Fluid models for kinetic effects on coherent nonlinear Alfvén waves. I. Fundamental theory

Abstract. Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs) in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field) protons. The ion acceleration is associated with the dissipation of phasesteepened Alfvén waves, presumably through the Ponderomotive Force. Proton perpendicular heating, through instabilities, lead to the generation of both proton cyclotron waves and mirror mode structures. Electromagnetic and electrostatic electron waves are detected as well. The Alfvén waves are thus found to be both dispersive and dissipative, conditions indicting that they may be intermediate shocks. The resultant "turbulence" created by the Alfvén wave dissipation is quite complex. There are both propagating (waves) and nonpropagating (mirror mode structures and MDs) byproducts. Arguments are presented to indicate that similar processes associated with Alfvén waves are occurring in the magnetosphere. In the magnetosphere, the "turbulence" is even further complicated by the damping of obliquely propagating proton cyclotron waves and the formation of electron holes, a form of solitary waves. Interplanetary Alfvén waves are shown to rapidly phase-steepen at a distance of 1 AU from the Sun. A steepening rate of ∼35 times per wavelength is indicated by Cluster-ACE measurements. Interplanetary (reverse) shock compression of Alfvén waves is noted to cause the rapid formation of MDs on the sunwardCorrespondence to: B. T. Tsurutani (bruce.tsurutani@jpl.nasa.gov) side of corotating interaction regions (CIRs). Although much has been learned about the Alfvén wave phase-steepening processfrom space plasma observations, many facets are still not understood. Several of these topics are discussed for the interested researcher. Computer simulations and theoretical developments will be particularly useful in making further progress in this exciting new area.

Section: Final Commentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?

Tsurutani

Lakhina

Pickett

et al. 2005

“…Khabibrakhmanov et al (1993) developed a model of collisionless parallel shock based on a modified DNLS by including the anisotropy of the plasma distribution function and higher-order dispersion; the number of adiabatically reflected ions define the threshold conditions of the fire-hose and mirror-type instabilities in the upstream and downstream regions of the shock. Medvedev and Diamond (1996) modeled the kinetic resonant particle effects of nonlinear Alfvén waves by incorporating an additional term representing dissipation akin to parallel heat conduction in a modified DNLS, which removes the singularity usually encountered in the nonlinear terms of DNLS and takes into account nonlinear coupling of an Alfvénic mode to a kinetic ion-acoustic mode; damping of nonlinear Alfvén waves appears via a strong Landau damping of the ion-acoustic waves. Baumgartel (1999) applied the magnetically rarefactive (dark) MHD soliton solution of DNLS to explain magnetic holes observed in solar wind, planetary magnetosheath and cometary environment.…”

Section: Derivative Nonlinear Schrödinger Equationmentioning

confidence: 99%

Chaos in driven Alfvén systems: unstable periodic orbits and chaotic saddles

Chian

Santana

Rempel

et al. 2007

Abstract. The chaotic dynamics of Alfvén waves in space plasmas governed by the derivative nonlinear Schrödinger equation, in the low-dimensional limit described by stationary spatial solutions, is studied. A bifurcation diagram is constructed, by varying the driver amplitude, to identify a number of nonlinear dynamical processes including saddlenode bifurcation, boundary crisis, and interior crisis. The roles played by unstable periodic orbits and chaotic saddles in these transitions are analyzed, and the conversion from a chaotic saddle to a chaotic attractor in these dynamical processes is demonstrated. In particular, the phenomenon of gap-filling in the chaotic transition from weak chaos to strong chaos via an interior crisis is investigated. A coupling unstable periodic orbit created by an explosion, within the gaps of the chaotic saddles embedded in a chaotic attractor following an interior crisis, is found numerically. The gapfilling unstable periodic orbits are responsible for coupling the banded chaotic saddle (BCS) to the surrounding chaotic saddle (SCS), leading to crisis-induced intermittency. The physical relevance of chaos for Alfvén intermittent turbulence observed in the solar wind is discussed.

“…Solitons in the magnetoplasma were studied theoretically using Derivative Nonlinear Schrödinger (DNSL) equation by several authors (Hada et al, 1989;Mjølhus and Wyller, 1988;Spangler, 1990;Medvedev and Diamond, 1996;Nocera and Buti, 1996;Buti, 1999;Passot et al, 2005) The solutions concerned mainly circularly polarized waves propagating parallel to the magnetic field. Another development concerned quasi-perpendicular propagation of dispersive Alfvén waves and processes leading to establishment of filamentary structures with small size perpendicular to B (e.g.…”

Section: Other Theoretical Models For Dispersive Alfvén Waves and Solmentioning

confidence: 99%

“…Alfvénic soliton solutions have been studied extensively using Derivative Nonlinear Schrödinger (DNSL) equation (Hada et al, 1989;Medvedev and Diamond, 1996;Mjølhus and Wyller, 1988;Nocera and Buti, 1996;Spangler, 1990;Buti, 1999;Passot et al, 2005), or complete one-or two-fluid equations (McKenzie et al, 2004;Dubinin et al, 2003Dubinin et al, , 2005Sauer et al, 2003). However, until recently it has not been realized that soliton solutions represent bipolar electric field structures with either positive Published by Copernicus Publications on behalf of the European Geosciences Union and the American Geophysical Union.…”

Section: Introductionmentioning

confidence: 99%

Dispersive MHD waves and alfvenons in charge non-neutral plasmas

Stasiewicz

Ekeberg

2008

Abstract. Dispersive properties of linear and nonlinear MHD waves, including shear, kinetic, electron inertial Alfvén, and slow and fast magnetosonic waves are analyzed using both analytical expansions and a novel technique of dispersion diagrams. The analysis is extended to explicitly include space charge effects in non-neutral plasmas. Nonlinear soliton solutions, here called alfvenons, are found to represent either convergent or divergent electric field structures with electric potentials and spatial dimensions similar to those observed by satellites in auroral regions. Similar solitary structures are postulated to be created in the solar corona, where fast alfvenons can provide acceleration of electrons to hundreds of keV during flares. Slow alfvenons driven by chromospheric convection produce positive potentials that can account for the acceleration of solar wind ions to 300-800 km/s. New results are discussed in the context of observations and other theoretical models for nonlinear Alfvén waves in space plasmas.