Connecting magnetic fields from sub-galactic scale to clusters of galaxies and beyond with cosmological MHD simulations

AbstractUsing the MHD version of Gadget3 (Stasyszyn, Dolag & Beck 2013) and a model for the seeding of magnetic fields by supernovae (SN), we performed simulations of the evolution of the magnetic fields in galaxy clusters and study their effects on the heat transport within the intra cluster medium (ICM). This mechanism – where SN explosions during the assembly of galaxies provide magnetic seed fields – has been shown to reproduce the magnetic field in Milky Way-like galactic halos (Beck et al. 2013). The build up of the magnetic field at redshifts before z = 5 and the accordingly predicted rotation measure evolution are also in good agreement with current observations. Such magnetic fields present at high redshift are then transported out of the forming protogalaxies into the large-scale structure and pollute the ICM (in a similar fashion to metals transport). Here, complex velocity patterns, driven by the formation process of cosmic structures are further amplifying and distributing the magnetic fields. In galaxy clusters, the magnetic fields therefore get amplified to the observed μG level and produce the observed amplitude of rotation measures of several hundreds of rad/m2. We also demonstrate that heat conduction in such turbulent fields on average is equivalent to a suppression factor around 1/20th of the classical Spitzer value and in contrast to classical, isotropic heat transport leads to temperature structures within the ICM compatible with observations (Arth et al. 2014).

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Probing interstellar magnetic fields with Supernova remnants

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309030087 ◽

2008 ◽

Vol 4 (S259) ◽

pp. 75-80 ◽

Cited By ~ 2

Author(s):

Roland Kothes ◽

Jo-Anne Brown

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Supernova Remnants ◽

Large Scale ◽

Galactic Plane ◽

Field Configuration ◽

Large Scale Magnetic Field ◽

Rotation Measure ◽

Field Lines ◽

The Magnetic Field

AbstractAs Supernova remnants expand, their shock waves are freezing in and compressing the magnetic field lines they encounter; consequently we can use Supernova remnants as magnifying glasses for their ambient magnetic fields. We will describe a simple model to determine emission, polarization, and rotation measure characteristics of adiabatically expanding Supernova remnants and how we can exploit this model to gain information about the large scale magnetic field in our Galaxy. We will give two examples: The SNR DA530, which is located high above the Galactic plane, reveals information about the magnetic field in the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre of our Galaxy and reveals the most probable direction where the large-scale magnetic field is perpendicular to the line of sight. This may help to decide on the large-scale magnetic field configuration of our Galaxy. But more observations of SNRs are needed.

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An 84-μG Magnetic Field in a Galaxy at Z=0.692?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308027439 ◽

2008 ◽

Vol 4 (S254) ◽

pp. 95-96

Author(s):

Arthur M. Wolfe ◽

Regina A. Jorgenson ◽

Timothy Robishaw ◽

Carl Heiles ◽

Jason X. Prochaska

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Faraday Rotation ◽

Large Scale ◽

Dynamo Model ◽

Magnetic Field Generation ◽

Interstellar Gas ◽

Splitting Technique ◽

Average Value ◽

The Magnetic Field

AbstractThe magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and the formation of stars (Beck 2005). The field associated with ionized interstellar gas has been determined through observations of pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the rotation of the plane of linear polarization, i.e., Faraday rotation, yield an average value B ≈ 3 μG (Han et al. 2006). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars (Kronberg et al. 2008) suggests similar magnetic fields are present in foreground galaxies with redshifts z > 1. As Faraday rotation alone, however, determines neither the magnitude nor the redshift of the magnetic field, the strength of galactic magnetic fields at redshifts z > 0 remains uncertain.Here we report a measurement of a magnetic field of B ≈ 84 μG in a galaxy at z =0.692, using the same Zeeman-splitting technique that revealed an average value of B = 6 μG in the neutral interstellar gas of our Galaxy (Heiles et al. 2004). This is unexpected, as the leading theory of magnetic field generation, the mean-field dynamo model, predicts large-scale magnetic fields to be weaker in the past, rather than stronger (Parker 1970).The full text of this paper was published in Nature (Wolfe et al. 2008).

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No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽

10.3390/data6010004 ◽

2021 ◽

Vol 6 (1) ◽

pp. 4

Author(s):

Evgeny Mikhailov ◽

Daniela Boneva ◽

Maria Pashentseva

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Point Of View ◽

Accretion Discs ◽

Wide Range ◽

Astrophysical Objects ◽

Alpha Effect ◽

The Stability ◽

The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

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Decaying turbulence and magnetic fields in galaxy clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1918 ◽

2019 ◽

Vol 488 (3) ◽

pp. 3439-3445 ◽

Cited By ~ 1

Author(s):

Sharanya Sur

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Galaxy Clusters ◽

Power Law ◽

Dynamo Action ◽

Wide Range ◽

Major Merger ◽

Decaying Turbulence ◽

Field Decay ◽

The Magnetic Field

Abstract We explore the decay of turbulence and magnetic fields generated by fluctuation dynamo action in the context of galaxy clusters where such a decaying phase can occur in the aftermath of a major merger event. Using idealized numerical simulations that start from a kinetically dominated regime we focus on the decay of the steady state rms velocity and the magnetic field for a wide range of conditions that include varying the compressibility of the flow, the forcing wavenumber, and the magnetic Prandtl number. Irrespective of the compressibility of the flow, both the rms velocity and the rms magnetic field decay as a power law in time. In the subsonic case we find that the exponent of the power law is consistent with the −3/5 scaling reported in previous studies. However, in the transonic regime both the rms velocity and the magnetic field initially undergo rapid decay with an ≈t−1.1 scaling with time. This is followed by a phase of slow decay where the decay of the rms velocity exhibits an ≈−3/5 scaling in time, while the rms magnetic field scales as ≈−5/7. Furthermore, analysis of the Faraday rotation measure (RM) reveals that the Faraday RM also decays as a power law in time ≈t−5/7; steeper than the ∼t−2/5 scaling obtained in previous simulations of magnetic field decay in subsonic turbulence. Apart from galaxy clusters, our work can have potential implications in the study of magnetic fields in elliptical galaxies.

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Near-infrared Polarimetry and Interstellar Magnetic Fields in the Galactic Center

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314011569 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 387-387

Author(s):

S. Nishiyama ◽

H. Hatano ◽

T. Nagata ◽

M. Tamura

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Near Infrared ◽

Galactic Center ◽

Smooth Transition ◽

The Magnetic Field

AbstractWe present a large-scale view of the magnetic field (MF) in the central 3° × 2° region of our Galaxy. There is a smooth transition of the large-scale MF configuration in this region.

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Polarized radiative transfer, rotation measure fluctuations, and large-scale magnetic fields

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2683 ◽

2019 ◽

Vol 490 (2) ◽

pp. 1697-1713

Author(s):

Alvina Y L On ◽

Jennifer Y H Chan ◽

Kinwah Wu ◽

Curtis J Saxton ◽

Lidia van Driel-Gesztelyi

Keyword(s):

Magnetic Field ◽

Radiative Transfer ◽

Magnetic Fields ◽

Large Scale ◽

Longitudinal Direction ◽

Density Fluctuations ◽

Transport Processes ◽

Spatial Correlations ◽

Rotation Measure ◽

Radiative Transfer Equations

ABSTRACT Faraday rotation measure (RM) at radio wavelengths is commonly used to diagnose large-scale magnetic fields. It is argued that the length-scales on which magnetic fields vary in large-scale diffuse astrophysical media can be inferred from correlations in the observed RM. RM is a variable which can be derived from the polarized radiative transfer equations in restrictive conditions. This paper assesses the usage of rotation measure fluctuation (RMF) analyses for magnetic field diagnostics in the framework of polarized radiative transfer. We use models of various magnetic field configurations and electron density distributions to show how density fluctuations could affect the correlation length of the magnetic fields inferred from the conventional RMF analyses. We caution against interpretations of RMF analyses when a characteristic density is ill defined, e.g. in cases of lognormal-distributed and fractal-like density structures. As the spatial correlations are generally not the same in the line-of-sight longitudinal direction and the sky plane direction, one also needs to clarify the context of RMF when inferring from observational data. In complex situations, a covariant polarized radiative transfer calculation is essential to capture all aspects of radiative and transport processes, which would otherwise ambiguate the interpretations of magnetism in galaxy clusters and larger scale cosmological structures.

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Particle re-acceleration and Faraday-complex structures in the RXC J1314.4-2515 galaxy cluster

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2408 ◽

2019 ◽

Cited By ~ 1

Author(s):

C Stuardi ◽

A Bonafede ◽

D Wittor ◽

F Vazza ◽

A Botteon ◽

...

Keyword(s):

Magnetic Field ◽

Galaxy Clusters ◽

Galaxy Cluster ◽

Complex Structures ◽

Very Large Array ◽

Rotation Measure ◽

Low Levels ◽

Hydrodynamical Simulations ◽

Polarization Fraction ◽

The Magnetic Field

Abstract Radio relics are sites of electron (re)acceleration in merging galaxy clusters but the mechanism of acceleration and the topology of the magnetic field in and near relics are yet to be understood. We are carrying out an observational campaign on double relic galaxy clusters starting with RXC J1314.4-2515. With Jansky Very Large Array multi-configuration observations in the frequency range 1-4 GHz, we perform both spectral and polarization analyses, using the Rotation Measure synthesis technique. We use archival XMM-Newton observations to constrain the properties of the shocked region. We discover a possible connection between the activity of a radio galaxy and the emission of the eastern radio relic. In the northern elongated arc of the western radio relic, we detect polarized emission with an average polarization fraction of 31 % at 3 GHz and we derive the Mach number of the underlying X-ray shock. Our observations reveal low levels of fractional polarization and Faraday-complex structures in the southern region of the relic, which point to the presence of thermal gas and filamentary magnetic field morphology inside the radio emitting volume. We measured largely different Rotation Measure dispersion from the two relics. Finally, we use cosmological magneto-hydrodynamical simulations to constrain the magnetic field, viewing angle, and to derive the acceleration efficiency of the shock. We find that the polarization properties of RXC J1314.4-2515 are consistent with a radio relic observed at 70○ with respect to the line of sight and that efficient re-acceleration of fossil electrons has taken place.

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Solar Dynamo

Oxford Research Encyclopedia of Physics ◽

10.1093/acrefore/9780190871994.013.11 ◽

2020 ◽

Author(s):

Robert Cameron

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Flux ◽

Differential Rotation ◽

Large Scale ◽

Toroidal Field ◽

Solar Dynamo ◽

Small Scale ◽

The Sun ◽

The Magnetic Field

The solar dynamo is the action of flows inside the Sun to maintain its magnetic field against Ohmic decay. On small scales the magnetic field is seen at the solar surface as a ubiquitous “salt-and-pepper” disorganized field that may be generated directly by the turbulent convection. On large scales, the magnetic field is remarkably organized, with an 11-year activity cycle. During each cycle the field emerging in each hemisphere has a specific East–West alignment (known as Hale’s law) that alternates from cycle to cycle, and a statistical tendency for a North-South alignment (Joy’s law). The polar fields reverse sign during the period of maximum activity of each cycle. The relevant flows for the large-scale dynamo are those of convection, the bulk rotation of the Sun, and motions driven by magnetic fields, as well as flows produced by the interaction of these. Particularly important are the Sun’s large-scale differential rotation (for example, the equator rotates faster than the poles), and small-scale helical motions resulting from the Coriolis force acting on convective motions or on the motions associated with buoyantly rising magnetic flux. These two types of motions result in a magnetic cycle. In one phase of the cycle, differential rotation winds up a poloidal magnetic field to produce a toroidal field. Subsequently, helical motions are thought to bend the toroidal field to create new poloidal magnetic flux that reverses and replaces the poloidal field that was present at the start of the cycle. It is now clear that both small- and large-scale dynamo action are in principle possible, and the challenge is to understand which combination of flows and driving mechanisms are responsible for the time-dependent magnetic fields seen on the Sun.

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Methanol masers and magnetic field in IRAS18089-1732

Proceedings of the International Astronomical Union ◽

10.1017/s174392131701016x ◽

2017 ◽

Vol 13 (S336) ◽

pp. 285-286

Author(s):

Daria Dall’Olio ◽

W. H. T. Vlemmings ◽

G. Surcis ◽

H. Beuther ◽

B. Lankhaar ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

High Mass ◽

Small Scale ◽

Star Forming ◽

Large Scale Field ◽

The Impact ◽

Theoretical Simulations ◽

The Magnetic Field

AbstractTheoretical simulations have shown that magnetic fields play an important role in massive star formation: they can suppress fragmentation in the star forming cloud, enhance accretion via disc and regulate outflows and jets. However, models require specific magnetic configurations and need more observational constraints to properly test the impact of magnetic fields. We investigate the magnetic field structure of the massive protostar IRAS18089-1732, analysing 6.7 GHz CH3OH maser MERLIN observations. IRAS18089-1732 is a well studied high mass protostar, showing a hot core chemistry, an accretion disc and a bipolar outflow. An ordered magnetic field oriented around its disc has been detected from previous observations of polarised dust. This gives us the chance to investigate how the magnetic field at the small scale probed by masers relates to the large scale field probed by the dust.

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Evolution of a Filament/CH/Magnetic Field Complex

International Astronomical Union Colloquium ◽

10.1017/s0252921100047989 ◽

1998 ◽

Vol 167 ◽

pp. 393-396

Author(s):

B.A. Ioshpa ◽

E.I. Mogilevsky ◽

V.N. Obridko

Keyword(s):

Magnetic Field ◽

Active Region ◽

Magnetic Fields ◽

Large Scale ◽

Coronal Holes ◽

Field Structure ◽

Potential Approximation ◽

Magnetic Field Structure ◽

Single Complex ◽

The Magnetic Field

AbstractSOHO and YOHKOH images, as well as Hα filtergrams and magnetograms from IZMIRAN have been used to analyze the evolution of the related solar phenomena – filament, active region, and accompanying pair of coronal holes – during six solar rotations, with an emphasis on the events observed during August–September, 1996. The whole complex has been considered against the large–scale magnetic fields calculated under the potential approximation. A peculiar point has been found along the changing filament. It is shown that the phenomena under investigation (filament, active region, and coronal hole) form a single complex connected with the magnetic field structure.

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