Solitary kinetic Alfvén waves in the two-fluid model

Abstract

Employing the two-fluid model, a generalized Sagdeev equation governing solitary kinetic Alfvén waves (SKAWs) and the criterion for the existence of SKAWs, which are valid for different ranges of plasma pressure parameter β, are presented. In the limit cases of β≫me/mi and β≪me/mi, the present results correspond, respectively, with conclusions obtained by Hasegawa et al. [Phys. Rev. Lett. 37, 690 (1976)] and by Shukla et al. [J. Plasma Phys. 28, 125 (1982)], that is, SKAWs accompanied by, respectively, hump and dip density solitons for β≫me/mi and β≪me/mi. However, for the case of β∼me/mi, the present results show that SKAWs accompanied by both hump and dip density solitons are possible, and lead to KdV solitons in the small amplitude limit. In addition, the possibility for applying these results to electromagnetic spikes observed by the Freja scientific satellite is discussed [detailed information about the Freja satellite experiments can be found in serial papers presented in Space Sci. Rev. 70, Nos. 3/4 (1994)].

Alfvén waves in space and astrophysical dusty plasmas

“…The wave-particle interaction in KAWs depends sensitively on the plasma β parameter (Wu et al, 1996). Hasegawa and Cheng (1976) showed that in a low beta plasma 1 > β > m e /m i , the wave is weakly damped due to ion Landau damping leading to ion heating (Hasegawa and Cheng, 1976), whereas if electron temperature is comparable to ion temperature, nonlinear Landau damping occurs.…”

“…Zhao et al (2011) discussed the damping mechanism of KAWs in the dense plume structure of coronal holes and showed that KAWs are strongly damped in this region due to Landau damping when λ e k ⊥ < 0.3. Wu and Fang (1999 and Wu et al (1996) showed that the parallel electric field of the KAW can lead to effective electron heating due to kinetic damping or Ohmic dissipation, which can further dissipate the KAW energy to sustain the temperature of the coronal loop plasmas. This dissipation occurs due to the parallel electric field of the KAW, which helps the local electron heating and acceleration mechanism to balance the additional radiative loss of the bright plume.…”

Anisotropic and mass-dependent energization of heavy ions by kinetic Alfvén waves

“…In a three-component plasma (electrons, protons, and heavy ions) magnetized by a magnetic field B 0 along the z axis, the equation set governing the dynamics of KAWs consists of the following (Wu et al 1995(Wu et al , 1996Wu & Chao 2004b): (i) the continuity equations of electrons, protons, and heavy ions…”

Recent progress in nonlinear kinetic Alfvén waves

“…Wu et al (1995) first derived an exactly analytical solution of SKAWs with an arbitrary amplitude in a low-β plasma with β/2 Q. Taking the cold ion approximation of T i T e , Wu et al (1996b) extended the works of Hasegawa and Mima (1976) (for α 1) and Shukla et al (1982) (for α 1) to more general ranges for the parameter α and took account of both the electron temperature and inertia terms simultaneously. They obtained a generalized Sagdeev equation and found a general criterion for the existence of SKAWs.…”