Propagation of nonlinear ion-acoustic fluctuations in the mantle of Venus

¹ Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA
² Institut für Theoretische Physik IV, Ruhr-Universität Bochum, 44780 Bochum, Germany
e-mail: Alaa.Fayad@ruhr-uni-bochum.de
³ Department of Physics, Faculty of Science, Port Said University, Port Said 42521, Egypt
⁴ Centre for Theoretical Physics, The British University in Egypt (BUE), El-Shorouk City, Cairo, Egypt
⁵ Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium

Received: 20 November 2023
Accepted: 15 February 2024

Abstract

Motivated by the observations of ion-acoustic fluctuations with the Parker Solar Probe (PSP) and earlier by the Pioneer Venus Orbiter (PVO) in the Venusian magnetosheath, we investigate the nature of ion-acoustic solitary and double-layer (DL) structures in the mantle. We employed a hydrodynamic description along with reductive perturbation theory to derive the nonlinear Zakharov—Kuznetsov equation that elucidates the dynamics of three-dimensional ion-acoustic wave packets. Using the spacecraft measurements of the plasma configuration at Venus, we carried out a parametric analysis of these structures, including the influence of the magnetic field strength and the relative densities and temperatures, considering two cases: quasi-parallel and oblique propagation. Moreover, we determined the structural characteristics of these waves, where oblique (quasi-parallel) solitary waves have a potential of 0.4 V (0.4 V) and a maximum electric field amplitude E_m ~ 0.024 mV m⁻¹ (8 m V m⁻¹) across spatial and temporal widths of ~40–80 km (~140–200 m) and 0.4 s (1.6 ms). These waves produce low-frequency electrostatic activity in the frequency range of 1.6–10 Hz (630–3160 Hz). Quasi-parallel DLs have potential drops of (6.5–13) V and E_m ~ (0.16–0.35) mV m⁻¹ with a width and duration of (100–120) m and ~1 ms, and a frequency range of ~630–3980 Hz. These outcomes can explain the detected electrostatic fluctuations above the ionosphere via PVO in the frequency channels of 730 Hz and 5.4 kHz. Furthermore, the DL features estimated in this work are in line with the recent PSP measurements of the DLs propagating in the magnetosheath of Venus.