scholarly journals Primordial magnetic fields during the cosmic dawn in light of EDGES 21-cm signal

2020 ◽  
Vol 498 (1) ◽  
pp. 918-925 ◽  
Author(s):  
Ankita Bera ◽  
Kanan K Datta ◽  
Saumyadip Samui
Keyword(s):  
Magnetic Field ◽  
Cross Section ◽  
Magnetic Energy ◽  
Interaction Cross Section ◽  
Baryon Interaction ◽  
Dark Ages ◽  
The Standard Model ◽  
Standard Scenario ◽  
Primordial Magnetic Fields ◽  
The Magnetic Field

ABSTRACT We study prospects of constraining the primordial magnetic field (PMF) and its evolution during the dark ages and cosmic dawn in light of EDGES 21-cm signal. Our analysis has been carried out on a ‘colder IGM’ background which is one of the promising avenues to interpret the EDGES signal. We consider the dark matter-baryon interactions for the excess cooling. We find that the colder IGM suppresses both the residual free electron fraction and the coupling coefficient between the ionized and neutral components. The Compton heating also gets affected in colder IGM background. Consequently, the IGM heating rate due to the PMF enhances compared to the standard scenario. Thus, a significant fraction of the magnetic energy, for $B_0 \lesssim 0.5 \, {\rm nG}$, gets transferred to the IGM and the magnetic field decays at much faster rate compared to the simple (1 + z)2 scaling during the dark ages and cosmic dawn. This low PMF is an unlikely candidate for explaining the rise of the EDGES absorption signal at lower redshift. We also see that the PMF and DM-baryon interaction together introduces a plateau like feature in the redshift evolution of the IGM temperature. We find that the upper limit on the PMF depends on the underlying DM-baryon interaction. Higher PMF can be allowed when the interaction cross-section is higher and/or the DM particle mass is lower. Our study shows that the PMF with B0 up to ${\sim}0.4 \, {\rm nG}$, which is ruled out in the standard model, can be allowed if DM-baryon interaction with suitable cross-section and DM mass are considered.

scholarly journals PRIMORDIAL MAGNETIC FIELDS

1998 ◽  
Vol 07 (03) ◽  
pp. 331-349 ◽  
Author(s):  
KARI ENQVIST
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Particle Physics ◽  
Large Scale ◽  
Magnetic Energy ◽  
Galactic Magnetic Fields ◽  
Microscopic Field ◽  
Primordial Magnetic Fields ◽  
Primordial Magnetic Field ◽  
The Magnetic Field

The explanation of the observed galactic magnetic fields may require the existence of a primordial magnetic field. Such a field may arise during the early cosmological phase transitions, or because of other particle physics related phenomena in the very early universe reviewed here. The turbulent evolution of the initial, randomly fluctuating microscopic field to a large-scale macroscopic field can be described in terms of a shell model, which provides an approximation to the complete magnetohydrodynamics. The results indicate that there is an inverse cascade of magnetic energy whereby the coherence of the magnetic field is increased by many orders of magnitude. Cosmological seed fields roughly of the order of 10-20 G at the scale of protogalaxy, as required by the dynamo explanation of galactic magnetic fields, thus seem plausible.

CHOICE OF CONDITIONS FOR MHD SIMULATIONS ABOVE THE ACTIVE REGION, ALLOWING THE STUDY OF THE SOLAR FLARE MECHANISM

2021 ◽  
Vol 44 ◽  
pp. 92-95
Author(s):  
A.I. Podgorny ◽  
◽  
I.M. Podgorny ◽  
A.V. Borisenko ◽  
N.S. Meshalkina ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Flare ◽  
Magnetic Energy ◽  
Solar Radius ◽  
Computational Domain ◽  
Mhd Simulations ◽  
Flare Energy ◽  
Numerical Instabilities ◽  
The Magnetic Field

Primordial release of solar flare energy high in corona (at altitudes 1/40 - 1/20 of the solar radius) is explained by release of the magnetic energy of the current sheet. The observed manifestations of the flare are explained by the electrodynamical model of a solar flare proposed by I. M. Podgorny. To study the flare mechanism is necessary to perform MHD simulations above a real active region (AR). MHD simulation in the solar corona in the real scale of time can only be carried out thanks to parallel calculations using CUDA technology. Methods have been developed for stabilizing numerical instabilities that arise near the boundary of the computational domain. Methods are applicable for low viscosities in the main part of the domain, for which the flare energy is effectively accumulated near the singularities of the magnetic field. Singular lines of the magnetic field, near which the field can have a rather complex configuration, coincide or are located near the observed positions of the flare.

scholarly journals The development of magnetic field line wander by plasma turbulence

2017 ◽  
Vol 83 (4) ◽  
Author(s):  
Gregory G. Howes ◽  
Sofiane Bourouaine
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Magnetic Field Line ◽  
Large Scale ◽  
Magnetic Energy ◽  
Plasma Turbulence ◽  
Alfven Wave ◽  
Astrophysical Plasmas ◽  
Field Lines ◽  
The Magnetic Field

Plasma turbulence occurs ubiquitously in space and astrophysical plasmas, mediating the nonlinear transfer of energy from large-scale electromagnetic fields and plasma flows to small scales at which the energy may be ultimately converted to plasma heat. But plasma turbulence also generically leads to a tangling of the magnetic field that threads through the plasma. The resulting wander of the magnetic field lines may significantly impact a number of important physical processes, including the propagation of cosmic rays and energetic particles, confinement in magnetic fusion devices and the fundamental processes of turbulence, magnetic reconnection and particle acceleration. The various potential impacts of magnetic field line wander are reviewed in detail, and a number of important theoretical considerations are identified that may influence the development and saturation of magnetic field line wander in astrophysical plasma turbulence. The results of nonlinear gyrokinetic simulations of kinetic Alfvén wave turbulence of sub-ion length scales are evaluated to understand the development and saturation of the turbulent magnetic energy spectrum and of the magnetic field line wander. It is found that turbulent space and astrophysical plasmas are generally expected to contain a stochastic magnetic field due to the tangling of the field by strong plasma turbulence. Future work will explore how the saturated magnetic field line wander varies as a function of the amplitude of the plasma turbulence and the ratio of the thermal to magnetic pressure, known as the plasma beta.

scholarly journals THREE-BODY PHOTODISINTEGRATION OF 4He NUCLEUS BY LINEARLY POLARIZED PHOTONS

2019 ◽  
pp. 11-15
Author(s):  
A.A. Peretiatko ◽  
R.T. Murtazin ◽  
A.F. Khodyachikh
Keyword(s):  
Magnetic Field ◽  
Cross Section ◽  
Production Cross ◽  
Reaction Products ◽  
Azimuthal Distribution ◽  
Proton Production ◽  
Linearly Polarized ◽  
Three Body ◽  
Polarized Photons ◽  
The Magnetic Field

Experimental data are reported from studies of the reaction 4He(γ, pn)d through the use of the streamer chamber placed in the magnetic field and exposed to a linearly polarized photon beam from the electron linac LUE-2000. A structure has been revealed in the momentum distribution of deuterons. Studies were made into the effects of nucleon-deuteron correlation. The azimuthal distribution of reaction products and the asymmetry of proton production cross-section were measured. The obtained data were analyzed in the framework of the quasideuteron model.

Kinematic dynamo problem in a linear velocity field

1984 ◽  
Vol 144 ◽  
pp. 1-11 ◽  
Author(s):  
Ya. B. Zel'Dovich ◽  
A. A. Ruzmaikin ◽  
S. A. Molchanov ◽  
D. D. Sokoloff
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Velocity Field ◽  
Random Matrix ◽  
Magnetic Energy ◽  
Linear Velocity ◽  
Finite Conductivity ◽  
Kinematic Dynamo ◽  
Linear Velocity Field ◽  
The Magnetic Field

A magnetic field is shown to be asymptotically (t → ∞) decaying in a flow of finite conductivity with v = Cr, where C = Cζ(t) is a random matrix. The decay is exponential, and its rate does not depend on the conductivity. However, the magnetic energy increases exponentially owing to growth of the domain occupied by the field. The spatial distribution of the magnetic field is a set of thin ropes and (or) layers.

Fast magnetic field penetration into low resistivity plasma

2017 ◽  
Vol 83 (1) ◽  
Author(s):  
Amnon Fruchtman
Keyword(s):  
Magnetic Field ◽  
Energy Dissipation ◽  
Electric Field ◽  
Density Gradient ◽  
Magnetic Energy ◽  
Measured Velocity ◽  
Magnetic Field Penetration ◽  
The Magnetic Field ◽  
Uniform Plasma ◽  
Field Penetration

Penetration of a magnetic field into plasma that is faster than resistive diffusion can be induced by the Hall electric field in a non-uniform plasma. This mechanism explained successfully the measured velocity of the magnetic field penetration into pulsed plasmas. Major related issues have not yet been resolved. Such is the theoretically predicted, but so far not verified experimentally, high magnetic energy dissipation, as well as the correlation between the directions of the density gradient and of the field penetration.

Existence and Energy Balance of the Solar Dynamo

1993 ◽  
Vol 157 ◽  
pp. 19-23
Author(s):  
J.H.G.M. van Geffen
Keyword(s):  
Magnetic Field ◽  
Energy Balance ◽  
Energy Method ◽  
Magnetic Energy ◽  
Mean Field ◽  
Solar Dynamo ◽  
Ensemble Averaging ◽  
Dynamo Theory ◽  
The Magnetic Field ◽  
Mean Field Dynamo

The idea behind the use of ensemble averaging and the finite magnetic energy method of van Geffen and Hoyng (1992) is briefly discussed. Applying this method to the solar dynamo shows that the turbulence — an essential ingredient of traditional mean field dynamo theory — poses grave problems: the turbulence makes the magnetic field so unstable that it becomes impossible to recognize any period.

scholarly journals Multi-point observations of intermittency in the cusp regions

2007 ◽  
Vol 14 (4) ◽  
pp. 525-534 ◽  
Author(s):  
M. M. Echim ◽  
H. Lamy ◽  
T. Chang
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Haar Wavelet ◽  
Distribution Functions ◽  
Statistical Properties ◽  
Coarse Grained ◽  
Haar Wavelet Transform ◽  
Intermittent Behavior ◽  
Field Fluctuations ◽  
The Magnetic Field

Abstract. In this paper we investigate the statistical properties of magnetic field fluctuations measured by the four Cluster spacecraft in the cusp and close to the interface with the magnetospheric lobes, magnetopause and magnetosheath. At lower altitudes along the outbound orbit of 26 February 2001, the magnetic field fluctuations recorded by all four spacecraft are random and their Probability Distribution Functions (PDFs) are Gaussian at all scales. The flatness parameter, F – related to the kurtosis of the time series, is equal to 3. At higher altitudes, in the cusp and its vicinity, closer to the interface with the magnetopause and magnetosheath, the PDFs from all Cluster satellites are non-Gaussian and show a clear intermittent behavior at scales smaller than τG≈ 61 s (or 170 km). The flatness parameter increases to values greater than 3 for scales smaller than τG. A Haar wavelet transform enables the identification of the "events" that produce sudden variations of the magnetic field and of the scales that have most of the power. The LIM parameter (i.e. normalized wavelet power) indicates that events for scales below 65 s are non-uniformly distributed throughout the cusp passage. PDFs, flatness and wavelet analysis show that at coarse-grained scales larger than τG the intermittency is absent in the cusp. Fluctuations of the magnetic energy observed during the same orbit in the magnetosheath show PDFs that tend toward a Gaussian at scales smaller than τG found in the cusp. The flatness analysis confirms the decreasing of τG from cusp to magnetosheath. Our analysis reveals the turbulent cusp as a transition region from a non-intermittent turbulent state inside the magnetosphere to an intermittent turbulent state in the magnetosheath that has statistical properties resembling the solar wind turbulence. The observed turbulent fluctuations in the cusp suggests a phenomenon of nonlinear interactions of plasma coherent structures as in contemporary models of space plasma turbulence.

Toward a Contactless Hydrokinetic Energy Harvester: A Computational Magnetic Field Estimation

2018 ◽  
Author(s):  
Georgios Tsakyridis ◽  
Nikolaos I. Xiros ◽  
Michael M. Bernitsas
Keyword(s):  
Magnetic Field ◽  
Energy Harvesting ◽  
Attitude Control ◽  
Magnetic Levitation ◽  
Magnetic Energy ◽  
Hydrodynamic Drag ◽  
Core Element ◽  
Hydrokinetic Energy ◽  
Ferromagnetic Core ◽  
The Magnetic Field

Magnetic levitation (maglev) concepts are applied to a variety of industries such as the automotive, aerospace, or energy in order to accomplish different tasks: suspension and propulsion in maglev trains, rocket propulsion and spacecraft attitude control, centrifuge of nuclear reactors. In this paper, maglev is implemented in environmentally friendly hydrokinetic energy harvesting to achieve contactless bearing, thus, minimizing friction and improving efficiency. Generally, maglev systems exhibit higher efficiency and reduced maintenance while providing longer lifetime and higher durability when appropriate engineering design and control are applied. A Flow Induced Oscillation (FIO) energy-harvesting converter is considered in this work. To minimize friction in the support of the cylinder in FIO (vortex induced vibrations and galloping) due to high hydrodynamic drag, a maglev system is proposed. In the proposed configuration, a ferromagnetic core (element 1), of known dimensions, is considered under the effects of an externally imposed magnetic field. A second ferromagnetic element, of smaller dimensions, is then placed adjacent to the previous considered core. This particular configuration results in a non-homogenous magnetic field for element 1, caused by dimensional disparity. Specifically, the magnetic flux does not follow a linear path from the ferromagnetic core to element 2. A general electromagnetic analysis is conducted to derive an analytical form for the magnetic field of element 1. Subsequent numerical simulation validates the obtained formula. This distinct expression for the magnetic field is valuable towards calculating the magnetic energy of this specific configuration, which is essential to the design of the FIO energy harvesting converter considered in this work.

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