Role of ion thermal velocity in the formation and dynamics of electrostatic solitary waves in plasmas

Abstract

We perform fluid simulations to examine the effect of ion thermal velocity on the formation and dynamics of solitary waves in an unmagnetized two-component plasma consisting of ions and electrons. Based on the linear and nonlinear fluid theories, some of the previous studies have reported that the plasma with the electron temperature greater than the ion temperature (i.e., Te > Ti) supports ion acoustic solitary waves (IASWs), whereas the plasma with Te ≪ Ti supports electron acoustic waves (EASWs). In this paper, we have considered a wide range of ion temperatures (with fixed electron temperature) to examine the criteria of temperature and thermal velocities in the generation of EASWs and IASWs in plasmas. Our simulation shows that the plasma with Ti > Te possesses two wave modes depending on the ratio of its thermal velocities. When the ratio of electron to ion thermal velocities R = Vthe/Vthi > 1, the system supports the generation of IASWs, whereas for R < 1, it supports the generation of EASWs. The analysis of characteristics like the amplitude, width, and phase speed of these solitary waves implies that the EASWs have a negative potential, whereas the IASWs have the positive potential. The transition from IASWs to EASWs occurs when the phase speed of the solitary wave exceeds the limiting value of 3Vthe. This simulation study presents the detailed investigation of the evolution of EASWs and IASWs generated in plasmas having Ti > Te, which will have implications in modeling such waves in space and laboratory plasmas.

Debye-scale Solitary Structures in the Martian Magnetosheath

“…BEN consist of a series of electrostatic solitary waves (ESWs) and their characteristics are determined by the ambient plasma population therein. These electric field structures are generally bipolar in nature, and they are identified as ion/electron acoustic waves or as electron/ion phase-space holes (Omura et al 1996;Lakhina et al 2011;Kakad et al 2019;Pickett 2021). Observations of solitary wave structures are not limited to Earth; they are also observed in other planetary magnetospheres (Williams et al 2006;Malaspina et al 2020), and astrophysical plasma environments (Tao et al 2012;Mozer et al 2021aMozer et al , 2021b.…”

Formation of Asymmetric Electron Acoustic Double Layers in the Earth's Inner Magnetosphere

“…n s , v s , and p s are density, velocity, and pressure of the species s, respectively. In such a case, the choice of = 3 appears to be appropriate as particles have essentially 1 degree of freedom along the wave propagation direction (Kakad et al, 2019). Here, is an adiabatic index, which is in general considered to be equal to one for hot electrons [Sagdeev, 1966].…”

“…In this study, we have assumed the same adiabatic equation of state with = 3 for all the species as we deal with the one-dimensional plasma system. In such a case, the choice of = 3 appears to be appropriate as particles have essentially 1 degree of freedom along the wave propagation direction (Kakad et al, 2019). In such a case, the equations above are coupled with the following Poisson's equation…”

“…In the development of the fluid code, equations ( 1)-(4) were solved by using numerical schemes discussed in Kakad et al (2013Kakad et al ( , 2014Kakad et al ( , 2019 and . The fluid simulation was performed in a one-dimensional system with periodic boundary conditions.…”

The Nonlinear Magnetosonic Waves in Magnetized Dense Plasma for Quantum Effects of Degenerate Electrons

“…The QHD was used to investigate the quantum magnetosonic waves and a deformed Korteweg-de Vries (KdV) equation was derived by Haas et al [7]. In classical plasma, the KdV equation is well known for the small but limited amplitude of ionic sound wave [8], [9]. Both degenerate (without spin) and non-degenerate (with spin) quantum plasmas were studied respectively by using small amplitude limited perturbation scheme obliquely two-dimensional nonlinear magnetosonic waves [10 -11].…”