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We have developed an analytic model to describe coupling of plasma and neutral fluids in the partially ionized heliosphere plasma medium. The sources employed in our analytic model are based on a $\kappa$-distribution as opposed to the Maxwellian distribution function. Our model uses the $\kappa$-distribution to analytically model the energetic neutral atoms that result in the heliosphere partially ionized plasma from charge exchange with the protons and subsequently produce a long tail which is otherwise not describable by the Maxwellian distribution. We present our analytic formulation and describe major differences in the sources emerging from these two distinct distributions., Comment: This paper has been accepted in Journal of Plasma Physics. It is in press

The NASA DS1 spacecraft encountered Comet P/Borrelly on September 22, 2001 at a distance of ∼2171 km on the sunward side of the comet. The flyby speed was ∼16.5 km s −1 . Using high temporal resolution (50 μs) absolute electric field amplitude measurements from a ∼1 m dipole antenna, new features of plasma clouds created by cometary dust impacts have been detected. The pulses have 1/ e exponential decays of ∼650 μs duration, exponentially shaped overshoots with rise times of ∼2 ms, and exponential-shaped overshoot decay times of ∼10 ms. Assuming a plasma temperature of 10 4 K, these pulse features have been explained as plasma cloud space charge effects from the electron, proton and heavy ion portions of the clouds passing the antenna. Complex pulse shapes were also detected. These are believed to be due to either plasma cloud scattering off of the spacecraft, or to secondary impacts. Small electric pulses of duration 10–15 ms of cometary origin were detected but are presently unexplained. The electric component of the plasma wave spectra at closest approach had an f −2.4 power law shape from 10 Hz to 1 kHz. The electron cyclotron frequency was approximately 1 kHz. One possible explanation of the wave spectrum is that whistler mode waves associated with phase steepened cometary plasma waves are dispersed, leading to the broad spectrum. Finally, based on the present results, a new type of low-cost, large-area dust detector is proposed.

For a non-relativistic electron–positron plasma the possibility of obtaining a relaxed state is explored. The Euler–Lagrange equations are obtained by minimizing the hyper-resistivity with generalized helicities and magnetofluid energy as the constraints. The relaxed state is shown to be morphologically similar to the steady-state equilibria of the electron–positron plasma system.

The field-reversed configuration (FRC) with a completely null toroidal field and finite plasma beta is shown to result from a relaxation mechanism based on the principle of minimum dissipation of energy.

Classical kinetic theory using Boltzmann statistics shows that the potential distribution φ(r) in the screening cloud surrounding a single test charge at rest within a plasma is governed by a three-dimensional spherically symmetric plasma screening equation ∇2φ(r)=A(exp(+αφ)−exp(−βφ)), r≠0, where A=4πn0e, α=e/Te, β=e/Ti, e=electronic charge, Te=electron temperature, Ti=ion temperature, and n0=electron and ion density at large distances from the charge Q. In this paper it is proved rigorously that any nontrivial solution of the screening equation must have the following property: If φ(r)=potential at a radial distance r and limr→∞ φ(r)=0, then, for any positive integer n, as r→0 either rnφ→+∞ and rnφ′→−∞ or rnφ→−∞ and rnφ′→+∞.

The dispersion characteristics of the circularly polarized electromagnetic waves propagating along a homogeneous magnetic field in a dusty plasma have been investigated theoretically. The Vlasov equation has been employed to find the response of the magnetized plasma particles where the dust grains form a static background of highly charged and massive centers having certain correlation. It is found that in addition to the usual Landau damping which is negligible in the low temperature approximation, a novel mechanism of damping of the Alfven waves due to the dust comes into play. The modification and damping of the Alfven waves depend on the dust perturbation parameters, unequal densities of plasma particles, the average correlation length of the dust grains, temperature of the plasma and the magnetic field.

We derive a generalized linear dispersion relation of waves in a strongly magnetized, compressible, homogeneous and isotropic quasineutral plasma. Starting from a two fluid model, describing distinguishable electron and ion fluids, we obtain a six order linear dispersion relation of magnetized waves that contains effects due to electron and ion inertia, finite plasma beta and angular dependence of phase speed. We investigate propagation characteristics of these magnetized waves in a regime where scale lengths are comparable with electron and ion inertial length scales. This regime corresponds essentially to the solar wind plasma where length scales, comparable with ion cyclotron frequency, lead to dispersive effects. These scales in conjunction with linear waves present a great deal of challenges in understanding the high frequency, small scale dynamics of turbulent fluctuations in the solar wind plasma., Comment: This paper is accepted in the Journal of Plasma Physics

We perform a fully self-consistent 3-D numerical simulation for a compressible, dissipative magneto-plasma driven by large-scale perturbations, that contain a fairly broader spectrum of characteristic modes, ranging from largest scales to intermediate scales and down to the smallest scales, where the energy of the system are dissipated by collisional (Ohmic) and viscous dissipations. Additionally, our simulation includes nonlinear interactions amongst a wide range of fluctuations that are initialized with random spectral amplitudes, leading to the cascade of spectral energy in the inertial range spectrum, and takes into account large scale as well as small scale perturbation that may have been induced by the background plasma fluctuations, also the non adiabatic exchange of energy leading to the migration of energy from the energy containing modes or randomly injected energy driven by perturbations and further dissipated by the smaller scales. Besides demonstrating the comparative decays of total energy and dissipation rate of energy, our results show the existence of a perpendicular component of current, thus clearly confirming that the self-organized state is non-force free., Paper is accepted in Journal of Plasma Physics - In Press

A nonlinear evolution equation governing the two dimensional propagation of fast and slow magnetosonic modes in a warm collisional plasma has been derived. This equation is a combination of Kadomtsev-Petviashvili (K-P) equation and the Burgers equation. The two dimensional K-P equation has two types of solitary wave solutions depending on the sign of the coefficients. One type is the usual planar type, the other is the lump solution. Both types of solitary wave solutions decay with time in the weak collisional limit. The two dimensional features of the amplitude and width of the lump or algebraic soliton have been discussed and the decay rates computed numerically. The decay rates depend on plasma beta and on the angle of propagation and the rates are different for the fast and the slow waves. At a certain angle of propagation the decay rates of both the modes are equal in the case of low beta plasma. Because of 2-D effects, the slow mode, although it has a lower collisional decay rate than the fast mode,...

It is known that ponderomotive forces produced by radial gradients in the RF energy can provide an effective stabilizing mechanism and create a stable window to the second stability regime. This problem is reexamined here with the introduction of axisymmetric toroidal rotation which itself is believed to have stabilizing influence on the ballooning modes on most flux surfaces except in the outer region. It is shown that the stabilizing effect is additive and an additional and important observation is that the outer region of the flux surfaces also gets stabilized by RF waves.

The usual theory of plasma relaxation, based on the selective decay of magnetic energy over the (global) magnetic helicity, predicts a force-free state for a plasma. Such a force-free state is inadequate to describe most realistic plasma systems occurring in laboratory and space plasmas as it produces a zero pressure gradient and cannot couple magnetic fields with flow. A different theory of relaxation has been proposed by many authors, based on a well-known principle of irreversible thermodynamics, the principle of minimum entropy production rate which is equivalent to the minimum dissipation rate (MDR) of energy. We demonstrate the applicability of minimum dissipative relaxed states to various self-organized systems of magnetically confined plasma in the laboratory and in the astrophysical context. Such relaxed states are shown to produce a number of basic characteristics of laboratory plasma confinement systems and solar arcade structure., Paper is accepted in JPP 2008

The heliopause (HP) separates the tenuous hot heliosheath plasma from the relatively dense cool magnetized plasma of the local interstellar medium (LISM). Fluid acceleration in the HP region can therefore drive Rayleigh-Taylor-like and Kelvin-Helmholtz- like instabilities. Charge exchange coupling of plasma ions and primary interstellar neutral atoms provides an effective gravity, suggesting the possibility of Rayleigh Taylor-like (RT-like) instabilities. Shear flow due to the velocity difference between the heliosheath and the interstellar flows drives Kelvin Helmholtz-like (KH-like) modes on the heliopause. Magnetic fields damp the classical KH instability. However, we show that energetic neutral atoms (ENAs) destabilize KH-modes,even in the presence of interplanetary and interstellar magnetic fields. We consider a model that includes a number of effects that are important in the heliosphere such as resonant change exchange between the primary neutrals and the solar wind plasma, ENAs from the inner heliosheath, plasma flows along the heliopause and magnetic fields in the inner and outer heliosheath. We find that the nose region is unstable to RT-like modes for HP parameters, while the shoulder region is unstable to a new instability that has the characteristics of a mixed RT-KH-like mode. These instabilities are not stabilized by typical values of the magnetic fields in the inner and outer heliosheath close to the nose and shoulder regions. Whereas ENAs have a stabilizing influence on the RT instability in the vicinity of the nose region (due to counter streaming), they have a destabilizing influence on the KH instability in the vicinity of the flanks. We find that even in the presence of interplanetary and interstellar magnetic fields, ENAs can drive a new form of KH-like instability on the flanks. An analysis of the collisional and anomalous magnetic field diffusion time scales shows that ideal MHD is an appropriate model at the HP. The interstellar magnetic field therefore drapes over the HP and does not diffuse into the inner heliosheath (IHS). However, RT-like, RT-KH-like, and KH-like instabilities serve to drag outer heliosheath (OHS)/interstellar magnetic field into the IHS, allowing for local reconnection of interplanetary and interstellar magnetic field. Such reconnection may 1) enhance the mixing of plasmas across the heliopause, and 2) provide open magnetic field lines that allow easy ingress of galactic cosmic rays into the heliosphere and easy loss of anomalous cosmic rays.

[1] It has been suggested that Magnetic Holes (MHs) are caused by perpendicular proton energization due to the Ponderomotive Force (PF) associated with phase steepened Alfven waves. Here we include particle finite Larmor radius (FLR) effects and the effects of ion gyroharmonics in the PF expression. The general expression for the PF is derived by using the hot plasma dielectric tensor from kinetic theory. The fully kinetic expression has a multiple resonance character which is not revealed in the fluid picture. It will be shown that by including such effects, the expression for the PF will be significantly altered, both at the low frequency and high frequency limit. Also, an explicit analytic expression for the PF keeping only the first order FLR terms is given for conceptual purposes for the readers.

The stability of the heliopause that separates the tenuous hot magnetized heliosheath plasma from the dense cool local interstellar magnetized plasma is examined using a fully general model that includes all the essential physical processes. Charge exchange coupling between plasma protons and primary interstellar neutral atoms provides an effective gravity that drives Rayleigh-Taylor (RT)-like instabilities. The velocity difference or shear between the heliosheath and interstellar flows, when coupled to energetic neutral atoms (ENAs), drives a Kelvin-Helmholtz (KH)-like instability on the heliopause. The shoulder region of the heliopause is unstable to a new instability that has characteristics of a mixed RT-KH-like mode. The instabilities are not stabilized by typical values of the magnetic fields in the inner and outer heliosheath (OHS). ENAs play an essential role in driving the KH-like instability, which is fully stabilized in their absence by magnetic fields. The nonlinear phase of these instabilities is briefly discussed. We also discuss the possibility that RT-like or mixed KH-RT-like instabilities drag outer heliosheath/very local interstellar medium (OHS/VLISM) magnetic field lines into the inner heliosheath (IHS) with the VLISM flow, and the possibility that IHS and VLISM magnetic field lines experience reconnection. Such reconnection may (1) greatly enhance the mixing ofmore » plasmas across the heliopause and (2) provide open magnetic field lines that allow easy ingress of galactic cosmic rays into the heliosphere and corresponding easy loss of anomalous cosmic rays from the heliosphere.« less

Relaxed States of a slightly resistive and turbulent magnetized plasma is obtained by invoking the principle of minimum dissipation which leads to curl curl curl B = \lambda B . A solution of the above equation is accomplished using the analytic continuation of the Chandrasekhar-Kendall eigenfunctions in the complex domain. The new features of this theory is to show (i) a single fluid can relax to an MHD equilibrium which can support pressure gradient even without a flow, (ii) field reversal (RFP) in states that are not force free., Comment: LateX, 10 pages, 5 figures (ps), 18 references

The spatial topology of magnetic field lines can be chaotic for fields generated by simple current configurations. This is illustrated for a system consisting of a circular current loop and a straight current wire. An asymmetric configuration of the current system leads to three-dimensional spatially chaotic magnetic fields. The motion of charged particles in these fields is not necessarily chaotic and exhibits intriguing dynamical properties. Particles having initial velocities closely aligned with the direction of the local magnetic field are likely to follow chaotic orbits in phase space. Other particles follow coherent and periodic orbits; these orbits being the same as in the symmetric current configuration for which the field lines are not chaotic. An important feature of particles with chaotic motion is that they undergo spatial transport across magnetic field lines. The cross-field diffusion is of interest in a variety of magnetized plasmas including laboratory and astrophysical plasmas.

We perform a self-consistent, time-dependent numerical simulations of dissipative turbulent plasmas at a higher Lundquist number, typically up to O(10(6)), using full three-dimensional compressible magnetohydrodynamics code with a numerical resolution of 128(3). Our simulations follow the time variation of global helicity, magnetic energy, and the dissipation rate and show that the global helicity remains approximately constant, while magnetic energy is decaying faster and the dissipation rate is decaying even faster than the magnetic energy. This establishes that the principle of minimum dissipation rate under the constraint of (approximate) conservation of global helicity is a viable approach for plasma relaxation. (c) 2008 American Institute of Physics.

It has been shown that compared to the KdV soliton the solitary wave solution of the Boussinesq equation gives a closer description of the ion acoustic solitary wave. The salient features of the “dressed KdV soliton” results appear as an approximation to the corresponding results for the solitary wave solution of the Boussinesq equation. A fairly good agreement with present experimental findings is obtained.

The magnetohydrodynamic stability of streaming tearing mode is investigated numerically. A bulk plasma flow parallel to the antiparallel magnetic field lines and localized in the neutral sheet excites a streaming tearing mode more strongly than the usual tearing mode, particularly for the wavelength of the order of the neutral sheet width (or smaller), which is stable for the usual tearing mode. Interestingly, examination of the eigenfunctions of the velocity perturbation and the magnetic field perturbation indicates that the streaming tearing mode carries more energy in terms of the kinetic energy rather than the magnetic energy. This suggests that the streaming tearing mode instability can be a more feasible mechanism of plasma acceleration than the usual tearing mode instability.

We derive for nonequilibrium isotropic plasma the correlations of fluctuation in electric‐field intensity and current density. The calculation is based on the ring‐approximation results of Balescu and Taylor. The results reduce to the results obtained by Rostoker in the special case when the velocity‐distribution function is Maxwellian at the initial time.

The distribution function f of a plasma in a magnetic field consisting of a steady plus an oscillating part has been determined by solving Vlasov’s equation and assuming that the frequency of oscillation is much less than the cyclotron frequency.