Amplification of primordial magnetic fields by anisotropic gravitational collapse

King, E. J.; Coles, Peter

doi:10.1111/j.1365-2966.2005.09811.x

Cited by 11 publications

(11 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Additional to any dynamo action, further support for strong magnetic field amplification during the process of structure formation comes from the application of the Zel'dovich approximation (Zel'dovich 1970) to follow the MHD equations during the gravitational collapse (Bruni et al 2003;King and Coles 2006). These papers demonstrate the existence of a super-adiabatic amplification due to the anisotropy of the collapse of the LSS within the cold dark matter paradigm.…”

Section: Approximative Simulationsmentioning

confidence: 98%

Non-Thermal Processes in Cosmological Simulations

2008

View full text Add to dashboard Cite

Non-thermal components are key ingredients for understanding clusters of galaxies. In the hierarchical model of structure formation, shocks and large-scale turbulence are unavoidable in the cluster formation processes. Understanding the amplification and evolution of the magnetic field in galaxy clusters is necessary for modelling both the heat transport and the dissipative processes in the hot intra-cluster plasma. The acceleration, transport and interactions of non-thermal energetic particles are essential for modelling the observed emissions. Therefore, the inclusion of the non-thermal components will be mandatory for simulating accurately the global dynamical processes in clusters. In this review, we summarise the results obtained with the simulations of the formation of galaxy clusters which address the issues of shocks, magnetic field, cosmic ray particles and turbulence.

show abstract

Section: Approximative Simulationsmentioning

confidence: 98%

Non-Thermal Processes in Cosmological Simulations

2008

View full text Add to dashboard Cite

show abstract

“…As seen below, cooling also provides a sustained turbulent regime in the core and the corresponding additional field amplification. Based on the Zel'dovich approximation of gravitational dynamics, King & Coles (2006) predict that a cosmological magnetic field should evolve as a B ∝ ρ 0.87 , due to anisotropic collapse in a Gaussian random field. This compares favourably with the low-density part of our simulation (see Fig.…”

Section: Simulationsmentioning

confidence: 99%

Cosmological MHD simulation of a cooling flow cluster

Dubois¹,

Teyssier²

2008

A&A

107

134

View full text Add to dashboard Cite

Context. Various observations of magnetic fields in the intra-cluster medium (ICM), most of the time restricted to cluster cores, point towards a field strength of a few µG (synchrotron radiation from radio relics and radio halos, inverse Compton radiation in X-rays and Faraday rotation measure of polarised background sources). Both the origin and the spatial structure of galaxy cluster magnetic fields are still under debate. In particular, the radial profile of the magnetic field, from the core of clusters to their outskirts, is important for cosmic ray propagation within the cosmic web. Aims. In this letter, we highlight the importance of cooling processes in amplifying the magnetic field in the core of galaxy clusters up to one order of magnitude above the typical amplification obtained for a purely adiabatic evolution. Methods. We performed a "zoom" cosmological simulation of a 3 keV cluster, including dark matter and gas dynamics, atomic cooling, UV heating, and star formation using the newly developed MHD solver in the AMR code RAMSES. Results. Magnetic field amplification proceeds mainly through gravitational contraction. Shearing motions due to turbulence provide additional amplification in the outskirts of the cluster, while magnetic reconnection during mergers causes magnetic field dissipation in the core. Conclusions. Cooling processes have a strong impact on the magnetic field structure in the cluster. First, due to the sharp rise of the gas density in the centre, gravitational amplification is significantly higher, when compared to the non-radiative run. Second, cooling processes cause shearing motions to be much stronger in the core than in the adiabatic case, leading to additional field amplification and no significant magnetic reconnection. Cooling processes are therefore essential for determining the magnetic field profile in galaxy clusters.

show abstract

“…More detailed numerical studies have found that in realistic large‐scale structures without special geometries the amplification of the seed field is not quite as expected from these simple collapse models, with a rough power‐law dependence but a higher value of α (Dolag et al 1999, 2005; Roettiger et al 1999). King & Coles (2006) showed that an average over small‐scale collapses leads to an average value of α which is higher than the isotropic value α= 2/3; the average of a non‐linear function is not the same as the non‐linear function of the average. Moreover, other phenomena, such as mergers and anisotropies, act to enhance the field still further.…”

Section: Numerical Calculationsmentioning

confidence: 99%

The growth of baryonic structure in the presence of cosmological magnetic pressure

Gazzola¹,

King²,

Pearce³

et al. 2007

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We follow the growth of baryonic structure in the presence of a magnetic field within an approximate cosmological magnetohydrodynamic simulation, produced by adding an (isotropic) magnetic pressure related to the local gas pressure. We perform an ensemble of these simulations to follow the amplification of the field with time. By using a variety of initial field strengths and changing the slope of the power law that governs the way the field grows with increasing density, we span the range of current observations and demonstrate the size of the effect realistic magnetic fields could have on the central density of groups and clusters. A strong magnetic field significantly reduces the central gas density which, in turn, reduces observable quantities such as the X‐ray luminosity.

show abstract

Amplification of primordial magnetic fields by anisotropic gravitational collapse

Cited by 11 publications

References 18 publications

Non-Thermal Processes in Cosmological Simulations

Non-Thermal Processes in Cosmological Simulations

Cosmological MHD simulation of a cooling flow cluster

The growth of baryonic structure in the presence of cosmological magnetic pressure

Contact Info

Product

Resources

About