Simulation of ion-cyclotron-like modes in a magnetoplasma with transverse inhomogeneous electric field

Abstract

Ion-cyclotron turbulence has been observed with shocks and double layers in the magnetosphere where strongly localized electric fields perpendicular to the magnetic field are present. Theoretical analysis suggests that electrostatic waves with frequencies of the order of the ion-cyclotron frequency can be destabilized as a result of the coupling of regions of positive and negative-energy ion waves. The nonlocal theory for a smooth profile of transverse inhomogeneous electric fields shows that localized ion waves grow in the region where the electric fields are present. Using a spatially two-dimensional electrostatic code, we investigate this instability in plasma conditions characterized by a localized transverse electric field L≪Lx, where Lx is the simulation length in the x direction; and distinguish it from the transverse kinetic Kelvin–Helmholtz instability. The simulation results show that the growing ion waves are associated with the small vortices in the linear state, which evolve into a nonlinear stage dominated by large vortices with lower frequencies.

Experimental verification of the inhomogeneous energy-density driven instability

“…Spectra corresponding to the two modes are shown as insets in Fig. 3 shapes, single peaked and narrow band (FWHM= 2.5 kHz, or 3%) for CDEIC waves and spiky and broad band (FWHM = 12 kHz, or 16%) for IEDD waves, consistent with the simulations of Nishikawa et al [19]. Frequencies below the potassium-cyclotron frequency are occasionally seen for these IEDD waves.…”

Kinetic effects on the Kelvin–Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations

“…The three-dimensional effects are also believed to be important from the kinetic aspect; Nishikawa et al 21 have shown that the component of the KH k-vector in the Z-direction ͑parallel to the magnetic field͒ tends to largely reduce the growth rate of the KHI, and hence the ion-cyclotron modes can dominate the KHI. Thus, threedimensional effects should not be neglected in considering the kinetic properties of the KHI and associated vortex structure.…”

“…13,21,22 Here, V 0 Ј͑Y͒ =dV 0 ͑Y͒ / dY. In the strong shear case, the strong convective electric field can produce a complex but kinetically rather stable equilibrium of the velocity shear layer as shown in Sec.…”

Parallel Flow Velocity Shear Kelvin Helmholtz Instability With Ac Electric Field

“…Ganguli et al [2][3][4] show that such a situation also gives rise to instabilities. Electrostatic particle simulation has also been employed to reveal more fully the character of the instability in the ion cyclotron regime [5,6]. Pritchett and Coroniti [7,8] have carried out similar simulation for the longer wavelength electrostatic Kelvin Helmholtz instability, showing reduction of growth when the ion gyroradius becomes comparable to the shear layer thickness.…”