Instability of obliquely propagating electron acoustic waves in dayside auroral zone plasma with cold electron fluid and vortex-like hot electron distribution

Electron acoustic solitary waves (EASWs) play a crucial role in understanding nonlinear structures observed in the dayside auroral plasma. In this work, we present a comprehensive theoretical analysis of the nonlinear propagation and instability of EASWs in a magnetized auroral plasma composed of stationary ions, cold electron fluid, an electron beam, and hot electrons characterized by a vortex-like distribution. Using the reductive perturbation method, we derive a modified Zakharov–Kuznetsov equation governing the evolution of obliquely propagating EASWs. The derived soliton solution exhibits a distinct profile proportional to sec h4(ϖZ), in contrast to the sec h2(ϖZ) profile previously reported for nonthermal hot electron distributions. This difference highlights the strong influence of the vortex-like hot electron distribution on the nonlinear wave dynamics. A detailed parametric investigation shows that the soliton amplitude and width decrease with increasing hot electron distribution parameter |β|, density ratio ρ, and temperature ratio σ. The external magnetic field ω modifies only the soliton width, while the obliqueness angle δ enhances the amplitude and compresses the width beyond a critical value. The analysis further confirms that the system consistently supports positive-potential EASWs across all physically relevant parameter regimes. Overall, the study demonstrates how hot electron distribution significantly alters the nonlinear characteristics of EASWs, offering new insights into wave behavior in auroral plasmas and contributing to a deeper understanding of space plasma dynamics.