This work presents the model equations governing the excitation of weak whistler by a stronger Kinetic Alfvén wave (KAW) in the plasma having β value (β ≫ me/mi, where beta is the ratio of the ion sound speed to the Alfvén speed), applicable to magnetotail in Earth's magnetosphere, when the ponderomotive nonlinearity is incorporated in the KAW dynamics. Numerical solution of the model equations has been obtained when the incident pump KAW is having a small perturbation. Energy exchange between main KAW and perturbation and the resulting localized structures of the KAW have been studied. A weak whistler signal propagating in these localized structures is amplified and leads to the development of envelope solitons. Our result reveals that the amplified (excited) whistler has an electric field power spectrum that is steeper than k−8/3. This result is consistent with recent observations by the Cluster spacecraft Eastwood et al. (Phys. Rev. Lett., vol. 102, 2009, 035001) in the magnetotail region of the Earth's magnetosphere.

This paper presents the nonlinear dynamics of the dispersive Alfvén wave (DAW) in the low-β plasmas (β≪me/mi; known as inertial Alfvén waves) applicable to solar corona. The pump DAW is perturbed by a low-frequency slow Alfvén wave (SW). When the ponderomotive nonlinearities are incorporated in the DAW and SW dynamics, the model equations of DAW and SW turn out to be the modified Zakharov system of equations (MZSE) Growth rate and threshold field for modulational (filamentation) instability have been calculated. The dependence of the growth rate on the perturbation wave number and the pump wave parameters such as k0xλe (inertial) has also been presented. It is obvious from this investigation that DAW can become unstable when it nonlinearly interacts with the SW and modulational instabilities can be triggered. The relevance of these investigations for solar corona has been discussed.

The effects of limiter biasing on the equilibrium density and potential profiles of the scrape-off layer (SOL) in tokamak plasma are investigated by including ionization and cross-field mobility. It is shown that a broadening of SOL can take place by the inclusion of ionization for low negative biasing. Various microinstabilities relevant for SOL plasmas have been studied. Generalized low-frequency dispersion relation is derived. It is shown that limiter biasing significantly modifies the SOL fluctuations. It is also shown that growth rate of conductive wall instability is smaller for negative biasing than positive biasing case. New mode, the modified Simon–Hoh, and ion temperature gradient instabilities are found to contribute significantly to the growth of curvature- and electron temperature-gradient-driven conductive wall instabilities.

We study the existence of stable axially and spherically symmetric plasma structures on the basis of the new nonlinear Schrödinger equation (NLSE) accounting for non-local electron nonlinearities. The numerical solutions of NLSE having the form of spatial solitions are obtained and their stability is analyzed. We discuss the possible application of the obtained results to the theoretical description of natural plasmoids in the atmosphere.

A theory of two-stream free-electron laser in a combined electromagnetic wiggler and an ion-channel guiding is developed. In the analysis, the electron trajectories and the small signal gain are derived by considering the effects of self-fields. Numerical calculations show that there are seven group's trajectories rather than nine groups reported in Mehdian and Saviz (2010 Chin. Phys. B 19(1), 014214). The comparison of the normalized gains and their corresponding normalized frequencies by employing the axial magnetic field and ion-channel guiding, with and without self-fields, in FEL has been studied numerically. The results show that the normalized maximum gain in FEL with axial magnetic is larger than that for using ion-channel guiding except in small region, but the results for their corresponding normalized frequencies are opposite.

A paraxial-like approach has been invoked to understand the nature of propagation of a hollow Gaussian beam (HGB) propagating in plasma under the influence of relativistic non-linearity. In this approach, the parameters are expanded in terms of the radial distance from the maximum of irradiance rather than that from the axis. This paper investigates the excitation of plasma wave in a hot collision less plasma by HGB. On account of the × force, a plasma wave at 2ω0 (here, ω0 is the pump laser frequency) is generated. The solution of the HGB has been obtained within the paraxial ray approximation. Filamentary structures of the laser beam are observed due to relativistic non-linearity.

The backward symplectic DIII-D map and continuous symplectic analog of the map for magnetic field line trajectories in the DIII-D [10] (Luxon, J. L. and Davis, L. E. 1985 Fusion Technol.8, 441) in natural canonical coordinates are used to calculate the magnetic footprint on the outboard collector plate of the DIII-D tokamak from the field errors and internal topological noise. The equilibrium generating function for the DIII-D used in the map very accurately represents the magnetic geometry of the DIII-D. The step-size of the map is kept considerably small so that the magnetic perturbation added from symplectic discretization of the Hamiltonian equations of the magnetic field line trajectories is very small. The natural canonical coordinates allow inverting to the real physical space. The combination of highly accurate equilibrium generating function, natural canonical coordinates, symplecticity, and small step-size then together gives a very accurate calculation of magnetic footprint. Radial variation of magnetic perturbation and the response of plasma to perturbation are not included. The footprint is in the form of toroidally winding helical strips. The area of footprint scales as 1st power of amplitude. The physical parameters as toroidal angle, length, and poloidal angle covered before striking, and the safety factor all have fractal structure. The average field diffusion near X-point for lines that strike and that do not strike differs by about four orders of magnitude. The flux loss decreases for high values of amplitude of perturbation.

We present numerical solution of a fully nonlinear electron kinetic equation in self-similar variables, which on the one hand has all features of a ‘standard’ hydrodynamics (ratios of the electron mean free path to the scale length γ ≡ λC/L 1), and on the other hand has no restriction on the smallness of the parameter γ. The self-similar variable approach reduces dimensionality of the space-dependent kinetic equation, thereby providing numerical analysis of the electron heat transport in the velocity space. The electron distribution structure and its super thermal power-law tail are examined.

PACS number(s): 52.25.Dg, 52.65.Ff, 52.50.-b

It is shown that in the earth's conductive ionospheric E-region, large-scale ultra low-frequency Rossby and Khantadze electromagnetic waves can propagate. Along with the prevalent effect of Hall conductivity for these waves, the latitudinal inhomogeneity of both the earth's angular velocity and the geomagnetic field becomes essential. Action of these effects leads to the coupled propagation of electromagnetic Rossby and Khantadze modes. Linear propagation properties of these waves are given in detail. It is shown that the waves lose the dispersing property for large values of wave numbers. Corresponding nonlinear solitary vortical structures are constructed. Conditions for such self-organization are given. It is shown that nonlinear large-scale vortices generate the stronger pulses of the geomagnetic field than the corresponding linear waves. Previous investigations are revised.

The model by Braginskii [1] (Braginskii, S. I. 1965 Transport processes in plasma. In: Review of Plasma Physics, Vol. 1 (ed. M.A. Leontovich). New York, NY: Consultants Bureau, pp. 205–311) for the viscous stress tensor is used to determine the shear and gyroviscous forces acting within a toroidally confined plasma. Comparison is made to a previous evaluation, which contains an inconsistent treatment of the radial derivative and neglects the effect of the pitch angle. Parallel viscosity contributes a radial shear viscous force, which may develop for sufficient vertical asymmetry to the ion velocity profile. An evaluation is performed of this radial viscous force for a tokamak near equilibrium, which indicates qualitative agreement between theory and measurement for impure plasma discharges with strong toroidal flow.

Magnetic reconnection in three dimensions (3D) is a natural extension from X-point reconnection in two dimensions. Of central importance in the 3D process is a localized non-ideal region within which the plasma and magnetic field decouple allowing for field line connectivity change. In practice, localized current structures provide this localization; however, mathematically a similar effect can be achieved with the localization of plasma resistivity instead. Physically though, such approaches are unrealistic, as anomalous resistivity requires very localized currents. Therefore, we wish to know how much information is lost in localizing η instead of current? In this work we develop kinematic models for torsional spine and fan reconnection using both localized η and localized current and compare the non-ideal flows predicted by each. We find that the flow characteristics are dictated almost exclusively by the form taken for the current profile with η acting only to scale the flow. We do, however, note that the reconnection mechanism is the same in each case. Therefore, from an understanding point of view, localized η models are still important first steps into exploring the role of non-ideal effects.