Excitation of high-frequency fluctuations by suprathermal electrons in a slowly varying magnetic field

1991 ◽  
Vol 34 (8) ◽  
pp. 710-712
Author(s):  
Yu. M. Rozenraukh
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Suprathermal Electrons ◽  
Frequency Fluctuations

Excitation of high-frequency waves with mixed polarization by streaming energetic electrons

1979 ◽  
Vol 22 (2) ◽  
pp. 277-288 ◽  
Author(s):  
L. C. Lee ◽  
C. S. Wu ◽  
H. P. Freund ◽  
D. Dillenburg ◽  
J. Goedert
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Plasma Frequency ◽  
Electron Plasma ◽  
Ion Dynamics ◽  
Electron Plasma Frequency ◽  
Ambient Magnetic Field ◽  
Suprathermal Electrons ◽  
High Frequency Waves ◽  
Thermal Background

The excitation of the slow extraordinary and electron whistler modes with frequencies in the vicinity of the electron plasma frequency is investigated for a plasma which is composed of thermal and suprathermal electrons. Ion dynamics are ignored. The suprathermal electrons are assumed to comprise a long, anisotropic tail parallel to the ambient magnetic field. Instability is found to occur via a relativistic, anomalous gyroresonance with the suprathermal electrons, and to excite waves with frequencies above and below the electron plasma frequency. Landau and cyclotron damping due to the thermal background is included in the treatment.

Origin of quasi-harmonic emission bands with fine structure in the dynamic spectra of high-frequency interpulses of the Crab pulsar

2020 ◽  
Vol 495 (4) ◽  
pp. 3715-3721
Author(s):  
V V Zheleznyakov ◽  
V E Shaposhnikov
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
Current Sheet ◽  
High Frequency ◽  
Neutral Current ◽  
Transverse Magnetic ◽  
Central Plane ◽  
Harmonic Emission ◽  
Radiation Spectra ◽  
Suprathermal Electrons

ABSTRACT We study the origin of quasi-harmonic emission bands with fine structure observed in the dynamic radiation spectra of high-frequency interpulses. The possible explanation of observed structure is based on the effect of double plasma resonance (DPR) at electron cyclotron harmonics realized in the magnetosphere of pulsar in a local radio emission source filled with non-relativistic plasma. The model of the source consists of neutral current sheet with a transverse magnetic field where plasma waves are generated due to DPR effect. It is shown that the emergence of emission bands and their frequency spacing are due to the inhomogeneity of the plasma and magnetic field along the current sheet, and their fine structure is due to the inhomogeneity of the current sheet in the direction orthogonal to it. Each quasi-harmonic emission band represents a system of elements of fine features of radiation that is generated by suprathermal electrons under DPR conditions. The observed upward drift of quasi-harmonic emission bands is due to the displacement of suprathermal electrons across the current sheet and an increase in the DPR frequencies with distance from the central plane of the layer.

scholarly journals Studies about the design of magnetic bionanocomposite

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Robert Müller ◽  
Janna Kuchinka ◽  
Thomas Heinze
Keyword(s):  
Magnetic Field ◽  
Drug Delivery ◽  
Mössbauer Spectroscopy ◽  
Fatty Acid ◽  
Optical Microscopy ◽  
High Frequency ◽  
Mossbauer Spectroscopy ◽  
Fatty Acid Esters ◽  
Iron Oxide Particles ◽  
Mößbauer Spectroscopy

Abstract Magnetic nanocomposites are a class of smart materials that have attracted recent interest as drug delivery systems or as medical implants. A new approach toward the biocompatible nanocomposites suitable for remote melting is presented. It is shown that magnetite nanoparticles (MNPs) can be embedded into a matrix of biocompatible thermoplastic dextran esters. For that purpose, fatty acid esters of dextran with adjustable melting points in the range of 30–140 °C were synthesized. Esterification of the polysaccharide by activation of the acid as iminium chlorides guaranteed mild reaction conditions leading to high-quality products as confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy as well as by gel permeation chromatography (GPC). A method for the preparation of magnetically responsive bionanocomposites (BNCs) was developed consisting of combined dissolution/suspension of the dextran ester and hydrophobized MNPs in an organic solvent followed by homogenization with ultrasonication, casting of the solution, drying and melting of the composite for a defined shaping. This process leads to a uniform distribution of MNPs in BNC as revealed by scanning electron microscope (SEM). Samples of different geometries were exposed to high-frequency alternating magnetic field (AMF). It could be shown that defined remote melting of such biocompatible nanocomposites is possible for the first time. This may lead to a new class of magnetic remote-control systems, which are suitable for controlled release applications or self-healing materials. BNCs containing biocompatible dextran fatty acid ester melting close to human body temperature were prepared and loaded with Rhodamine B (RhB) or green fluorescent protein (GFP) as model drugs to evaluate their potential use as drug delivery system. The release of the model drugs from the magnetic BNC investigated under the influence of a high-frequency AMF (20 kA/m at 400 kHz) showed that on-demand release is realized by applying the external AMF. The BNC possessed a long-term stability (28 d) of the incorporated iron oxide particles after incubation in artificial body fluids. Temperature-dependent mobility investigations of MNP in the molten BNC were carried out by optical microscopy, magnetometry, alternating current (AC) susceptibility, and Mössbauer spectroscopy measurements. Optical microscopy shows a movement of agglomerates and texturing in the micrometer scale, whereas AC susceptometry and Mössbauer spectroscopy investigations reveal that the particles perform diffusive Brownian motion in the liquid polymer melt as separated particles rather than as large agglomerates. Furthermore, a texturing of MNP in the polymer matrix by a static magnetic field gradient was investigated. First results on the preparation of cross-linkable dextran esters are shown. Cross-linking after irradiation of the BNC prevents melting that can be used to influence texturing procedures.

The behavior of TIG welding arc in a high-frequency axial magnetic field

2020 ◽  
Vol 65 (1) ◽  
pp. 95-104
Author(s):  
H. Wu ◽  
Y. L. Chang ◽  
Alexandr Babkin ◽  
Boyoung Lee
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Axial Magnetic Field ◽  
Tig Welding ◽  
Welding Arc

scholarly journals Non-Uniform Bridge Connection of a High-Frequency Carrier-Type Thin-Film Magnetic Field Sensor

1999 ◽  
Vol 23 (4_2) ◽  
pp. 1621-1624 ◽  
Author(s):  
M. Takezawa ◽  
H. Ohdaira ◽  
M. Baba ◽  
M. Yamaguchi ◽  
K. I. Arai ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
High Frequency ◽  
Magnetic Field Sensor ◽  
Field Sensor
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