Jean Ramirez Perez | Universidad Tecnologica del Peru UTP (original) (raw)

Uploads

Papers by Jean Ramirez Perez

Research paper thumbnail of Theory and simulation of sheared flows and drift waves in the Large Plasma Device and the Helimak

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Codon populations in single-stranded whole human genome DNA Are fractal and fine-tuned by the Golden Ratio 1.618

Interdisciplinary sciences, computational life sciences, 2010

This new bioinformatics research bridges Genomics and Mathematics. We propose a universal "F... more This new bioinformatics research bridges Genomics and Mathematics. We propose a universal "Fractal Genome Code Law": The frequency of each of the 64 codons across the entire human genome is controlled by the codon's position in the Universal Genetic Code table. We analyze the frequency of distribution of the 64 codons (codon usage) within single-stranded DNA sequences. Concatenating 24 Human chromosomes, we show that the entire human genome employs the well known universal genetic code table as a macro structural model. The position of each codon within this table precisely dictates its population. So the Universal Genetic Code Table not only maps codons to amino acids, but serves as a global checksum matrix. Frequencies of the 64 codons in the whole human genome scale are a self-similar fractal expansion of the universal genetic code. The original genetic code kernel governs not only the micro scale but the macro scale as well. Particularly, the 6 folding steps of cod...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical modeling of anisotropic 3D Drift-Alfven turbulence

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectra and structure of MHD turbulence

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Imbalanced Magnetohydrodynamic Turbulence: Numerics and Theory

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Statistical Analysis of Current Sheets in Turbulent MHD Simulations

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Scaling Laws in Magnetohydrodynamics: Simulations vs Observations

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical simulations of anisotropic plasmas using a modified ZEUS-MP

Bookmarks Related papers MentionsView impact

Research paper thumbnail of On the Physics of Kinetic-Alfven Turbulence

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Scaling Properties of Small-Scale Fluctuations in Magnetohydrodynamic Turbulence

The Astrophysical Journal, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Computing Coherent Structures with Chebyshev-Fourier Pseudospectral Techniques in Confinement Systems

Chebyshev-tau pseudospectral methods have been widely used for decades in the linear and nonlinea... more Chebyshev-tau pseudospectral methods have been widely used for decades in the linear and nonlinear simulations of neutral fluid dynamics. In this work, we apply these techniques to different reduced models of fluid like plasma equations that describe various instabilities commonly present in many plasma confinement configurations, ranging from laboratory to space plasmas. Nonlinear high-resolution simulations are performed for a plasma slab, periodic in one direction and satisfying Dirichlet boundary conditions in the other. As opposed to Fourier-Fourier methods, usually applied to homogeneous problems, the Chebyshev-Fourier method allows for the study of equilibrium states that are inhomogeneous along one direction and have Dirichlet, Neumann or Robin boundary conditions. Adaptive fifth/sixth order RK time integration scheme is used to advance the initial condition. Simulations show the formation of long-lived coherent structures from different equilibrium states with a random nois...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Nonlinear MHD Simulations of Sheared Flows and Turbulence in the Helimak

We report results of three-dimensional nonlinear numerical simulations and theory for a magnetohy... more We report results of three-dimensional nonlinear numerical simulations and theory for a magnetohydrodynamic slab model of the Helimak, using magnetic and flow profiles based on experimental data. The Helimak experiment was designed to study the interaction between sheared mass flows and ambient turbulence in a confined plasma. The experiment is well modeled as a bounded magnetized jet in a slab geometry, with no slip boundary conditions in the cross-stream direction, and periodic boundary conditions in the other two directions. In the new nonlinear codewe have developed, space is discretized using a Chebyshev-collocation--Fourier-pseudospectral algorithm. Time is discretized with a third-order Runge-Kutta--Crank-Nicolson scheme. Important features of the code include three spatial dimensions, the presence of walls, and the inclusion of resistivity and viscosity. The nonlinear development of unstable eigenmodes, computed with a Chebyshev-tau algorithm, will be discussed. We analyze t...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical modeling of steady state MHD turbulence

An effective numerical setting for simulating universal regimes of steady state MHD turbulence is... more An effective numerical setting for simulating universal regimes of steady state MHD turbulence is presented. We show by means of high resolution numerical simulations that this setting allows one to investigate the most important features of weak and strong MHD turbulence, such as anisotropy, energy spectra, critical balance, dynamic alignment and the role of cross helicity. The relevance of the results to Solar Wind and Interstellar Medium (ISM) turbulence is discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of ERRATUM: “DIRECT NUMERICAL SIMULATIONS OF REFLECTION-DRIVEN, REDUCED MAGNETOHYDRODYNAMIC TURBULENCE FROM THE SUN TO THE ALFVÉN CRITICAL POINT” (2013, ApJ, 776, 124)

The Astrophysical Journal, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Perpendicular Ion Heating by Reduced Magnetohydrodynamic Turbulence

The Astrophysical Journal, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical studies of weak MHD turbulence

Results from numerical simulations of weak magnetohydrodynamic (MHD) turbulence in steady-state a... more Results from numerical simulations of weak magnetohydrodynamic (MHD) turbulence in steady-state are presented, with resolutions as high as 1024^2x256 grid points. Weak turbulence refers to the limit of MHD turbulence in which the energy transfer toward smaller scales results from the weak interaction between Alfv'en waves moving along of against a strong guide magnetic field. The energies of the Alfven waves moving in the opposite directions can be either equal, in which case the turbulence is called balanced, or unequal, in which case it is unbalanced. The numerical set up is optimized as to drive either balanced or unbalanced turbulent cascades. We obtain the spectra of Alfv'en waves for various degrees of imbalance and Reynolds numbers. We discuss our results and compare with recent theories of weak MHD turbulence.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Study of strong cross-field sheared flow with the vorticity probe in the Large Plasma Device

Physics of Plasmas, 2006

This work reports evidence for the existence of coherent structures in steady-state shear-flow dr... more This work reports evidence for the existence of coherent structures in steady-state shear-flow driven plasmas in the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] facility at UCLA. The measurements are performed with the vorticity probe (VP), a probe that directly measures the plasma vorticity associated with the E×B shear flow by means of a method that is both simpler and more accurate than the methods used in neutral fluids. Because the rate of change of vorticity is a key quantity in nonlinear models, as in the Hasegawa-Mima equation, its direct measurement is critical for verification purposes. The physical origin of the rate of change of plasma vorticity from E×B flow is the divergence of the ion polarization current. Vortex coherent structures occur when the vorticity is a nonlinear function of the stream function. Statistical properties of vorticity are reported and shown to be consistent with the types of coherent structures created by the Kelv...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Drift wave instability in the Helimak experiment

Physics of Plasmas, 2006

Electrostatic drift wave linear stability analysis is carried out for the Helimak configuration a... more Electrostatic drift wave linear stability analysis is carried out for the Helimak configuration and compared against experimental data. Density fluctuation and cross-spectrum measurements show evidence of a coherent mode propagating perpendicular to the magnetic field which becomes unstable at k⊥ρs∼0.15. By comparing the experimental results with the wave characteristic of linear two-fluid theory, this mode is identified as an unstable resistive drift wave driven by the density gradient and magnetic grad-B/curvature present in an otherwise magnetohydrodynamic stable steady-state equilibrium.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical simulations of strong incompressible magnetohydrodynamic turbulence

Physics of Plasmas, 2012

Magnetised plasma turbulence pervades the universe and is likely to play an important role in a v... more Magnetised plasma turbulence pervades the universe and is likely to play an important role in a variety of astrophysical settings. Magnetohydrodynamics (MHD) provides the simplest theoretical framework in which phenomenological models for the turbulent dynamics can be built. Numerical simulations of MHD turbulence are widely used to guide and test the theoretical predictions; however, simulating MHD turbulence and accurately measuring its scaling properties is far from straightforward. Computational power limits the calculations to moderate Reynolds numbers and often simplifying assumptions are made in order that a wider range of scales can be accessed. After describing the theoretical predictions and the numerical approaches that are often employed in studying strong incompressible MHD turbulence, we present the findings of a series of high-resolution direct numerical simulations. We discuss the effects that insufficiencies in the computational approach can have on the solution and...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum of Weak Magnetohydrodynamic Turbulence

Physical Review Letters, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Theory and simulation of sheared flows and drift waves in the Large Plasma Device and the Helimak

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Codon populations in single-stranded whole human genome DNA Are fractal and fine-tuned by the Golden Ratio 1.618

Interdisciplinary sciences, computational life sciences, 2010

This new bioinformatics research bridges Genomics and Mathematics. We propose a universal "F... more This new bioinformatics research bridges Genomics and Mathematics. We propose a universal "Fractal Genome Code Law": The frequency of each of the 64 codons across the entire human genome is controlled by the codon's position in the Universal Genetic Code table. We analyze the frequency of distribution of the 64 codons (codon usage) within single-stranded DNA sequences. Concatenating 24 Human chromosomes, we show that the entire human genome employs the well known universal genetic code table as a macro structural model. The position of each codon within this table precisely dictates its population. So the Universal Genetic Code Table not only maps codons to amino acids, but serves as a global checksum matrix. Frequencies of the 64 codons in the whole human genome scale are a self-similar fractal expansion of the universal genetic code. The original genetic code kernel governs not only the micro scale but the macro scale as well. Particularly, the 6 folding steps of cod...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical modeling of anisotropic 3D Drift-Alfven turbulence

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectra and structure of MHD turbulence

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Imbalanced Magnetohydrodynamic Turbulence: Numerics and Theory

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Statistical Analysis of Current Sheets in Turbulent MHD Simulations

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Scaling Laws in Magnetohydrodynamics: Simulations vs Observations

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical simulations of anisotropic plasmas using a modified ZEUS-MP

Bookmarks Related papers MentionsView impact

Research paper thumbnail of On the Physics of Kinetic-Alfven Turbulence

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Scaling Properties of Small-Scale Fluctuations in Magnetohydrodynamic Turbulence

The Astrophysical Journal, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Computing Coherent Structures with Chebyshev-Fourier Pseudospectral Techniques in Confinement Systems

Chebyshev-tau pseudospectral methods have been widely used for decades in the linear and nonlinea... more Chebyshev-tau pseudospectral methods have been widely used for decades in the linear and nonlinear simulations of neutral fluid dynamics. In this work, we apply these techniques to different reduced models of fluid like plasma equations that describe various instabilities commonly present in many plasma confinement configurations, ranging from laboratory to space plasmas. Nonlinear high-resolution simulations are performed for a plasma slab, periodic in one direction and satisfying Dirichlet boundary conditions in the other. As opposed to Fourier-Fourier methods, usually applied to homogeneous problems, the Chebyshev-Fourier method allows for the study of equilibrium states that are inhomogeneous along one direction and have Dirichlet, Neumann or Robin boundary conditions. Adaptive fifth/sixth order RK time integration scheme is used to advance the initial condition. Simulations show the formation of long-lived coherent structures from different equilibrium states with a random nois...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Nonlinear MHD Simulations of Sheared Flows and Turbulence in the Helimak

We report results of three-dimensional nonlinear numerical simulations and theory for a magnetohy... more We report results of three-dimensional nonlinear numerical simulations and theory for a magnetohydrodynamic slab model of the Helimak, using magnetic and flow profiles based on experimental data. The Helimak experiment was designed to study the interaction between sheared mass flows and ambient turbulence in a confined plasma. The experiment is well modeled as a bounded magnetized jet in a slab geometry, with no slip boundary conditions in the cross-stream direction, and periodic boundary conditions in the other two directions. In the new nonlinear codewe have developed, space is discretized using a Chebyshev-collocation--Fourier-pseudospectral algorithm. Time is discretized with a third-order Runge-Kutta--Crank-Nicolson scheme. Important features of the code include three spatial dimensions, the presence of walls, and the inclusion of resistivity and viscosity. The nonlinear development of unstable eigenmodes, computed with a Chebyshev-tau algorithm, will be discussed. We analyze t...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical modeling of steady state MHD turbulence

An effective numerical setting for simulating universal regimes of steady state MHD turbulence is... more An effective numerical setting for simulating universal regimes of steady state MHD turbulence is presented. We show by means of high resolution numerical simulations that this setting allows one to investigate the most important features of weak and strong MHD turbulence, such as anisotropy, energy spectra, critical balance, dynamic alignment and the role of cross helicity. The relevance of the results to Solar Wind and Interstellar Medium (ISM) turbulence is discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of ERRATUM: “DIRECT NUMERICAL SIMULATIONS OF REFLECTION-DRIVEN, REDUCED MAGNETOHYDRODYNAMIC TURBULENCE FROM THE SUN TO THE ALFVÉN CRITICAL POINT” (2013, ApJ, 776, 124)

The Astrophysical Journal, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Perpendicular Ion Heating by Reduced Magnetohydrodynamic Turbulence

The Astrophysical Journal, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical studies of weak MHD turbulence

Results from numerical simulations of weak magnetohydrodynamic (MHD) turbulence in steady-state a... more Results from numerical simulations of weak magnetohydrodynamic (MHD) turbulence in steady-state are presented, with resolutions as high as 1024^2x256 grid points. Weak turbulence refers to the limit of MHD turbulence in which the energy transfer toward smaller scales results from the weak interaction between Alfv'en waves moving along of against a strong guide magnetic field. The energies of the Alfven waves moving in the opposite directions can be either equal, in which case the turbulence is called balanced, or unequal, in which case it is unbalanced. The numerical set up is optimized as to drive either balanced or unbalanced turbulent cascades. We obtain the spectra of Alfv'en waves for various degrees of imbalance and Reynolds numbers. We discuss our results and compare with recent theories of weak MHD turbulence.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Study of strong cross-field sheared flow with the vorticity probe in the Large Plasma Device

Physics of Plasmas, 2006

This work reports evidence for the existence of coherent structures in steady-state shear-flow dr... more This work reports evidence for the existence of coherent structures in steady-state shear-flow driven plasmas in the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] facility at UCLA. The measurements are performed with the vorticity probe (VP), a probe that directly measures the plasma vorticity associated with the E×B shear flow by means of a method that is both simpler and more accurate than the methods used in neutral fluids. Because the rate of change of vorticity is a key quantity in nonlinear models, as in the Hasegawa-Mima equation, its direct measurement is critical for verification purposes. The physical origin of the rate of change of plasma vorticity from E×B flow is the divergence of the ion polarization current. Vortex coherent structures occur when the vorticity is a nonlinear function of the stream function. Statistical properties of vorticity are reported and shown to be consistent with the types of coherent structures created by the Kelv...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Drift wave instability in the Helimak experiment

Physics of Plasmas, 2006

Electrostatic drift wave linear stability analysis is carried out for the Helimak configuration a... more Electrostatic drift wave linear stability analysis is carried out for the Helimak configuration and compared against experimental data. Density fluctuation and cross-spectrum measurements show evidence of a coherent mode propagating perpendicular to the magnetic field which becomes unstable at k⊥ρs∼0.15. By comparing the experimental results with the wave characteristic of linear two-fluid theory, this mode is identified as an unstable resistive drift wave driven by the density gradient and magnetic grad-B/curvature present in an otherwise magnetohydrodynamic stable steady-state equilibrium.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical simulations of strong incompressible magnetohydrodynamic turbulence

Physics of Plasmas, 2012

Magnetised plasma turbulence pervades the universe and is likely to play an important role in a v... more Magnetised plasma turbulence pervades the universe and is likely to play an important role in a variety of astrophysical settings. Magnetohydrodynamics (MHD) provides the simplest theoretical framework in which phenomenological models for the turbulent dynamics can be built. Numerical simulations of MHD turbulence are widely used to guide and test the theoretical predictions; however, simulating MHD turbulence and accurately measuring its scaling properties is far from straightforward. Computational power limits the calculations to moderate Reynolds numbers and often simplifying assumptions are made in order that a wider range of scales can be accessed. After describing the theoretical predictions and the numerical approaches that are often employed in studying strong incompressible MHD turbulence, we present the findings of a series of high-resolution direct numerical simulations. We discuss the effects that insufficiencies in the computational approach can have on the solution and...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum of Weak Magnetohydrodynamic Turbulence

Physical Review Letters, 2009

Bookmarks Related papers MentionsView impact