Power spectra of solar wind magnetic field and velocity fluctuations more closely resemble those turbulent fluids (spectral index −5/3) than they do predictions for magnetofluid turbulence (a −3/2 index). Furthermore, the amount is heated by uncertain. To aid in study both these issues, we report numerically derived energy cascade rates magnetohydrodynamic (MHD) compare them with MHD phenomenologies. Either commonly predicted spectral indices 5/3 3/2 are consistent simulations. Explicit...

Solar wind frequency spectra show a distinct steepening of the ƒ −5/3 power law inertial range spectrum at frequencies above Doppler‐shifted ion cyclotron frequency. This is commonly attributed to dissipation due wave‐particle interactions. We consider extent which this can be described, using magnetohydrodynamic formulation that includes Hall term. An important characteristic MHD although resonance included, there no energy. In study we use compressible code with constant magnetic field and...

An exact analytical form of Sagdeev pseudopotential has been derived for a two electron temperature warm ion plasma, from which acoustic rarefactive solitary wave solutions could be investigated wide range different plasma parameters, viz., (σ), cold to hot ratio (β), and initial concentration (μ). Explicitly large Mach numbers have obtained increasing ratios, an condition the upper bound number such wave. It is found that width these waves obey Korteweg–de Vries soliton-type behavior only...

In the Helicon eXperimental (HeX) device, geometric aperture is fixed, but position of magnetic can be varied. Working with Argon gas in pressure range 1 − 10 × 4 mbar, an annular plasma (density ∼ 16 m 3) formed downstream, always front aperture. This occurs irrespective relative or presence a radial electric field. contrary to earlier proposition made by others that field necessary produce hollow profile. Instead, ionization neutrals radially outer region tail electrons, rotating fast due...

Abstract. The presence of dynamic, large amplitude solitary waves in the auroral regions space is well known. Since their velocities are order ion acoustic speed, they may be considered as being generated from nonlinear evolution waves. However, do not show expected width-amplitude correlation for K-dV solitons. Recent POLAR observations have actually revealed that low altitude rarefactive associated with an increase width increasing amplitude. This indicates a weakly theory appropriate to...

An investigation is conducted on how low-frequency, ω<Ωi, magnetohydrodynamic oscillations in a warm plasma may undergo transition from coherent state to one of turbulence. A driven/dissipative derivative nonlinear Schrödinger (DNLS) equation derived the fluid equations. The time evolution an arbitrary spectrum waves analyzed case where k-mode unstable, with rest damped. It found that order chaos system correlated existence or absence ‘‘breathing’’ solitons associated conservative system.

Spacecraft observations of magnetic field fluctuations in the solar wind reveals a “Maltese Cross” pattern two‐dimensional correlation function measurements [ Matthaeus et al. , 1990]. This suggests presence two components: with their (Fourier) wave vector approximately parallel to ambient (e.g., slab turbulence) and perpendicular quasi turbulence). To date, appearance such has never been reproduced from numerical simulation studies. Here we present results several MHD simulations that...

We examine numerically the influence of Hall effect corrections to Ohm's law upon decay homogeneous compressible magnetohydrodynamic turbulence and conclude that there are no significant differences in global rate associated with . This affirms expectations energy is controlled by large‐scale eddies.

We examine the influence of Hall effect and MHD turbulence on reconnection rate a large scale periodic sheet pinch in 2.5 dimensional compressible MHD. Simulations indicate that is enhanced both by increasing parameter amplitude.

The traditional view that solar wind fluctuations are well‐described as a spectrum of parallel‐propagating Alfvén waves has been challenged many times but is still frequently encountered perspective. Here we examine whether it remains consistent to most the fluctuation energy resident in situations which there also present either transverse pressure‐balanced (PB) magnetic structures or velocity shears. We address these questions through direct simulation compressible magnetohydrodynamics,...

It is observed that the presence of a minority component cooler electrons in three plasma plays deterministic role evolution solitary waves, double layers, or newly discovered structures called supersolitons. The inclusion single electron produces sharp increase nonlinearity spite decrease overall energy system. effect maximizes at certain critical value number density (typically 15%–20%) giving rise to hump amplitude variation profile. For larger amplitudes, leads forbidden region ambient...

The development of anisotropies in an initially isotropic spectrum is studied numerically for compressible magnetohydrodynamic (MHD) turbulence the presence Hall term. Building on a previous study where it was shown that spectral cascades MHD system differ from standard case, particularly at high cross-helicities, we use cross-helicity initial state to variety mean magnetic field strengths and sonic Mach numbers. Strong anisotropies, which maximize ion-inertial length scale, appear several...

Abstract. Recent high resolution measurements of POLAR and FAST satellites have revealed two-dimensional coherent structures in the polar cap boundary layer (PCBL) region. Since ion temperature is often observed to be greater than electron this region, acoustic waves can exist as a normal mode plasma system. It shown that nonlinear evolution such modelled by coupled Davey-Stewartson I equations. These equations, which are generalization Schrödinger equation two dimensions, admit...

The growth of parametric instabilities, which may lead to the development a turbulent cascade, is studied using magnetohydrodynamic (MHD) code that permits nonlinear couplings in parallel direction ambient magnetic field and one perpendicular direction. Compressibility included form polytropic equation state. Parametric instabilities associated with parallel‐propagating decay instability are found dominate low‐beta case. An obliquely propagating filamentationlike dominates high‐beta n th...

The existence domain of a fully nonlinear positive amplitude electron acoustic solitary wave has been studied in four‐component plasma composed warm magnetized electrons, beam, and energetic multi‐ion species with ions hotter than the electrons ( T i > e ). A Sagdeev pseudopotential technique used to obtain evolution equation for propagating obliquely ambient magnetic field. It is observed that ion temperatures concentrations play crucial role determining characteristics wave. With large...

The phase portrait analysis of super solitary waves has revealed a new kind intermediate solution which defines the boundary between two types waves, viz., Type I and II. A wave is known to be associated with an double layer while II no such association. at flat top structure called wave. Its characteristics resemble amalgamation layer. It was found that, mathematically, kinds structures may emerge due presence extra nonlinearity. Although they are relatively unfamiliar in realm plasma...

Low‐frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much that can be thought of as nearly perfect Alfvén waves. Evidence from Helios Ulysses spacecraft suggest strongly these emanate corona with high correlation flat power spectra (∼ f −1 ). These constitute a source free energy for turbulent cascade kinetic to wave numbers, evolves most rapidly vicinity shears heliospheric current sheet. Numerical solutions both compressible...

The compressible extensions of time asymptotic relaxation states incompressible two-dimensional magnetohydrodynamic turbulence are studied. A polytropic equation state is used with viscous and resistive dissipation. case known to allow three distinct types behavior: magnetic energy dominated relaxation, kinetic cross helicity relaxation. At low Mach numbers the scenario reproducible from simulations, compressibility plays only a secondary role. moderate, but still subsonic, processes...

Localized electron temperature and density peaking at different axial locations in the downstream helicon plasma have been observed a linear device with both geometrical magnetic expansion. The discharge is produced an right helical antenna powered by RF source operating 13.56 MHz. Axial wave field measurement shows presence of damped waves standing character folded into it even low densities ( m). measured wavelength just about twice length phase velocity almost speed required for impact...

Measured and calculated positron binding energies are presented for a range of hydrocarbons with up to six carbon atoms (viz., methane, acetylene, ethylene, ethane, propane, butane, hexane) their chlorinated counterparts. Both experiment theory confirm the large effect that chlorine have on energy strong sensitivity exact position atoms. The experimental been obtained by measuring resonant annihilation using trap-based beam. calculations performed previously developed...

Positrons attach to molecules in vibrationally resonant two-body collisions that result greatly enhanced annihilation rates. Measurements of as a function positron energy are presented for benzene using cryogenic, trap-based beam. They establish binding 132±3 meV test state-of-the-art theoretical calculations, and they exhibit many unexpected resonances, likely due combination overtone vibrational modes. The relationship these results the unique π-bonded structure is discussed.

Measurements are presented for the low-energy positron annihilation spectra of alkane molecules propane through octane. The downshift vibrational Feshbach resonances infrared-active C-H stretch modes is used to obtain updated values positron-molecule binding energies these molecules. These correct previously reported which had systematic energy shifts due several small, but significant, errors in analyses. Once corrected, old and new measured good agreement. This analysis procedure applied...

Anomalous width–amplitude variations were observed in large amplitude rarefactive solitary waves which show increasing width with amplitude, contrasting the usual reciprocal relation between square of and beyond a certain value plasma parameters [S. S. Ghosh, K. A. N. Sekar Iyengar, Phys. Plasmas, 3, 3939 (1996)]. For limiting maximum “increasing width” wave tends to double layer-like solution. The overall variation was found depend crucially on specific parameter space. From detailed...

Theory suggests that three distinct types of turbulence can occur in the low Mach number limit polytropic flow: nearly incompressible flows dominated by vorticity, pure acoustic compression, and characterized near statistical equipartition vorticity compressions. Distinctions between these kinds are investigated here direct numerical simulation two-dimensional compressible hydrodynamic turbulence. Dynamical scalings density fluctuations, examination ratio transverse to longitudinal velocity...

A numerical study of the evolution cross helicity in driven/dissipative magnetohydrodynamics (MHD) is presented. The magnetofluid incompressible and a two-dimensional (2-D) periodic geometry considered. Cross helicity, measure correlation between fluctuations magnetic field velocity field, injected by use correlated Gaussian forcing over finite bandwidth wavenumber. Numerical experiments include driving initially uncorrelated spectra with highly anticorrelated forcing. recurring persistent...