MHD) are currently lacking. A novel method is derived based on the well-established λ-family of hydrodynamic vortex identification techniques, which define a vortex as a local minimum in an adapted pressure field. The J×B Lorentz force is incorporated into this method by using an effective total pressure in MHD, including both magnetic pressure and a pressure-like part of the magnetic tension derived from a Helmholtz decomposition. The λMHD method is shown to comprise of four physical effects: vortical momentum, density gradients, fluid compressibility, and the rotational part of the magnetic tension. A local three-dimensional MHD simulation representative of near-flank magnetopause conditions (plasma β’s 0.5–5 and convective Mach numbers Mf∼0.4) under northward interplanetary magnetic field (IMF) is used to validate λMHD. Analysis shows it correlates well with hydrodynamic vortex definitions, though the level of correlation decreases with vortex evolution. Overall, vortical momentum dominates λMHD at all times. During the linear growth phase, density gradients act to oppose vortex formation. By the highly nonlinear stage, the formation of small-scale structures leads to a rising importance of the magnetic tension. Compressibility was found to be insignificant throughout. Finally, a demonstration of this method adapted to tetrahedral spacecraft observations is performed.

Impact of viscous dissipation on MHD flow of Maxwell nanofluid across a linear stretching sheet

The viscous dissipation of Maxwell nanofluid movement on a stretching sheet is examined in the present article. Constructed the modelling equalities with assumptions and emerging parameters such as Magnetic parameters, thermophoresis, Brownian motion, and Biot number etc. Convert those equation to simple third-order ODEs by applying stream functions, MATHEMATICA software used to solve ODE by applying the RK method approach with shooting technique. Presented our outcomes graphically by incorporating the parameters. The elasticity of the Maxwell fluid is directly proportional to temperature, resulting in a reduction in its velocity. The factors that affect fluid flow include viscous dissipation, Lewis number, Brownian motion, and the reversibility of temperature and velocity. Increasing the parameters of Brownian motion leads to significant movement of the nanofluid particles, which in turn increases their kinetic energy and enhances heat generation in the boundary layer. The Lorentz force, which hinders the movement of fluid, leads to a decrease in velocity profiles. This is determined by the magnetic parameter. The heat transfer rate, the velocity decay rate, and the occurrence of viscous dissipation are all occurring in close proximity to the sheet. Also, the model tabular validation presented and current results align well with previously published studies. Cancer treatment and the cooling process in industries, polymer processing, biotechnology and medicine, food industry, cosmetics, oil and gas, textiles, aerospace and automotive, and construction are just a few of the technical and biological uses for it. Industries may enhance material performance, process efficiency, and product quality in a variety of applications by using Maxwell fluid models.

Characteristics of wave propagation in pre-stressed viscoelastic Timoshenko nanobeams with surface stress and magnetic field influences

The current investigation explores the behavior of pre-stressed viscoelastic Timoshenko nanobeams under the influence of surface effects and a longitudinal magnetic field. Utilizing a modified version of non-local strain gradient theory through the Kelvin–Voigt viscoelastic model, a closed-form dispersion relation using a suitable analytical approach has been derived. To account for surface stresses, Gurtin–Murdouch surface elasticity theory has been employed. Additionally, the study delves into the impact of a longitudinal magnetic field on a single-walled carbon nanotube, considering Lorentz magnetic forces. The validity of the findings is established by deriving results in the absence of surface effects and magnetic fields, aligning well with existing literature. The investigation indicates that pre-stress has marginal effects on flexural and shear waves, while surface effects, magnetic fields, non-locality, characteristic length, and nanotube diameter significantly influence the phase velocity. Additionally, the threshold velocity and blocking diameter are discussed for the model.

Multi-Body Dynamics Modeling and Simulation of Maglev Satellites

The Lorentz force magnetic levitation gim2bal stabilized platform (LFMP), as a new generation of high-precision turntable for maglev satellites, can meet the requirements of future spacecraft for ultra-high attitude pointing accuracy and stability. To solve the problem of three-module multi-body attitude control under maneuvering conditions, the platform subsystem is first dynamically modeled based on the second type of Lagrangian equation, and the payload subsystem is dynamically modeled based on the Newton–Euler method. Secondly, a multi-loop control system is designed, consisting of high-precision and fast attitude pointing control for the payload, position tracking control for the platform subsystem, and tracking control for the maglev module. The final simulation results verified the feasibility and effectiveness of the payload-centered control method. An evaluation of the stability with a specific model has been performed, and the attitude accuracy of the payload is within 0.00002° and the attitude stability is within 0.00005°/s.

Entropy optimization in ternary hybrid nanofluid flow over a convectively heated bidirectional stretching sheet with Lorentz forces and viscous dissipation: A Cattaneo–Christov heat flux model

Bidirectional stretching sheet models can represent surfaces in heat exchangers where fluids flow under continuous deformation. Ternary hybrid nanofluids could be employed in these systems to increase heat transfer rates between fluids in heat exchangers and improve the efficiency of energy conversion processes. In this work, we explore the novel application of a ternary hybrid nanofluid (water with titanium dioxide, cobalt ferrite, and magnesium oxide nanoparticles) for enhanced heat transfer in heat exchangers modeled by a bidirectional stretching sheet. This approach offers a potential advancement over traditional nanofluids (with one or two nanoparticles). Furthermore, we present a comprehensive analysis that incorporates ohmic heating, Cattaneo–Christov heat flux, thermal radiation, viscous dissipation, and irreversibility. The governing equations are transformed into a system of nonlinear ordinary differential equations using appropriate similarity transformations and then solved using the bvp4c solver, a MATLAB built-in function. This study's findings reveal that the Eckert number and radiation parameter increase fluid temperature, while the thermal relaxation parameter leads to a reduction in the temperature of the fluid. It is detected that an increase in magnetic field parameter and volume fraction of [Formula: see text] results in a decline of the skin friction factors in both directions. It is revealed that there is a reduction in the Nusselt number with the rise in Eckert number ([Formula: see text]), and the same number declines at a rate of 0.8252 when [Formula: see text]. It is noticed that the skin friction coefficient declines at a rate of 0.62179204 (in case of x-direction) and 0.621791816 (in case of y-direction), respectively, when the values of magnetic field parameter lie between 0 and 3.5. Furthermore, it is noticed that an upsurge in thermal relaxation parameter results in a fall in the temperature of the fluid.

The Dzhanibekov Effect as a Possible Source of Magnetar Activity

Magnetars, which are neutron stars with strong magnetic fields, exhibit occasional bursting activities. The shape of a magnetar is not perfectly spherical due to the Lorentz force exerted by its strong magnetic fields and is described as a triaxial body. We study the unstable free precession in a triaxial magnetar; one of the principal axes undergoes an upside-down flip. This flip is known as the Dzhanibekov effect. We find that during the flip, the Euler force can suddenly disturb the force balance on the surface layer of the magnetar, potentially leading to plastic flow of the layer. This, in turn, may trigger different forms of magnetar activity, such as the emission of the bursts and/or of gravitational waves.