scholarly journals Impact of the ISM magnetic field on GRB afterglow polarization

2021 ◽  
Author(s):  
O Teboul ◽  
N J Shaviv
Keyword(s):  
Magnetic Field ◽  
Random Field ◽  
Polarization Angle ◽  
Random Component ◽  
Upper Limit ◽  
Forward Shock ◽  
Random Components ◽  
Post Shock ◽  
The Impact ◽  
Short Grbs

Abstract Linear polarization has been measured in several GRB afterglows. After a few days, polarization arises from the forward shock emission which depends on the post-shock magnetic field. The latter can originate both from compression of existing fields, here the ISM magnetic field, and from shock generated instabilities. For short GRBs, previous modelling of the polarization arising from the forward shock considered a random field fully or partially confined to the shock plane. However, the ISM magnetic field likely consists of both random and ordered components. Here we study the impact of a more realistic magnetic field having both ordered and random components. We present our semi-analytical model and compute polarization curves arising for different magnetic field configurations. We find that the presence of an ordered component, even significantly weaker than the random one, has distinct signatures that could be detectable. In the presence of an ordered component not in the observer plane, we show that: i) for an observer inside the jet, the polarization angle θp either remains constant during all the afterglow phase or exhibits variations smaller than the 90○ swing expected from a random component solely, ii) for an off-axis observer, the polarization angle evolves from $\theta _p^{\max }$, before the jet break to its opposite after the jet break. We also find that the upper limit polarization for GRB170817 requires a random field not fully confined to the shock plane and is compatible with an ordered component as large as half the random one.

scholarly journals Magnetic fields in supernova remnants from OH (1720 MHz) masers

2002 ◽  
Vol 206 ◽  
pp. 217-220 ◽  
Author(s):  
Crystal L. Brogan ◽  
Mark J. Claussen ◽  
William M. Goss
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Zeeman Splitting ◽  
Molecular Gas ◽  
Maser Spot ◽  
Maser Line ◽  
Post Shock ◽  
The Impact

Supernovae have a profound effect on the morphology, kinematics, and metallicity of galaxies. The impact of supernova shocks on surrounding molecular clouds is also thought to trigger new generations of star formation. A critical ingredient in such interactions and, indeed, all aspects of supernova remnant (SNR) evolution are magnetic fields. In recent years, OH (1720 MHz) masers have been used as signposts for the interaction of SNRs with molecular gas. In addition to tracing SNR/molecular cloud interactions, the OH (1720 MHz) maser line also provides a unique opportunity to measure the strength of the post-shock magnetic field via Zeeman splitting. Recent results from efforts to both detect the magnetic fields and resolve the maser spot sizes of OH (1720 MHz) masers toward W51C using the VLBA and W44 using MERLIN are presented. These observations have yielded magnetic field detections between 0.5 and 2.5 mG and large maser spot sizes of about 1015 cm.

MAGNETIC FIELD IMPACT UPON TRIBOTECHNICAL CHARACTERISTICS OF PERMANENT CONNECTIONS IN RELATION TO FRICTION SHOCK ABSORBERS

2020 ◽  
Vol 2020 (10) ◽  
pp. 4-11
Author(s):  
Victor Tikhomirov ◽  
Aleksandr Gorlenko ◽  
Stanislav Volohov ◽  
Mikhail Izmerov
Keyword(s):  
Magnetic Field ◽  
Friction Factor ◽  
Physical Contact ◽  
Active Centers ◽  
Press Fit ◽  
Electro Magnetic Field ◽  
Investigation Methods ◽  
Electro Magnetic ◽  
The Impact ◽  
The Magnetic Field

The work purpose is the investigation of magnetic field impact upon properties of friction steel surfaces at fit stripping with tightness through manifested effects and their wear visually observed. On the spots of a real contact the magnetic field increases active centers, their amount and saturation with the time of dislocation outlet, and has an influence upon tribo-mating. The external electro-magnetic field promotes the increase of the number of active centers at the expense of dislocations outlet on the contact surface, and the increase of a physical contact area results in friction tie strengthening and growth of a friction factor. By the example of friction pairs of a spentonly unit in the suspension of coach cars there is given a substantiation of actuality and possibility for the creation of technical devices with the controlled factor of friction and the stability of effects achieved is also confirmed experimentally. Investigation methods: the fulfillment of laboratory physical experiments on the laboratory plant developed and patented on bush-rod samples inserted with the fit and tightness. The results of investigations and novelty: the impact of the magnetic field upon the value of a stripping force of a press fit with the guaranteed tightness is defined. Conclusion: there is a possibility to control a friction factor through the magnetic field impact upon a friction contact.

THE IMPACT OF A MAGNETIC FIELD ON THE WEAR OF THE GRINDING BODIES, LINING, AND ORE DISINTEGRATION (IN ENGLISH)

2018 ◽  
pp. 75-82
Author(s):  
KHOPUNOV EDUARD AFANAS'EVICH ◽  
◽  
SHATAILOV IURII LEONIDOVICH ◽  
VORONCHIKHIN SERGEI LEONIDOVICH ◽  
SHATAILOV ALEKSANDR IUR'EVICH ◽  
...  
Keyword(s):  
Magnetic Field ◽  
The Impact

scholarly journals Qualitative and quantitative assessment of magnetic vestibular stimulation in humans

2020 ◽  
Vol 30 (6) ◽  
pp. 353-361
Author(s):  
Rebecca S. Dewey ◽  
Rachel Gomez ◽  
Chris Degg ◽  
David M. Baguley ◽  
Paul M. Glover
Keyword(s):  
Magnetic Field ◽  
Objective Measure ◽  
Quantitative Measure ◽  
Vestibular Stimulation ◽  
Initial Study ◽  
Clinical Test ◽  
Healthy Control ◽  
Student’S T ◽  
The Impact ◽  
The Magnetic Field

The sensation of phantom motion or exhibition of bodily sway is often reported in the proximity of an MR scanner. It is proposed that the magnetic field stimulates the vestibular system. There are a number of possible mechanisms responsible, and the relative contributions of susceptibility on the otolithic receptors and the Lorentz force on the cupulae have not yet been explored. This exploratory study aims to investigate the impact of being in the proximity of a 7.0 T MR scanner. The modified clinical test of sensory interaction on balance (mCTSIB) was used to qualitatively ascertain whether or not healthy control subjects who passed the mCTSIB in normal conditions 1) experienced subjective sensations of dizziness, vertigo or of leaning or shifting in gravity when in the magnetic field and 2) exhibited visibly increased bodily sway whilst in the magnetic field compared to outside the magnetic field. Condition IV of the mCTSIB was video recorded outside and inside the magnetic field, providing a semi-quantitative measure of sway. For condition IV of the mCTSIB (visual and proprioceptive cues compromised), all seven locations/orientations around the scanner yielded significantly more sway than at baseline (p < 0.01 FDR). A Student’s t-test comparing the RMS velocity of a motion marker on the upper arm during mCTSIB condition IV showed a significant increase in the amount of motion exhibited in the field (T = 2.59; d.f. = 9; p = 0.029) compared to outside the field. This initial study using qualitative measures of sway demonstrates that there is evidence for MR-naïve individuals exhibiting greater sway while performing the mCTSIB in the magnetic field compared to outside the field. Directional polarity of sway was not significant. Future studies of vestibular stimulation by magnetic fields would benefit from the development of a sensitive, objective measure of balance function, which can be performed inside a magnetic field.

Synchronized periodic maser flares of multiple OH and CH3OH lines in G323.459–0.079

2021 ◽  
Vol 502 (4) ◽  
pp. 5658-5667
Author(s):  
G C MacLeod ◽  
Derck P Smits ◽  
J A Green ◽  
S P van den Heever
Keyword(s):  
Magnetic Field ◽  
Excited State ◽  
Central Region ◽  
Time Lags ◽  
Field Reversal ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Upper Limit ◽  
Methanol Masers ◽  
Magnetic Field Reversal

ABSTRACT The first confirmed periodically varying 6.031 and 6.035 GHz hydroxyl masers are reported here. They vary contemporaneously with the 6.7 GHz methanol masers in G323.459–0.079. The 1.665 GHz hydroxyl and 12.2  GHz methanol masers associated with G323.459–0.079 are also periodic. Evidence for periodicity is seen in all features in all transitions save a single 1.665 GHz hydroxyl maser feature. Historical excited-state hydroxyl maser observations set a stricter upper limit on the epoch in which a significant accretion event occurred. The associated burst in 6.7 GHz methanol maser activity has subsided significantly while the hydroxyl transitions are brightening possibly the result of changing physical conditions in the masing cloudlets. Time lags in methanol are confirmed and may be the result of the periodic flaring propagating outward from the central region of maser activity. A possible magnetic field reversal occurred during the accretion event.

Influence of rotating magnetic field on Maxwell saturated ferrofluid flow over a heated stretching sheet with heat generation/absorption

2019 ◽  
Vol 20 (5) ◽  
pp. 502 ◽  
Author(s):  
Aaqib Majeed ◽  
Ahmed Zeeshan ◽  
Farzan Majeed Noori ◽  
Usman Masud
Keyword(s):  
Magnetic Field ◽  
Temperature Field ◽  
Velocity Field ◽  
Differential Equations ◽  
Heat Transport ◽  
Viscous Dissipation ◽  
Heat Generation ◽  
Fluid Motion ◽  
Numerical Procedure ◽  
The Impact

This article is focused on Maxwell ferromagnetic fluid and heat transport characteristics under the impact of magnetic field generated due to dipole field. The viscous dissipation and heat generation/absorption are also taken into account. Flow here is instigated by linearly stretchable surface, which is assumed to be permeable. Also description of magneto-thermo-mechanical (ferrohydrodynamic) interaction elaborates the fluid motion as compared to hydrodynamic case. Problem is modeled using continuity, momentum and heat transport equation. To implement the numerical procedure, firstly we transform the partial differential equations (PDEs) into ordinary differential equations (ODEs) by applying similarity approach, secondly resulting boundary value problem (BVP) is transformed into an initial value problem (IVP). Then resulting set of non-linear differentials equations is solved computationally with the aid of Runge–Kutta scheme with shooting algorithm using MATLAB. The flow situation is carried out by considering the influence of pertinent parameters namely ferro-hydrodynamic interaction parameter, Maxwell parameter, suction/injection and viscous dissipation on flow velocity field, temperature field, friction factor and heat transfer rate are deliberated via graphs. The present numerical values are associated with those available previously in the open literature for Newtonian fluid case (γ 1 = 0) to check the validity of the solution. It is inferred that interaction of magneto-thermo-mechanical is to slow down the fluid motion. We also witnessed that by considering the Maxwell and ferrohydrodynamic parameter there is decrement in velocity field whereas opposite behavior is noted for temperature field.

A Proposed Model for Stochastic Vibration Analysis of Gear Transmission Systems

1996 ◽  
Author(s):  
Y. Wang ◽  
W. Zhang
Keyword(s):  
Vibration Analysis ◽  
Linear Time ◽  
Simulation System ◽  
Gear Transmission ◽  
Random Component ◽  
Transmission Systems ◽  
Transmission Errors ◽  
Proposed Model ◽  
Rotational Vibration ◽  
Random Components

Abstract A new mathematical model is presented for analyzing the vibration of gear transmission systems with consideration of the influence of the time-variant stiffness, loads, gear transmission errors. The gear transmission system is modeled as a non-linear, time-correlated and stationary stochastic system. The transmission errors of gears are decomposed into harmonic and random components in terms of the different characteristics of their spectrums. The random component is simulated by a second order Markov process. A simulation system for vibration analysis of gear transmission systems is then developed, based on this new model. The input to this system is a Guassian white noise process and harmonic errors, and the output is the rotational vibration acceleration of gears. Some experiments are conducted to verify the proposed model. By comparing the results generated from the simulation system with those from the experiments, the proposed model is found to reach a fairly good accuracy, and thus the model is useful in designing gear transmission systems with the objective to reduce the vibration and noise of the systems in operation.

Influence of the parameters of the gradient impact of a constant magnetic field on the intensification of the tobacco wilting process

2020 ◽  
Author(s):  
Е.И. Виневский ◽  
А.В. Чернов
Keyword(s):  
Magnetic Field ◽  
Constant Magnetic Field ◽  
Permanent Magnets ◽  
Moisture Loss ◽  
Duration Of Treatment ◽  
Linear Gradient ◽  
Tobacco Leaves ◽  
Tobacco Leaf ◽  
Gradient Effect ◽  
The Impact

Исследовано влияние параметров градиентного воздействия постоянного магнитного поля (ПМП) на интенсификацию процесса томления табачных листьев. Выдвинута рабочая гипотеза о том, что для стимулирования процесса томления листьев табака необходимо градиентное воздействие на них ПМП, возникающее в результате перемещения листьев относительно системы постоянных магнитов. Введено понятие приведенного коэффициента убыли влаги, равное отношению влажности обработанных листьев к влажности контрольных образцов – необработанных листьев. Установлено, что при использовании точечного градиентного воздействия ПМП на среднюю жилку табачных листьев частотой 0,3 Гц и продолжительности обработки в течение 115–125 с при высоте расположения магнитов 25 мм процесс томления листьев ускоряется на 28,8% в сравнении с контролем. При линейном градиентном воздействии ПМП на табачный лист с частотой 0,3 Гц процесс томления ускоряется на 4,7–15,5% в зависимости от продолжительности обработки (10–40 с). При увеличении продолжительности обработки до 80 с процесс томления листьев табака замедлился. Установлено максимальное ускорение процесса томления листьев табака: при точечном градиентном воздействии ПМП на среднюю жилку табачного листа частотой 0,3 Гц и продолжительности обработки в течение 115–125 с; при линейном градиентном воздействии ПМП на табачный лист частотой 0,3 Гц и продолжительности обработки в течение 55–65 с. The influence of the parameters of the gradient effect of a constant magnetic field (CMF) on the intensification of the process of languishing tobacco leaves is studied. A working hypothesis is put forward that to stimulate the process of tobacco languor, it is necessary to have a gradient effect on them of CMF, which occurs as a result of the movement of leaves relative to the system of permanent magnets. The concept of the reduced coefficient of moisture loss is introduced, which is equal to the ratio of the humidity of treated leaves to the humidity of control samples-untreated leaves. It was found that when using a point gradient effect of CMF on the middle vein of tobacco leaves with a frequency of 0,3 Hz and a duration of processing for 115–125 s at the height of the magnets of 25 mm, the process of leaf languor is accelerated by 28,8% in comparison with the control. When the linear gradient effect of CMF on the tobacco leaf with a frequency of 0,3 Hz, the languor process is accelerated by 4,7–15,5%, depending on the duration of treatment (10–40 s). In the future, with an increase in the processing time to 80 s, the process of languishing tobacco leaves slowed down. The maximum acceleration of the process of languishing tobacco leaves is established: for spot gradient effect of CMF on the mid-veins of tobacco leaf frequency of 0,3 Hz and duration of treatment for 115–125 s; a linear gradient in the impact of CMF on the tobacco sheet with a treatment frequency of 0,3 Hz and duration of treatment for 55–65 s.

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