Self-consistent treatment of cyclotron resonances in inhomogeneous plasmas

1990 ◽  
Vol 43 (1) ◽  
pp. 151-163 ◽  
Author(s):  
B. M. Harvey ◽  
E. W. Laing
Keyword(s):  
Magnetic Field ◽  
Mode Conversion ◽  
Magnetic Field Gradient ◽  
Process Conditions ◽  
Fast Wave ◽  
Linear Mode ◽  
Consistent Treatment ◽  
Bernstein Wave ◽  
The Magnetic Field ◽  
Transmission And Reflection

The wave differential operator is obtained directly from the perturbed Vlasov equation for an inhomogeneous equilibrium magnetic field including consistently the effects of strong wave damping and linear mode conversion. In the process, conditions on the parallel wavenumber and the magnetic-field gradient for which such a method is valid are obtained. From these equations it is shown that the inclusion of parameter-gradient terms arising from the spatial dependence of the equilibrium magnetic field is important for accurate calculation of mode conversion from fast to ion-Bernstein wave, although the dispersion-relation-based operator can be sufficient to describe transmission and reflection of the fast wave. Finally, the coupled second-order equations used by Fuchs & Bers (1988) are obtained, allowing direct identification of the ‘modes’ referred to in that paper in terms of components of the electric field. By reconciling these two different approaches, some insight is gained into the mode-conversion process.

scholarly journals Bernstein mode acceleration of electrons in a magnetic mirror

2020 ◽  
Vol 38 (2) ◽  
pp. 79-83
Author(s):  
Ram Jeet ◽  
Asheel Kumar
Keyword(s):  
Magnetic Field ◽  
Transverse Energy ◽  
Mode Conversion ◽  
Magnetic Mirror ◽  
Electron Dynamics ◽  
Linear Mode ◽  
Gain Energy ◽  
Normalized Parameters ◽  
Electron Cyclotron Wave ◽  
Bernstein Wave

AbstractElectron dynamics in an axially localized large amplitude electron Bernstein mode in a magnetic mirror is studied. The mode is localized due to plasma density and magnetic field profiles and could be driven by an electron cyclotron wave, launched from outside, via linear mode conversion. Energetic electrons of finite gyro-radius resonantly interact with the mode and gain primarily transverse energy favoring stronger mirror confinement. At Bernstein wave normalized amplitude of A00 = 0.01 and for other normalized parameters Zn0 = 40, k⊥c/ω = 10, ${L}^{\prime}_m = 215$, ωc0/ω = 0.9, ψn0 = 3π/2, the electrons can gain energy in the hundreds of keV range.

scholarly journals Remote manipulation of magnetic nanoparticles using magnetic field gradient to promote cancer cell death

2018 ◽  
Author(s):  
Mahendran Subramanian ◽  
Arkadiusz Miaskowski ◽  
Stuart Iain Jenkins ◽  
Jenson Lim ◽  
Jon Dobson
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Field Gradient ◽  
Biomedical Applications ◽  
Magnetic Field Gradient ◽  
Field Source ◽  
Remote Manipulation ◽  
Cancer Cell Death ◽  
The Magnetic Field

AbstractThe manipulation of magnetic nanoparticles (MNPs) using an external magnetic field, has been demonstrated to be useful in various biomedical applications. Some techniques have evolved utilizing this non-invasive external stimulus but the scientific community widely adopts few, and there is an excellent potential for more novel methods. The primary focus of this study is on understanding the manipulation of MNPs by a time-varying static magnetic field and how this can be used, at different frequencies and displacement, to manipulate cellular function. Here we explore, using numerical modeling, the physical mechanism which underlies this kind of manipulation, and we discuss potential improvements which would enhance such manipulation with its use in biomedical applications, i.e., increasing the MNP response by improving the field parameters. From our observations and other related studies, we infer that such manipulation depends mostly on the magnetic field gradient, the magnetic susceptibility and size of the MNPs, the magnet array oscillating frequency, the viscosity of the medium surrounding MNPs, and the distance between the magnetic field source and the MNPs. Additionally, we demonstrate cytotoxicity in neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cells in vitro. This was induced by incubation with MNPs, followed by exposure to a magnetic field gradient, physically oscillating at various frequencies and displacement amplitudes. Even though this technique reliably produces MNP endocytosis and/or cytotoxicity, a better biophysical understanding is required to develop the mechanism used for this precision manipulation of MNPs, in vitro.

scholarly journals Magnetorheological Fluids Behaviour in Oscillatory Compression Squeeze: Experimental Testing and Analysis

2019 ◽  
Vol 13 (4) ◽  
pp. 221-225
Author(s):  
Wojciech Horak ◽  
Marcin Szczęch ◽  
Bogdan Sapiński
Keyword(s):  
Magnetic Field ◽  
Volume Fraction ◽  
Experimental Testing ◽  
Magnetic Field Gradient ◽  
Particle Volume Fraction ◽  
Excitation Frequency ◽  
Magnetorheological Fluid ◽  
Density Level ◽  
Particle Volume ◽  
The Magnetic Field

Abstract This article deals with experimental testing of magnetorheological fluid (MRF) behaviour in the oscillatory squeeze mode. The authors investigate and analyse the influence of excitation frequency and magnetic field density level on axial force in MRFs that differ in particle volume fraction. The results show that, under certain conditions, the phenomenon of self-sealing can occur as a result of the magnetic field gradient and a vacuum in the working gap of the system.

Precisely mapping the magnetic field gradient in vacuum with an atom interferometer

2010 ◽  
Vol 82 (6) ◽  
Author(s):  
Min-Kang Zhou ◽  
Zhong-Kun Hu ◽  
Xiao-Chun Duan ◽  
Bu-Liang Sun ◽  
Jin-Bo Zhao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Magnetic Field Gradient ◽  
Atom Interferometer ◽  
The Magnetic Field

Design and Analysis of a Vibration-Based Magnetoelectric Energy Harvesting Device

2013 ◽  
Vol 722 ◽  
pp. 75-80 ◽  
Author(s):  
Zhang Zhang ◽  
Xian Zhi Dai ◽  
Yong Wang
Keyword(s):  
Magnetic Field ◽  
Cantilever Beam ◽  
Magnetic Circuit ◽  
Magnetic Field Gradient ◽  
Sensor Nodes ◽  
Ambient Vibration ◽  
Gradient Magnetic Field ◽  
Wireless Sensor Nodes ◽  
The Magnetic Field ◽  
Theoretical Results

An energy harvester is presented to harvest ambient vibration energy using a cantilever beam and multiple Terfenol-D/PMN-PT/Terfenol-D laminate magnetoelectric transducers. The harvester uses eight magnets to make up a magnetic circuit arranged on the free end of the cantilever beam. The magnetic circuit can produce a high gradient magnetic field space. The multiple transducers are placed at the high magnetic field gradient position to make the best use of the magnetic field produced by the magnets. The nonlinear vibration and electrical-output performances of the harvester at resonance are analyzed. The theoretical results indicate that the prototype can produce a load power of 7.619 mW, which is sufficient to supply low consumption wireless sensor nodes.

On Geometrical Invariants of the Magnetic Field Gradient Tensor in Turbulent Space Plasmas: Scale Variability in the Inertial Range

2019 ◽  
Vol 878 (2) ◽  
pp. 124 ◽  
Author(s):  
Virgilio Quattrociocchi ◽  
Giuseppe Consolini ◽  
Maria Federica Marcucci ◽  
Massimo Materassi
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Magnetic Field Gradient ◽  
Inertial Range ◽  
Space Plasmas ◽  
Gradient Tensor ◽  
The Magnetic Field

Effects of the magnetic field gradient on the wall power deposition of Hall thrusters

2017 ◽  
Vol 83 (2) ◽  
Author(s):  
Yongjie Ding ◽  
Peng Li ◽  
Xu Zhang ◽  
Liqiu Wei ◽  
Hezhi Sun ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Discharge Channel ◽  
Magnetic Field Gradient ◽  
Zero Magnetic Field ◽  
Power Deposition ◽  
Neutral Gas ◽  
Channel Exit ◽  
Ionization Region ◽  
The Magnetic Field

The effect of the magnetic field gradient in the discharge channel of a Hall thruster on the ionization of the neutral gas and power deposition on the wall is studied through adopting the 2D-3V particle-in-cell (PIC) and Monte Carlo collisions (MCC) model. The research shows that by gradually increasing the magnetic field gradient while keeping the maximum magnetic intensity at the channel exit and the anode position unchanged, the ionization region moves towards the channel exit and then a second ionization region appears near the anode region. Meanwhile, power deposition on the walls decreases initially and then increases. To avoid power deposition on the walls produced by electrons and ions which are ionized in the second ionization region, the anode position is moved towards the channel exit as the magnetic field gradient is increased; when the anode position remains at the zero magnetic field position, power deposition on the walls decreases, which can effectively reduce the temperature and thermal load of the discharge channel.

Numerical modelling of MHD waves in the solar chromosphere

2005 ◽  
Vol 364 (1839) ◽  
pp. 395-404 ◽  
Author(s):  
Mats Carlsson ◽  
Thomas J Bogdan
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Mode Conversion ◽  
Three Dimensions ◽  
Mhd Waves ◽  
Solar Chromosphere ◽  
Fast Mode ◽  
Reflected Waves ◽  
The Waves ◽  
The Magnetic Field

Acoustic waves are generated by the convective motions in the solar convection zone. When propagating upwards into the chromosphere they reach the height where the sound speed equals the Alfvén speed and they undergo mode conversion, refraction and reflection. We use numerical simulations to study these processes in realistic configurations where the wavelength of the waves is similar to the length scales of the magnetic field. Even though this regime is outside the validity of previous analytic studies or studies using ray-tracing theory, we show that some of their basic results remain valid: the critical quantity for mode conversion is the angle between the magnetic field and the k-vector: the attack angle. At angles smaller than 30° much of the acoustic, fast mode from the photosphere is transmitted as an acoustic, slow mode propagating along the field lines. At larger angles, most of the energy is refracted/reflected and returns as a fast mode creating an interference pattern between the upward and downward propagating waves. In three-dimensions, this interference between waves at small angles creates patterns with large horizontal phase speeds, especially close to magnetic field concentrations. When damping from shock dissipation and radiation is taken into account, the waves in the low–mid chromosphere have mostly the character of upward propagating acoustic waves and it is only close to the reflecting layer we get similar amplitudes for the upward propagating and refracted/reflected waves. The oscillatory power is suppressed in magnetic field concentrations and enhanced in ring-formed patterns around them. The complex interference patterns caused by mode-conversion, refraction and reflection, even with simple incident waves and in simple magnetic field geometries, make direct inversion of observables exceedingly difficult. In a dynamic chromosphere it is doubtful if the determination of mean quantities is even meaningful.

Magnetic Targeting of Particle Transport Under Pulsatile Flow

2006 ◽  
Author(s):  
Alicia Williams ◽  
Ashok Sinha ◽  
Pavlos Vlachos ◽  
Ishwar K. Puri
Keyword(s):  
Magnetic Field ◽  
Pulsatile Flow ◽  
Magnetic Particles ◽  
Colloidal Suspension ◽  
Magnetic Field Gradient ◽  
Colloidal Suspensions ◽  
Glass Tube ◽  
Superparamagnetic Nanoparticles ◽  
Magnetic Drug Targeting ◽  
The Magnetic Field

Magnetic Drug Targeting (MDT) has been shown to be a promising technique to effectively deliver medicinal drugs via functionalized [1] magnetic particles to target sites during the treatment of cancer and other diseases [2,3,4]. In this paper, we investigate the interaction of steady and pulsatile flows injected with a ferrofluid, which is a colloidal suspension of superparamagnetic nanoparticles in a glass tube under the influence of a magnetic field. Ferrofluids are colloidal suspensions of single domain magnetic nanoparticles that are of the order of 10 nm in diameter. In this experiment, the ferrofluid particles were directed to a particular region of interest within a 10 mm diameter glass vessel by means of an applied localized magnetic field that originated outside of the vessel. The magnetic field was generated using a rare earth sintered permanent magnet which produced the magnetic field gradient required for inducing a body force on the volume of the ferrofluid. The experimental results reveal flows with rich dynamical phenomena. The aggregation of the ferrofluid produces a self-assembled hemispherical structure which dynamically interacts with the host flow. The aggregation generates an occlusion creating a flow field that is similar to that past an obstruction. However, since the structure itself is of a fluidic nature, it is subject to shear forces caused by the host fluid. In addition, the wake of the flow behind the aggregation creates vortices which are critical to study the stability of the ferrofluid aggregate. This paper presents a detailed investigation of the dynamics of the flow using Time-Resolved Digital Particle Image Velocimetry. To the best of the authors’ knowledge, these are the first quantitative, spatiotemporally resolved measurements documenting the interaction of a host fluid with a ferrofluid aggregate under steady or pulsatile flow conditions.

scholarly journals Influence of magnetic field on change of activation energy during pre-sowing seed treatment

2020 ◽  
pp. 17-25
Author(s):  
V. Savchenko ◽  
◽  
O. Synyavsky ◽  
D. Rosengart ◽  
V. Bunko ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Activation Energy ◽  
Magnetic Induction ◽  
Seed Treatment ◽  
Crop Yields ◽  
Magnetic Field Gradient ◽  
Agricultural Crops ◽  
Experimental Planning ◽  
Sowing Seed ◽  
The Magnetic Field

It is possible to increase crop yields and product quality through the use of electrophysical methods of pre-sowing seed treatment, among which pre-sowing seed treatment in a magnetic field is promising. For successful introduction of magnetic seed treatment in production it is necessary to establish mode parameters of treatment and their optimum values. To do this, it is necessary to establish the effect of the magnetic field on the change in activation energy during pre-sowing seed treatment. The aim of the study was to determine the change in activation energy during pre-sowing treatment of crop seeds in a magnetic field. To determine the change in the activation energy, the change in the biopotential of the seed during its treatment in a magnetic field was experimentally investigated by the experimental planning method. It was found that the change in seed biopotential depends on the square of the magnetic induction and the velocity of the seed in a magnetic field. An analytical expression was obtained that relates the change in activation energy to the change in seed biopotential, which made it possible to establish the dependence of the change in activation energy on the treatment parameters. It was found that the greatest seed biopotential and activation energy change at a magnetic induction of 0.065 T, a magnetic field gradient of 0.57 T/m and a velocity of 0.4 m/s. Under this mode of pre-sowing seed treatment of agricultural crops, the activation energy changes by 3.1 - 5.7 kJ/g-eq.

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