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

Abstract

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.

Solar wind vs magnetosheath turbulence and Alfvén vortices

“…2 A discussion about small scale discontinuities (on kinetic scales) induced by the steepening of large scale Alfvén waves, with wavelengths ∼0.01 AU, can be found in (Tsurutani et al, 2005); a possible relationship between the small scale solar wind discontinuities and the Alfvénic turbulent fluctuations has been recently reported in (Vasquez et al, 2007). and there are no phase correlations between the waves. On the contrary, the turbulence described by a Kolmogorov-like phenomenology refers to strong turbulence, where the fluctuations exchange energy in times of the order of their life time.…”

Ondas de Alfvén no meio interplanetário

“…(10), a velocidade de propagação depende do campo magnético e da densidade de partículas do meio. Por exemplo, a velocidade de fase dessas ondas próximo ao Solé extremamente alta (≈ 1200 km s −1 a cerca de 4 raios solares) se comparadaà velocidade naórbita da Terra queé de aproximadamente 50-70 km s −1 [12]. …”

“…Porém, algumas indicações já foram descobertas sobre o assunto. Uma das formas de amortecimento das ondas de Alfvéné o espalhamento de partículas, onde a ondaé amortecida ao ceder parte de sua energiaàs partículas [12,20]. Porém, muito pouco se sabe sobre os detalhes dessas interações ondas-partículas.…”

“…Essa força está associada aos gradientes de campo da onda [12]. Porém, ainda não existem confirmações de que esse seja realmente o processo decisivo para o amortecimento das ondas.…”

Structure of a Magnetic Decrease Observed in a Corotating Interaction Region

“…Buti et al (2001) proposed large-amplitude Alfvén wave packets can evolve into the magnetic holes or decreases. Phase-steepened nonlinear Alfvén waves have also been suggested as the origin of the magnetic holes or deCorresponding author: E. Lee creases (Tsurutani et al 2002a(Tsurutani et al ,b, 2005aTsubouchi 2009). However, the formation mechanism is not fully understood yet.…”