Nonlinear Fluid Models for Electrostatic Solitary Waves Observed in Space Plasmas
Abstract
Nonlinear fluid models for the ion- and electron-acoustic solitons and double layers in multi-component magnetized plasmas are proposed for the electrostatic solitary waves (ESWs) observed in the Earth's magnetosphere, solar wind and in the Lunar wake. The ESWs are found in the electric field parallel to the background magnetic field, and are usually bipolar or tripolar. The space plasmas are modelled by a combination of various plasma species, e.g., fluid hot protons, hot alpha particles streaming with respect to protons, back ground electrons or electron beams and suprathermal electrons having -distribution. The four component plasma system consisting of two ion species and two electron species can support two types of, slow and fast, ion-acoustic solitary waves/double layers and an electron-acoustic solitary waves. The fast ion-acoustic mode is similar to the ion-acoustic mode of proton-electron plasma, and it can support only positive potential solitons. The slow ion-acoustic mode is a new mode that occurs due to the presence of alpha particles. This mode can support both positive and negative solitons and double layers. The electron-acoustic mode occurs in presence of two electron (hot and cold) species. It can support either negative or positive solitons and double layers. The relationship between the predictions of theoretical models and space observations of ESWs will be discussed for a few specific cases, e.g., coherent electrostatic waves observed in the solar wind, Lunar wake and in the plasma sheet boundary layer. It will be shown that models based on ion- and electron-acoustic solitons/double layers provide a plausible interpretation for the ESWs observed in space plasmas.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1112S