Existence domains of electrostatic solitary structures in the solar wind plasma

Abstract

Electrostatic solitary waves and double layers are explored in a homogeneous, collisionless, and magnetized three-component plasma composed of hot protons, hot heavier ions (alpha particles, He++), and suprathermal electrons with kappa distribution. The Sagdeev pseudopotential technique is used to study the arbitrary amplitude ion-acoustic solitons and double layers. The effect of various parameters such as the number density of ions, ni0; the spectral index, κ; the Mach numbers, M; and the temperature ratio of ion to the electron σi on the evolution of ion-acoustic solitary waves as well as their existence domains is studied. The transition in the existence domain for slow-ion acoustic solitons from negative solitons/double layers to positive solitons/double layers is found to occur with a variation of the heavier ion temperature. It is observed that the width of the negative potential solitons increases as the amplitude increases, whereas for the positive potential solitons, the width decreases as the amplitude increases. Furthermore, it is found that the limitation on the attainable amplitudes of fast ion-acoustic solitons is attributed to that the number density of protons should remain real valued, while for the slow ion-acoustic solitons, the upper limit is provided by the requirement that the number density of heavier ions should remain real. In the presence of a double layer, the occurrence of the double layer limits the attainable amplitudes of the slow ion-acoustic solitons. The proposed plasma model is relevant to the coherent electrostatic structures observed in the solar wind at 1 AU.