scholarly journals Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
G. Revet ◽  
B. Khiar ◽  
E. Filippov ◽  
C. Argiroffi ◽  
J. Béard ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Magnetic Pressure ◽  
Astrophysical Jets ◽  
Jet Formation ◽  
Magnetic Nozzle ◽  
Jet Collimation ◽  
Changes Over Time ◽  
The Impact ◽  
The Magnetic Field

AbstractThe shaping of astrophysical outflows into bright, dense, and collimated jets due to magnetic pressure is here investigated using laboratory experiments. Here we look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun’s outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field.

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.

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.

scholarly journals The effects of magnetic field strength on the properties of wind generated from hot accretion flow

2018 ◽  
Vol 615 ◽  
pp. A35 ◽  
Author(s):  
De-Fu Bu ◽  
Amin Mosallanezhad
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Pressure Gradient ◽  
Magnetic Field Strength ◽  
Magnetic Pressure ◽  
Gas Pressure ◽  
Accretion Flow ◽  
Accretion Flows ◽  
Black Hole Accretion ◽  
The Magnetic Field

Context. Observations indicate that wind can be generated in hot accretion flow. Wind generated from weakly magnetized accretion flow has been studied. However, the properties of wind generated from strongly magnetized hot accretion flow have not been studied. Aims. In this paper, we study the properties of wind generated from both weakly and strongly magnetized accretion flow. We focus on how the magnetic field strength affects the wind properties. Methods. We solve steady-state two-dimensional magnetohydrodynamic equations of black hole accretion in the presence of a largescale magnetic field. We assume self-similarity in radial direction. The magnetic field is assumed to be evenly symmetric with the equatorial plane. Results. We find that wind exists in both weakly and strongly magnetized accretion flows. When the magnetic field is weak (magnetic pressure is more than two orders of magnitude smaller than gas pressure), wind is driven by gas pressure gradient and centrifugal forces. When the magnetic field is strong (magnetic pressure is slightly smaller than gas pressure), wind is driven by gas pressure gradient and magnetic pressure gradient forces. The power of wind in the strongly magnetized case is just slightly larger than that in the weakly magnetized case. The power of wind lies in a range PW ~ 10−4–10−3 Ṁinc2, with Ṁin and c being mass inflow rate and speed of light, respectively. The possible role of wind in active galactic nuclei feedback is briefly discussed.

Localization of the magnetic field in a plasma flow in laboratory simulations of astrophysical jets at the KPF-4-PHOENIX installation

2017 ◽  
Vol 61 (9) ◽  
pp. 775-782 ◽  
Author(s):  
K. N. Mitrofanov ◽  
S. S. Anan’ev ◽  
D. A. Voitenko ◽  
V. I. Krauz ◽  
G. I. Astapenko ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Flow ◽  
Astrophysical Jets ◽  
Laboratory Simulations ◽  
The Magnetic Field

scholarly journals Lepton-driven Nonresonant Streaming Instability

2021 ◽  
Vol 923 (2) ◽  
pp. 208
Author(s):  
Siddhartha Gupta ◽  
Damiano Caprioli ◽  
Colby C. Haggerty
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Magnetized Plasma ◽  
Ion Current ◽  
Pulsar Wind Nebulae ◽  
Particle In Cell ◽  
Streaming Instability ◽  
Electrons And Positrons ◽  
Pulsar Wind ◽  
The Magnetic Field

Abstract A strong super-Alfvénic drift of energetic particles (or cosmic rays) in a magnetized plasma can amplify the magnetic field significantly through nonresonant streaming instability (NRSI). While the traditional analysis is done for an ion current, here we use kinetic particle-in-cell simulations to study how the NRSI behaves when it is driven by electrons or by a mixture of electrons and positrons. In particular, we characterize the growth rate, spectrum, and helicity of the unstable modes, as well the level of the magnetic field at saturation. Our results are potentially relevant for several space/astrophysical environments (e.g., electron strahl in the solar wind, at oblique nonrelativistic shocks, around pulsar wind nebulae), and also in laboratory experiments.

Uticaj armirano betonskog stuba na raspodelu magnetskog polja mešovitog voda

2020 ◽  
Vol 22 (1-2) ◽  
pp. 58-64
Author(s):  
Teodora Gavrilov ◽  
◽  
Karolina Kasaš-Lažetić ◽  
Kristian Haška ◽  
Miroslav Prša
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Magnetic Field Distribution ◽  
Magnetic Flux Density ◽  
Reinforcing Bars ◽  
Magnitude Distribution ◽  
Calculation Results ◽  
Mixed Power ◽  
The Impact ◽  
The Magnetic Field

In this paper, the analysis of magnetic field distribution of overhead mixed power line (20 kV/0.4 kV) supported by reinforced concrete towers, named MNL-12 is presented. The impact of ferromagnetic, conductive parts of the pylons (reinforcing bars, billets and cross arm beams) on magnetic field distribution is investigated. The numerical calculations were performed in COMSOL Multiphysics program package on simplified 2D model. The main goal of the calculations was to examine the impact of currents induced in ferromagnetic conductive parts on magnetic field produced by currents in the power system’s conductors. The calculation results are presented graphically, as the diagrams of the magnetic flux density magnitude distribution in the tower plan, normal to the system’s axe. The calculation results demonstrated that the magnetic field of induced currents decreases the magnetic field produced by the currents of overhead power system.

Abstract 14497: Mri Effects on Pacemaker/ICD Within the Magnetic Field; An Intra-observer Variability Study

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Robert W Biederman ◽  
Loretta Gevenosky ◽  
Geetha Rayarao ◽  
RONALD WILLIAMS ◽  
Richard Lombardi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Field ◽  
Meaningful Use ◽  
Observer Variability ◽  
Intrinsic Variability ◽  
Mri Scan ◽  
Clinical Routine ◽  
The Impact ◽  
Variability Study ◽  
The Magnetic Field

Introduction: The evolution of pacemaker/ICD safety in the magnetic field has triggered considerable interest in more clinical routine use. However, many limitations to widespread adoption of this seemingly implausible idea just a few years ago remain: unresolved impact of the high magnetic field, RF amplitude and oscillatory forces on electronics with possible high field damage to capacitor, solenoid and microcircuitry. However, given recent vender refinements over the last 10 years, we hypothesized that the impact on such circuitry may be far less than expected. Method: Consecutive interrogation of 940 pts who underwent clinically indicated MRI were evaluated over 5 years. This cohort was comprised of neuro/neurosurgical (72%), orthopedic (11%) and cardiac (17%) cases. Routine interrogation was performed within 10 min of entry into the bore of a dedicated Cardiac MRI (GE, 1.5T, WI). As well, reinterrogation was performed within 10 min of departure MRI (average 21±12min). At the time of interrogation pre and post MRI, a separate, repeat interrogation was performed within 5 min of each other such that 2 sets of PM/ICD parameters were obtained pre and post MRI. Result: No complications to either pt or device occurred during the MRI comprising 564 PMs and 376 ICDs. A cardiologist was present guiding the interrogation, configuration, and reconfiguration of the PM/ICD as well was present for entire MRI. There were no significant differences in common clinical parameters. More importantly, there was no difference in any parameter when compared in any order pre to post MRI scan. See Table. Conclusion: Intrinsic variability and inherent changes triggered by MRI environments are clinically insignificant and statistically negligible thereby removing yet another of the last remaining fears and apprehensions for primary PM/ICD failure and destruction as we move towards a more uniform acceptance of this technology for clinically meaningful use, dissemination and acceptance.

scholarly journals The Impact of Sinusoidal Surface Temperature on the Natural Convective Flow of a Ferrofluid along a Vertical Plate

Mathematics ◽  
2019 ◽  
Vol 7 (11) ◽  
pp. 1014 ◽  
Author(s):  
Essam R. EL-Zahar ◽  
Ahmed M. Rashad ◽  
Laila F. Seddek
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Surface Temperature ◽  
Drag Coefficient ◽  
Volume Fraction ◽  
Differential Quadrature Method ◽  
Grid Points ◽  
The Impact ◽  
Sinusoidal Surface ◽  
The Magnetic Field

The spotlight of this investigation is primarily the effectiveness of the magnetic field on the natural convective for a Fe3O4 ferrofluid flow over a vertical radiate plate using streamwise sinusoidal variation in surface temperature. The energy equation is reduplicated by interpolating the non-linear radiation effectiveness. The original equations describing the ferrofluid motion and energy are converted into non-dimensional equations and solved numerically using a new hybrid linearization-differential quadrature method (HLDQM). HLDQM is a high order semi-analytical numerical method that results in analytical solutions in η -direction, and so the solutions are valid overall in the η domain, not only at grid points. The dimensionless velocity and temperature curves are elaborated. Furthermore, the engineering curiosity of the drag coefficient and local Nusselt number are debated and sketched in view of various emerging parameters. The analyzed numerical results display that applying the magnetic field to the ferroliquid generates a dragging force that diminishes the ferrofluid velocity, whereas it is found to boost the temperature curves. Furthermore, the drag coefficient sufficiently minifies, while an evolution in the heat transfer rate occurs as nanoparticle volume fraction builds. Additionally, the augmentation in temperature ratio parameter signifies a considerable growth in the drag coefficient and Nusselt number. The current theoretical investigation may be beneficial in manufacturing processes, development of transport of energy, and heat resources.

scholarly journals Mathematical Theory of Cylindrical Isothermal Blast Waves in a Magnetic Field

1981 ◽  
Vol 34 (3) ◽  
pp. 279 ◽  
Author(s):  
I Lerche
Keyword(s):  
Magnetic Field ◽  
Supernova Remnants ◽  
Magnetic Pressure ◽  
Blast Waves ◽  
Physical Domain ◽  
Fluid Flow Velocity ◽  
Magnetic Tension ◽  
Self Similar ◽  
The Magnetic Field ◽  
Similar Flows

An investigation is made of the self-similar flow behind a cylindrical blast wave from a line explosion (situated on r = 0, using conventional cylindrical coordinates r, 4>, z) in a medium whose density and magnetic field both vary as r -w ahead of the blast front, with the assumption that the flow is isothermal. The magnetic field can have components in both the azimuthal B(jJ and longitudinal B, directions. It is found that: (i) For B(jJ =f:. 0 =f:. B, a continuous single-valued solution with a velocity field representing outflow of material away from the line of explosion does not exist for OJ OJ > 0 the governing equation possesses a set of movable critical points. In this case it is shown that the fluid flow velocity is bracketed between two curves and that the asymptotes of the velocity curve on the shock are intersected by, or are tangent to, the two curves. Thus a solution always exists in the physical domain r ~ o. The overall conclusion from the investigation is that the behaviour of isothermal blast waves in the presence of an ambient magnetic field differs substantially from the behaviour calculated for no magnetic field. These results have an impact upon previous applications of the theory of self-similar flows to evolving supernova remnants without allowance for the dynamical influence of magnetic pressure and magnetic tension.

Why only a small fraction of quasars are radio loud?

2018 ◽  
Vol 14 (S342) ◽  
pp. 201-204
Author(s):  
Xinwu Cao
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Angular Momentum ◽  
Angular Velocity ◽  
Strong Magnetic Field ◽  
Weak Magnetic Field ◽  
Thin Disk ◽  
Relativistic Jets ◽  
Jet Formation ◽  
The Magnetic Field

AbstractIt is still a mystery why only a small fraction of quasars contain relativistic jets. A strong magnetic field is a necessary ingredient for jet formation. Gas falls from the Bondi radius RB nearly freely to the circularization radius Rc, and a thin accretion disk is formed within Rc We suggest that the external weak magnetic field threading interstellar medium is substantially enhanced in this region, and the magnetic field at Rc can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at RB. In this case, the magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that lead to a significantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole, either by the Blandford-Payne or/and Blandford-Znajek mechanisms. If the angular velocity of the circumnuclear gas is low, the field advection in the thin disk is inefficient, and it will appear as a radio-quiet (RQ) quasar.

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