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Shear dynamo problem: Quasilinear kinematic theory
S. Sridhar, Kandaswamy Subramanian
Large-scale dynamo action due to turbulence in the presence of a linear shear flow is studied. Our treatment is quasilinear and kinematic but is non perturbative in the shear stren…
Galactic dynamo action in presence of stochastic alpha and shear
Sharanya Sur, Kandaswamy Subramanian
Using a one-dimensional -dynamo model appropriate to galaxies, we study the possibility of dynamo action driven by a stochastic alpha effect and shear. To determine the field e…
Nonlinear magnetic diffusivity and alpha tensors in helical turbulence
A. Brandenburg, K. -H. Rädler, M. Rheinhardt +1
The effect of a dynamo-generated mean magnetic field of Beltrami type on the mean electromotive force is studied. In the absence of the mean magnetic field the turbulence is assume…
Primordial magnetic fields and formation of molecular hydrogen
Shiv K Sethi, Biman B. Nath, Kandaswamy Subramanian
We study the implications of primordial magnetic fields for the thermal and ionization history of the post-recombination era. In particular we compute the effects of dissipation of…
Magnetizing the universe
Kandaswamy Subramanian
The origin of cosmic magnetism is an issue of fundamental importance in astrophysics. We review here some of the ideas of how large scale magnetic fields in the universe, particula…
Constrained semi-analytical models of Galactic outflows
Saumyadip Samui, Kandaswamy Subramanian, Raghunathan Srianand
We present semi-analytic models of galactic outflows, constrained by available observations on high redshift star formation and reionization. Galactic outflows are modeled in a man…
Simulations of the anisotropic kinetic and magnetic alpha effects
A. Brandenburg, K. Subramanian
The validity of a closure called the minimal tau approximation (MTA), is tested in the context of dynamo theory, wherein triple correlations are assumed to provide relaxation of th…
Kinetic and magnetic alpha effects in nonlinear dynamo theory
Sharanya Sur, Kandaswamy Subramanian, Axel Brandenburg
The backreaction of the Lorentz force on the alpha-effect is studied in the limit of small magnetic and fluid Reynolds numbers, using the first order smoothing approximation (FOSA)…
Probing the star formation history using the redshift evolution of luminosity functions
Saumyadip Samui, Raghunathan Srianand, Kandaswamy Subramanian
We present a self-consistent, semi-analytical LCDM model of star formation and reionization. For the cosmological parameters favored by the WMAP data, our models consistently repro…
Primordial magnetic fields and CMB anisotropies
Kandaswamy Subramanian
Possible signatures of primordial magnetic fields on the Cosmic Microwave Background (CMB) temperature and polarization anisotropies are reviewed. The signals that could be searche…
Galactic dynamo and helicity losses through fountain flow
Anvar Shukurov, Dmitry Sokoloff, Kandaswamy Subramanian +1
Nonlinear behaviour of galactic dynamos is studied, allowing for magnetic helicity removal by the galactic fountain flow. A suitable advection speed is estimated, and a one-dimensi…
The origin and evolution of cluster magnetism
A. Shukurov, K. Subramanian, N. E. L. Haugen
Random motions can occur in the intergalactic gas of galaxy clusters at all stages of their evolution. Depending on the poorly known value of the Reynolds number, these motions can…
Magnetic helicity density and its flux in weakly inhomogeneous turbulence
Kandaswamy Subramanian, Axel Brandenburg
A gauge invariant and hence physically meaningful definition of magnetic helicity density for random fields is proposed, using the Gauss linking formula, as the density of correlat…
Can Cosmic Rays Heat the Intergalactic Medium?
Saumyadip Samui, Kandaswamy Subramanian, Raghunathan Srianand
Supernova explosions in the early star forming galaxies will accelerate cosmic rays (CRs). CRs are typically confined in the collapsed objects for a short period before escaping in…
Evolving turbulence and magnetic fields in galaxy clusters
Kandaswamy Subramanian, Anvar Shukurov, Nils Erland L. Haugen
We discuss, using simple analytical models and MHD simulations, the origin and parameters of turbulence and magnetic fields in galaxy clusters. Three physically distinct regimes ca…
Minimal tau approximation and simulations of the alpha effect
A. Brandenburg, K. Subramanian
The validity of a closure called the minimal tau approximation (MTA), is tested in the context of dynamo theory, wherein triple correlations are assumed to provide relaxation of th…
CMB Anisotropy Due to Tangled magnetic fields in re-ionized models
T. R. Seshadri, Kandaswamy Subramanian
Primordial tangled cosmological Magnetic Fields source rotational velocity perturbations of the baryon fluid, even in the post-recombination universe. These vortical modes inturn l…
The Physics of CMBR Anisotropies
Kandaswamy Subramanian
The observed structures in the universe are thought to have arisen from gravitational instability acting on small fluctuations generated in the early universe. These spatial fluctu…
Nonlinear current helicity fluxes in turbulent dynamos and alpha quenching
Kandaswamy Subramanian, Axel Brandenburg
Large scale dynamos produce small scale current helicity as a waste product that quenches the large scale dynamo process (alpha effect). This quenching can be catastrophic (i.e.int…
Primordial Magnetic Fields in the Post-recombination Era and Early Reionization
Shiv K. Sethi, Kandaswamy Subramanian
We explore the ways in which primordial magnetic fields influence the thermal and ionization history of the post-recombination universe. After recombination the universe becomes mo…
Astrophysical magnetic fields and nonlinear dynamo theory
Axel Brandenburg, Kandaswamy Subramanian
The current understanding of astrophysical magnetic fields is reviewed, focusing on their generation and maintenance by turbulence. In the astrophysical context this generation is…
Hyperdiffusion in non-linear, large and small-scale turbulent dynamos
Kandaswamy Subramanian
The generation of large-scale magnetic fields is generically accompanied by the more rapid growth of small-scale fields. The growing Lorentz force due to these fields back reacts o…
Small-scale microwave background anisotropies due to tangled primordial magnetic fields
Kandaswamy Subramanian, John D. Barrow
An inhomogeneous cosmological magnetic field creates vortical perturbations that survive Silk damping on much smaller scales than compressional modes. This ensures that there is no…
Magnetic helicity in galactic dynamos
Kandaswamy Subramanian
Magnetic fields correlated on kiloparsec scales are seen in spiral galaxies. Their origin could be due to amplification of a small seed field by a turbulent galactic dynamo. We rev…