scholarly journals Evolution of magnetic fields in the IGM: kinetic MHD turbulence

2008 ◽  
Vol 4 (S259) ◽  
pp. 563-564
Author(s):  
Reinaldo S. de Lima ◽  
E. M. de Gouveia Dal Pino ◽  
A. Lazarian ◽  
D. Falceta-Gonçalves
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Larmor Frequency ◽  
Local Magnetic Field ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Mhd Simulations ◽  
Small Density ◽  
Forced Turbulence ◽  
Ion Collision

AbstractIn this work, we present 3D MHD simulations of non-helical, forced turbulence, with an anisotropic thermal pressure with respect to the orientation of the local magnetic field. Such anisotropy arises when the plasma is weakly collisional, i.e., when the Larmor frequency is much greater than the ion-ion collision frequency. In this Kinetic MHD regime (KMHD), there are instabilities that give rise to fast growing magnetic fluctuations in the smallest scales. The plasma that fills the intergalactic and intracluster media has small density (n ~ 10−3cm−3), hence the effects of these instabilities could be important in the turbulent amplification of the magnetic fields there. In order to study the KMHD turbulence, we have performed 3D numerical simulations employing a godunov-MHD code (e.g., Kowal, Lazarian & Beresnyak 2007; Falceta-Gonçalves, Lazarian & Kowal 2008). The power spectrum of the velocity and magnetic fields were calculated for two cases: when there is a pre-existing mean magnetic field, and when there is only an initial weak magnetic field.

scholarly journals Inverse Energy Cascade in Advanced MHD Turbulence (the RNG Method)

1993 ◽  
Vol 157 ◽  
pp. 255-261
Author(s):  
N. Kleeorin ◽  
I. Rogachevskii
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Magnetic Field Effect ◽  
Magnetic Reynolds Number ◽  
Energy Cascade ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Inverse Energy Cascade ◽  
Large Scale Magnetic Field

The nonlinear (in terms of the large-scale magnetic field) effect of the modification of the magnetic force by an advanced small-scale magnetohydrodynamic (MHD) turbulence is considered. The phenomenon is due to the generation of magnetic fluctuations at the expense of hydrodynamic pulsations. It results in a decrease of the elasticity of the large-scale magnetic field.The renormalization group (RNG) method was employed for the investigation of the MHD turbulence at the large magnetic Reynolds number. It was found that the level of the magnetic fluctuations can exceed that obtained from the equipartition assumption due to the inverse energy cascade in advanced MHD turbulence.This effect can excite an instability of the large-scale magnetic field due to the energy transfer from the small-scale turbulent pulsations. This instability is an example of the inverse energy cascade in advanced MHD turbulence. It may act as a mechanism for the large-scale magnetic ropes formation in the solar convective zone and spiral galaxies.

scholarly journals On the probability distribution function of small-scale interplanetary magnetic field fluctuations

2004 ◽  
Vol 22 (10) ◽  
pp. 3751-3769 ◽  
Author(s):  
R. Bruno ◽  
V. Carbone ◽  
L. Primavera ◽  
F. Malara ◽  
L. Sorriso-Valvo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Robust Statistics ◽  
Interplanetary Space ◽  
Parametric Instability ◽  
Field Vector ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
The One

Abstract. In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as: a) Do we really know how the magnetic field vector orientation fluctuates in space? b) What are the statistics followed by the orientation of the vector itself? c) Do the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence. In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

scholarly journals Dynamo in the Intra-Cluster Medium: Simulation of CGL-MHD Turbulent Dynamo

2010 ◽  
Vol 6 (S274) ◽  
pp. 482-484
Author(s):  
R. Santos-Lima ◽  
E. M. de Gouveia Dal Pino ◽  
A. Lazarian ◽  
G. Kowal ◽  
D. Falceta-Gonçalves
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Mhd Equations ◽  
Local Magnetic Field ◽  
Necessary Condition ◽  
Pressure Tensor ◽  
Adiabatic Evolution ◽  
Turbulent Dynamo ◽  
Kinetic Effects ◽  
Forced Turbulence

AbstractThe standard magnetohydrodynamic (MHD) description of the plasma in the hot, magnetized gas of the intra-cluster (ICM) medium is not adequate because it is weakly collisional. In such collisionless magnetized gas, the microscopic velocity distribution of the particles is not isotropic, giving rise to kinetic effects on the dynamical scales. These kinetic effects could be important in understanding the turbulence as well as the amplification and maintenance of the magnetic fields in the ICM. It is possible to formulate fluid models for collisonless or weakly collisional gas by introducing modifications in the MHD equations. These models are often referred as kinetic MHD (KMHD). Using a KMHD model based on the CGL-closure, which allows the adiabatic evolution of the two components of the pressure tensor (the parallel and perpendicular components with respect to the local magnetic field), we performed 3D numerical simulations of forced turbulence in order to study the amplification of an initially weak seed magnetic field. We found that the growth rate of the magnetic energy is comparable to that of the ordinary MHD turbulent dynamo, but the magnetic energy saturates in a level smaller than that of the MHD case. We also found that a necessary condition for the dynamo to operate is to impose constraints on the anisotropy of the pressure.

scholarly journals Measuring Magnetic Fields from Water Masers Associated with a Synchrotron Protostellar Jet

2017 ◽  
Vol 13 (S336) ◽  
pp. 215-218
Author(s):  
Ciriaco Goddi ◽  
Gabriele Surcis
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Zeeman Splitting ◽  
High Mass ◽  
Local Magnetic Field ◽  
Mass Star ◽  
Dominant Component ◽  
Field Lines ◽  
Water Masers ◽  
The Magnetic Field

AbstractThe Turner-Welch Object in the W3(OH) high-mass star forming complex drives a synchrotron jet, which is quite exceptional for a high-mass protostar, and is associated with a strongly polarized water maser source, W3(H2O), making it an optimal target to investigate the role of magnetic fields on the innermost scales of protostellar disk-jet systems. We report here full polarimetric VLBA observations of water masers. The linearly polarized emission from water masers provides clues on the orientation of the local magnetic field, while the measurement of the Zeeman splitting from circular polarization provides its strength. By combining the information on the measured orientation and strength of the magnetic field with the knowledge of the maser velocities, we infer that the magnetic field evolves from having a dominant component parallel to the outflow velocity in the pre-shock gas (with field strengths of the order of a few tens of mG), to being mainly dominated by the perpendicular component (of order of a few hundred of mG) in the post-shock gas where the water masers are excited. The general implication is that in the undisturbed (i.e. not-shocked) circumstellar gas, the flow velocities would follow closely the magnetic field lines, while in the shocked gas the magnetic field would be re-configured to be parallel to the shock front as a consequence of gas compression.

The Aharanov-Bohm Phase Shift and Magnetic Vector Potential “A” Could Accommodate for Optical Coupler, Digital-to-Analogue Magnetic Field Excess Correlations of Photon Emissions Within Living Aqueous Systems

2016 ◽  
pp. 3333-3340
Author(s):  
Michael A Persinger ◽  
Stanley A Koren
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Photon ◽  
Rest Mass ◽  
Radioactive Decay ◽  
Local Magnetic Field ◽  
Magnetic Vector Potential ◽  
Aqueous Systems ◽  
Magnetic Field Effects ◽  
Rotating Magnetic Fields

Quantitative convergence for solutions involving electron drift velocity, the magnetic A vector and phase shifts reveal an increment of energy in the range of 10-20 J that could relate the Aharanov-Bohm phase modulation of the orbital frequency of a Bohr atom to the electron’s Compton wavelength. The universal persistence of 10-12 W per m2 whose energy applied the square of the hydrogen wavelength solves for the energy equivalence of the rest mass of an electron could set the conditions for excess correlations between electronic systems that produce magnetic fields through optocouplers. Experimental evidence and quantitative solutions indicate variations of the Lorentz Lemma and circularly rotating magnetic fields whose phase and group velocities are uncoupled could create the conditions for excess correlations. Modification of Basharov’s operator of resonance interaction for decoherence and entanglement in the radioactive decay of a diatomic system and Das and Misra’s estimates for the fractal charge of a photon strongly suggests that the efficacy for optocoupler circuits to generate non-local magnetic field effects in living and non-living aqueous systems originates from a single photon wave across the circuit’s p-n junctions. A review of the concepts and data indicate that excess correlations involving photons under optimal conditions are measureable within macrosystems

scholarly journals On MHD rotational transport, instabilities and dynamo action in stellar radiation zones

2008 ◽  
Vol 4 (S259) ◽  
pp. 421-422
Author(s):  
Stéphane Mathis ◽  
A.-S. Brun ◽  
J.-P. Zahn
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
High Resolution ◽  
Magnetic Fields ◽  
Transport Processes ◽  
Dynamo Action ◽  
Mhd Instability ◽  
Mhd Simulations ◽  
Stellar Radiation ◽  
Magnetic Transport

AbstractMagnetic field and their related dynamical effects are thought to be important in stellar radiation zones. For instance, it has been suggested that a dynamo, sustained by a m = 1 MHD instability of toroidal magnetic fields (discovered by Tayler in 1973), could lead to a strong transport of angular momentum and of chemicals in such stable regions. We wish here to recall the different magnetic transport processes present in radiative zone and show how the dynamo can operate by recalling the conditions required to close the dynamo loop (BPol → BTor → BPol). Helped by high-resolution 3D MHD simulations using the ASH code in the solar case, we confirm the existence of the m = 1 instability, study its non-linear saturation, but we do not detect, up to a magnetic Reylnods number of 105, any dynamo action.

Statistical tracing of turbulent magnetic fields in the optically thick interstellar medium

2021 ◽  
Author(s):  
Bo Yang ◽  
Jian-Fu Zhang ◽  
Alex Lazarian ◽  
José Renan de Medeiros
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Interstellar Medium ◽  
Principal Component ◽  
Mhd Turbulence ◽  
3D Data ◽  
Gradient Technique ◽  
The Magnetic Field ◽  
Good Agreement

Abstract Based on high-resolution 3D data cubes from Magnetohydrodynamic (MHD) turbulence simulation, we study how to reveal the direction of the magnetic field within the optically thick interstellar medium by using the Velocity Gradient Technique (VGT), the Correlation Function Anisotropy (CFA), and Principal Component Analysis of Anisotropies (PCAA). Considering the CO molecular tracers as a tracing method for radiative transfer processes, we find that the VGT and CFA can successfully trace the orientation of mean magnetic fields, which is in good agreement with the low-resolution numerical results obtained in the case of the optically thin medium. Similar to the simulation of optically thin ISM, our simulations show that PCCA is still unusable in optically thick media. The synergetic application of VGT and CFA to high-resolution spectroscopic observations is expected to yield more valuable information on the interstellar magnetic field.

scholarly journals Magnetic fields in limb solar flares on heights 2–14 Mm

2020 ◽  
pp. 6-14
Author(s):  
V. Lozitsky ◽  
I. Yakovkin ◽  
E. Kravchenko
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Flares ◽  
Zeeman Splitting ◽  
Local Magnetic Field ◽  
Echelle Spectrograph ◽  
Superstrong Magnetic Field ◽  
National University ◽  
Field Lines ◽  
The Magnetic Field

We present the results of observations of two powerful limb solar flares which occured on 17 July 1981 and 14 July 2005. Spectral observations of these flares were carried out with the Echelle spectrograph of the Horizontal Solar Telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. In order to measure the magnetic fields in these flares, I ± V profiles of К СаІІ, HeI 4471.5 and Нα lines were studied. It was found that effective (averaged) magnetic field Вeff in the flares reached 1100–3000 G on heights 2–14 Mm. However, the spectral evidences to yet stronger fields of ~ 104 G range were found. In particular, the weak spectral evidences of large Zeeman splitting were found in first flare by HeI 4471.5 line; this evidences corresponds to superstrong magnetic field of 15.5 kG. In the second flare, Нα line has non-parallelism of bisectors of I ± V profiles which can reflect existence of 1550–3000 G fields in the flare. However, in frame of simple two-component model these observed values can correspond to true local (amplitude) magnetic fields Вmax in range 4.65–18 kG. Apparently, such superstrong magnetic fields arise in structures of a force-free type, with strong twisting of the field lines. It is precisely such field values that are necessary in solar flares for energy reasons. Indeed, solar flares emit energy in the range of 1027-1032 erg in a volume of the order of 1027 cm3. Elementary calculations show that in order to provide such energy in such a volume, the magnetic field strength should be at least 103 G. In addition, if we take into account that solar magnetic fields have the sub-telescopic (spatially unresolved) structure, then the local magnetic field intensities in the flares at the coronal level can be expected even higher.

scholarly journals Geometry of Magnetic Fluctuations near the Sun from the Parker Solar Probe

2021 ◽  
Vol 923 (2) ◽  
pp. 193
Author(s):  
R. Bandyopadhyay ◽  
D. J. McComas
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Inertial Range ◽  
Local Magnetic Field ◽  
The Sun ◽  
Magnetic Fluctuations ◽  
Outer Scale ◽  
Degree Of Anisotropy ◽  
Dissipation Range

Abstract Solar wind magnetic fluctuations exhibit anisotropy due to the presence of a mean magnetic field in the form of the Parker spiral. Close to the Sun, direct measurements were not available until the recently launched Parker Solar Probe (PSP) mission. The nature of the anisotropy and geometry of the magnetic fluctuations play a fundamental role in dissipation processes and in the transport of energetic particles in space. Using PSP data, we present measurements of the geometry and anisotropy of the inner heliosphere magnetic fluctuations, from fluid to kinetic scales. The results are surprising and different from 1 au observations. We find that fluctuations evolve characteristically with size scale. However, unlike 1 au solar wind, at the outer scale, the fluctuations are dominated by wavevectors quasi-parallel to the local magnetic field. In the inertial range, average wavevectors become less field aligned, but still remain more field aligned than near-Earth solar wind. In the dissipation range, the wavevectors become almost perpendicular to the local magnetic field in the dissipation range, to a much higher degree than those indicated by 1 au observations. We propose that this reduced degree of anisotropy in the outer scale and inertial range is due to the nature of large-scale forcing outside the solar corona.

scholarly journals Radiation-MHD Simulations of HII Region Expansion in Turbulent Molecular Clouds

2010 ◽  
Vol 6 (S270) ◽  
pp. 297-300
Author(s):  
S. J. Arthur ◽  
W. J. Henney ◽  
G. Mellema ◽  
F. de Colle ◽  
E. Vázquez-Semadeni
Keyword(s):  
Magnetic Field ◽  
Initial Conditions ◽  
Turbulent Medium ◽  
Molecular Gas ◽  
Mhd Turbulence ◽  
Hii Region ◽  
Mhd Simulations ◽  
Main Effect ◽  
Uniform Medium ◽  
The Magnetic Field

AbstractWe use numerical simulations to investigate how the expansion of an HII region is affected by an ambient magnetic field. First we consider the test problem of expansion in a uniform medium with a unidirectional magnetic field. We then describe the expansion of an HII region in a turbulent medium, taking as our initial conditions the results of and MHD turbulence simulation. We find that although in the uniform medium case the magnetic field does produce interesting effects over long length and timescales, in the turbulent medium case the main effect of the magnetic field is to reduce the efficiency of fragmentation of the molecular gas.

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