scholarly journals The Structure of a Stream of Electrons and Ions Drifting and Diffusing in a Gas When Ionization by Collision and Molecular Attachment are Present

1959 ◽  
Vol 12 (2) ◽  
pp. 171 ◽  
Author(s):  
LGH Huxley
Keyword(s):  
Magnetic Field ◽  
Point Source ◽  
Line Source ◽  
Electron Attachment ◽  
Uniform Field ◽  
Electrons And Ions

The theory is developed of the structure of a stream of electrons and ions drifting under the action of a uniform field and diffusing in a gas when either or both ionization by collision and electron attachment are present. The cases considered include a point source and a line source, and in the latter case the influence of a magnetic field is discussed.

scholarly journals Magnetoactive elastomers for magnetically tunable vibrating sensor systems

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Tatiana I. Becker ◽  
Yuriy L. Raikher ◽  
Oleg V. Stolbov ◽  
Valter Böhm ◽  
Klaus Zimmermann
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Smart Materials ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Uniform Field ◽  
Sensor Systems ◽  
Ongoing Research ◽  
Amplification Ratio ◽  
Field Distortion

Abstract Magnetoactive elastomers (MAEs) are a special type of smart materials consisting of an elastic matrix with embedded microsized particles that are made of ferromagnetic materials with high or low coercivity. Due to their composition, such elastomers possess unique magnetic field-dependent material properties. The present paper compiles the results of investigations on MAEs towards an approach of their potential application as vibrating sensor elements with adaptable sensitivity. Starting with the model-based and experimental studies of the free vibrational behavior displayed by cantilevers made of MAEs, it is shown that the first bending eigenfrequency of the cantilevers depends strongly on the strength of an applied uniform magnetic field. The investigations of the forced vibration response of MAE beams subjected to in-plane kinematic excitation confirm the possibility of active magnetic control of the amplitude-frequency characteristics. With change of the uniform field strength, the MAE beam reveals different steady-state responses for the same excitation, and the resonance may occur at various ranges of the excitation frequency. Nonlinear dependencies of the amplification ratio on the excitation frequency are obtained for different magnitudes of the applied field. Furthermore, it is shown that the steady-state vibrations of MAE beams can be detected based on the magnetic field distortion. The field difference, which is measured simultaneously on the sides of a vibrating MAE beam, provides a signal with the same frequency as the excitation and an amplitude proportional to the amplitude of resulting vibrations. The presented prototype of the MAE-based vibrating unit with the field-controlled “configuration” can be implemented for realization of acceleration sensor systems with adaptable sensitivity. The ongoing research on MAEs is oriented to the use of other geometrical forms along with beams, e.g. two-dimensional structures such as membranes.

scholarly journals DIFFUSION FROM A LINE SOURCE IN A MAGNETIC FIELD

1963 ◽  
Author(s):  
K Berkner ◽  
R Pyle ◽  
H Rugge ◽  
J Stearns ◽  
J Winocur
Keyword(s):  
Magnetic Field ◽  
Line Source

The Effect of Magnetic Field Spread and Temperature and Density Variations in Cyclotron Emission Regions

1987 ◽  
Vol 7 (2) ◽  
pp. 123-127 ◽  
Author(s):  
D. T. Wickramasinghe ◽  
Lilia Ferrario
Keyword(s):  
Magnetic Field ◽  
Point Source ◽  
Circular Polarization ◽  
White Dwarfs ◽  
Type Systems ◽  
Polar Cap ◽  
Cyclotron Radiation ◽  
Cyclotron Emission ◽  
Source Models ◽  
Accretion Shocks

AbstractWe discuss the properties of cyclotron radiation from accretion shocks located above the atmospheres of magnetic white dwarfs taking into account the effects of field spread and density and temparture structure. The models which are an improvement on previous point source models are shown to have characteristics that are in better overall agreement with the properties of AM Herculis type systems. Our calculations of the polarization properties of large polar cap emission regions are used to discuss the recent null measurements of circular polarization in DQ Herculis type systems.

Influence of time-variable solar wind on the response of Mercury’s magnetosphere

2021 ◽  
Author(s):  
Sae Aizawa ◽  
Nicolas André ◽  
Ronan Modolo ◽  
Elisabeth Werner ◽  
Jim Slavin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Charged Particles ◽  
Time Variable ◽  
Low Energy ◽  
Field Of View ◽  
Plasma Measurement ◽  
Electrons And Ions ◽  
Low Energy Electrons ◽  
The Magnetic Field

<p><span lang="EN-GB">BepiColombo is going to conduct its first Mercury flyby in October 2021. During this flyby,  plasma measurement will be obtained and bring new insights on the Hermean magnetosphere and its interaction with the Sun despite the limited field of view of the instruments during the cruise phase. Unlike Mariner-10 ion measurements will be obtained, and unlike MESSENGER, low energy electrons and ions will be measured simultaneously. In this study, we have revisited Mariner 10 and MESSENGER observations with the help of the global hybrid model LatHyS in order to understand the influence of time-variable solar wind and to constraint the plasma environment. We are able to reproduce the magnetic field observations of Mariner 10 along its trajectory with in particular two distinct signatures consisting of a quiet and disturbed state of the magnetosphere. In addition, the plasma spectrogram is also collected in the model and this enables us to detail the properties of the charged particles observed during the flyby. We will discuss all these signatures both in term of an interaction with a time-variable solar wind and localized processes occurring in the magnetosphere. We will then present the virtual sampling of both the magnetic field and plasma spectrogram along BepiColombo’s first Mercury flyby trajectory and discuss the possible signatures to be observed at that time.</span></p>

Transport of energetic particles from reconnecting current sheets in flaring corona to the heliosphere

2021 ◽  
Author(s):  
Philippa Browning ◽  
Mykola Gordovskyy ◽  
Satashi Inoue ◽  
Eduard Kontar ◽  
Kanya Kusano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energetic Particles ◽  
Transport Processes ◽  
Data Driven ◽  
Current Sheets ◽  
Electrons And Ions ◽  
Data Driven Approach ◽  
Particle Simulations ◽  
The Magnetic Field

<p>In this study, we inverstigate the acceleration of electrons and ions at current sheets in the flaring solar corona, and their transport into the heliosphere. We consider both generic solar flare models and specific flaring events with a data-driven approach. The aim is to answer two questions: (a) what fraction of particles accelerated in different flares can escape into the heliosphere?; and (b) what are the characteristics of the particle populations propagating towards the chromosphere and into the heliosphere?</p><p>We use a combination of data-driven 3D magnetohydrodynamics simulations with drift-kinetic particle simulations to model the evolution of the magnetic field and both thermal and non-thermal plasma and to forward-model observable characteristics. Particles are accelerated in current sheets associated with flaring reconnection. When applied to a specific flare, the model successfully predicts observed features such as the location and relative intensity of hard X-ray sources and helioseismic source locations. This confirms the viability of the approach.</p><p>Using these MHD-particle models, we will show how the magnetic field evolution and particle transport processes affect the characteristics of both energetic electrons and ions in the the inner corona and the heliosphere. The implications for interpretation of in situ measurements of energetic particles by Solar Orbiter and Parker Solar Probe will be discussed.</p><p> </p><p> </p>

scholarly journals Instabilities in a thin current sheet and their consequences

2004 ◽  
Vol 11 (2) ◽  
pp. 153-163 ◽  
Author(s):  
N. Singh
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Drift Velocity ◽  
Early Stage ◽  
Field Configuration ◽  
Central Plane ◽  
Current Disruption ◽  
Electrons And Ions ◽  
Thin Current Sheet ◽  
Electrostatic Fluctuations

Abstract. Using a fully 3-D particle in-cell simulation, we studied the electrodynamics of a thin current sheet (CS). Starting with a uniform plasma and anti-parallel magnetic field, Harris equilibrium is achieved during the early stage of the simulation. In the processes of reaching the equilibrium, both electrons and ions in the newly formed CS are energized and develop pitch-angle anisotropies. We find two distinct stages of primarily electrostatic instabilities; in the first stage the relative drift between electrons and ions drives the instability in the central regions of the CS. The electrostatic fluctuations scatter electrons causing current disruption in the central region. The associated reduction in the average drift velocity of the current-carrying electrons generates sheared flow. The second stage of the instability begins when the drift velocity develops a minimum in the central plane. Then the shear and the growing electrostatic fluctuations under the condition of the maintained anti-parallel driving magnetic field configuration feed each other making the instability explosive. The growing fluctuations create plasma clumps as the electrons and ions are progressively trapped in the large-amplitude waves. The density clumping also generates clumps in the current. The non-uniform current distribution causes magnetic reconnection, accompanied by heating of electrons and ion at a fast rate and nearly complete bifurcation of the current sheet. Anomalous resistivity during different stages of the evolution of the CS is calculated and compared against theory.

scholarly journals Particle Acceleration in Collisionless Magnetic Reconnection

2001 ◽  
Vol 203 ◽  
pp. 555-557
Author(s):  
P. K. Browning ◽  
G. E. Vekstein
Keyword(s):  
Magnetic Field ◽  
Field Component ◽  
Charged Particles ◽  
Energy Spectra ◽  
Uniform Field ◽  
Two Dimensional ◽  
Point Field ◽  
Field Geometry ◽  
Collisionless Reconnection ◽  
Accelerated Particles

We investigate the acceleration of charged particles in the framework of collisionless reconnection. A steady reconnection scenario is considered, with a two dimensional X-point magnetic field geometry having also a uniform field component transverse to the plane of the X-point field, and an inductive electric field generating an inflow of particles. Test particle trajectories are studied, and the energy spectra of the accelerated particles are determined.

scholarly journals Photospheric Sources of Magnetic Field Aligned Currents

1983 ◽  
Vol 71 ◽  
pp. 601-603
Author(s):  
Ake Nordlund
Keyword(s):  
Magnetic Field ◽  
Momentum Transfer ◽  
Coronal Magnetic Field ◽  
Small Scale ◽  
Solar Photosphere ◽  
Electron Component ◽  
Neutral Gas ◽  
Electrons And Ions ◽  
Density Of Electrons ◽  
Gas Component

Possible (small-scale) photospheric sources of coronal magnetic field aligned currents are discussed. Such currents are equivalent to local (small-scale) twists of the coronal magnetic field, and may cause field topologies that are (MHD or resistively) unstable, and thus contribute to the (small-scale) coronal activity.One electro-motive force associated with photospheric magnetic fields is due to the asymmetry between ions and electrons as agents of conductivity and as agents of momentum transfer to the (dominant) neutral gas component. In the solar photosphere, where only some of the easily ionized heavier elements (Mg, Si, Fe, ...) are significantly ionized, the ratio of number density of electrons and ions to neutrals is very small, of the order of the total abundance of these elements, which is of the order 10-4, by number. Due to the larger electron than ion mobility, electric currents are mainly carried by the electron component of the plasma whereas, because of the ions greater momentum transfer to the neutrals in collisions, the friction between the charged and the neutral components of the plasma is mainly due to the ions. Thus, the Lorenz force i x B acts mainly on the electron component of the plasma, whereas the balancing gas pressure gradient and gravity terms act mainly on the neutral component.

The effect of a time harmonic-magnetic field on the stability of cylindrical ferrofluids in the presence of heat and mass transfer

1995 ◽  
Vol 73 (9-10) ◽  
pp. 595-601 ◽  
Author(s):  
Galal M. Moatimid
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Uniform Field ◽  
Periodic Field ◽  
Cylindrical Interface ◽  
Time Harmonic ◽  
General Dispersion ◽  
The Stability ◽  
Transition Curves

The stability of two ferrofluids separated by a cylindrical interface and pervaded by a time harmonic-magnetic field is considered. The magnetic fluids are sandwiched between two rigid cylindrical edges. The cylindrical interface allows heat and mass transfer. A general dispersion equation is obtained. Some previous studies are compared using appropriate data. The case of a uniform field has been studied before, the attention is thus focussed to the case of the periodic field. The transition curves are obtained by means of Whittaker's technique. The analytical results are confirmed numerically. It is found that heat and mass transfer and the frequency of the magnetic field have a destabilizing influence.

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