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The Hosking integral, which characterizes magnetic helicity fluctuations in subvolumes, is known to govern the decay of magnetically dominated turbulence. Here we show that, when the evolution of the magnetic field is controlled by the…

Plasma Physics · Physics 2023-09-14 Axel Brandenburg

Powerful lasers may in future produce magnetic fields that would allow us to study turbulent magnetohydrodynamic inverse cascade behavior. This has so far only been seen in numerical simulations. In the laboratory, however, the produced…

Plasma Physics · Physics 2025-08-04 Axel Brandenburg , Longqing Yi , Xianshu Wu

We show that in decaying hydromagnetic turbulence with initial kinetic helicity, a weak magnetic field eventually becomes fully helical. The sign of magnetic helicity is opposite to that of the kinetic helicity - regardless of whether or…

We present a new theoretical picture of magnetically dominated, decaying turbulence in the absence of a mean magnetic field. We demonstrate that such turbulence is governed by the reconnection of magnetic structures, and not by ideal…

Fluid Dynamics · Physics 2021-10-13 David N. Hosking , Alexander A. Schekochihin

Magnetic fields generated in the early Universe undergo turbulent decay during the radiation-dominated era. The decay is governed by a decay exponent and a decay time. It has been argued that the latter is prolonged by magnetic…

Cosmology and Nongalactic Astrophysics · Physics 2024-07-17 A. Brandenburg , A. Neronov , F. Vazza

In plasmas composed of massless electrically charged fermions, chirality can be interchanged with magnetic helicity while preserving the total chirality through the quantum chiral anomaly. The decay of turbulent energy in plasmas such as…

Plasma Physics · Physics 2023-05-15 Axel Brandenburg , Kohei Kamada , Jennifer Schober

The Saffman helicity invariant of Hosking and Schekochihin (2021, PRX 11, 041005), which we here call the Hosking integral, has emerged as an important quantity that may govern the decay properties of magnetically dominated nonhelical…

Plasma Physics · Physics 2022-11-11 Hongzhe Zhou , Ramkishor Sharma , Axel Brandenburg

It is well known that helical magnetohydrodynamic (MHD) turbulence exhibits an inverse transfer of magnetic energy from small to large scales, which is related to the approximate conservation of magnetic helicity. Recently, several…

Plasma Physics · Physics 2023-05-24 Andres Armua , Arjun Berera , Jaime Calderon Figueroa

Magnetic helicity plays a tremendously important role when it is different from zero on average. Most notably, it leads to the phenomenon of an inverse cascade. Here, we consider decaying magnetohydrodynamic (MHD) turbulence as well as some…

Plasma Physics · Physics 2023-05-29 Axel Brandenburg , Gustav Larsson

The extent to which large scale magnetic fields are susceptible to turbulent diffusion is important for interpreting the need for in situ large scale dynamos in astrophysics and for observationally inferring field strengths compared to…

Cosmology and Nongalactic Astrophysics · Physics 2015-11-18 Eric G. Blackman , Kandaswamy Subramanian

We present a new description of cosmological evolution of the primordial magnetic field under the condition that it is non-helical and its energy density is larger than the kinetic energy density. We argue that the evolution can be…

Cosmology and Nongalactic Astrophysics · Physics 2023-06-28 Fumio Uchida , Motoko Fujiwara , Kohei Kamada , Jun'ichi Yokoyama

We study the evolution of magnetic fields in freely decaying magnetohydrodynamic turbulence. By quasi-linearizing the Navier-Stokes equation, we solve analytically the induction equation in quasi-normal approximation. We find that, if the…

Astrophysics · Physics 2009-06-23 Leonardo Campanelli

We analyze the decay laws of the kinetic and magnetic energies and the evolution of correlation lengths in freely decaying incompressible magnetohydrodynamic (MHD) turbulence. Scale invariance of MHD equations assures that, in the case of…

Astrophysics · Physics 2009-11-10 Leonardo Campanelli

We show that decaying turbulent non-helical magnetic fields satisfy a self-similarity relation according to which the relevant scales increase as time passes (inverse cascade or inverse transfer). We compute analytically quantities which…

Cosmology and Nongalactic Astrophysics · Physics 2015-11-03 P. Olesen

In our conventional understanding, large-scale magnetic fields are thought to originate from an inverse cascade in the presence of magnetic helicity, differential rotation, or a magneto-rotational instability. However, as recent simulations…

Plasma Physics · Physics 2017-09-20 Kiwan Park

The evolution of magnetic fields is studied using simulations of forced helical turbulence with strong imposed shear. After some initial exponential growth, the magnetic field develops a large scale travelling wave pattern. The resulting…

Astrophysics · Physics 2009-10-31 Axel Brandenburg , Alberto Bigazzi , Kandaswamy Subramanian

The role of the different helical components of the magnetic and velocity fields in the inverse spectral transfer of magnetic helicity is investigated through Fourier shell-to-shell transfer analysis. Both magnetic helicity and energetic…

Plasma Physics · Physics 2021-07-07 Jean-Mathieu Teissier , Wolf-Christian Müller

The inverse transfer of magnetic helicity is investigated through direct numerical simulations of large-scale-mechanically-driven turbulent flows in the isothermal ideal magnetohydrodynamics (MHD) framework. The mechanical forcing is either…

Plasma Physics · Physics 2021-03-15 Jean-Mathieu Teissier , Wolf-Christian Müller

The ohmic decay of magnetic fields in the crusts of neutron stars is generally believed to be governed by Hall drift which leads to what is known as a Hall cascade. Here we show that helical and fractionally helical magnetic fields undergo…

High Energy Astrophysical Phenomena · Physics 2020-09-18 Axel Brandenburg

The free decay of non-helical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum $P_M(k,t)$ is self-similar in…

High Energy Astrophysical Phenomena · Physics 2015-06-22 Jonathan Zrake
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