Abstract Nonlinear rarefactive isothermal ion-acoustic periodic travelling waves (RIIAPTWs) are examined in a magnetized ultrarelativistic degenerate plasma, containing warm fluid ions and ultrarelativistic degenerate inertialess electrons as well as positrons and immobile heavy negative ions. In the linear regime, the excitation of an isothermal ion-acoustic mode and its evolution are investigated. The physical behavior of nonlinear rarefactive isothermal ion-acoustic waves (RIIAWs) in this plasma model is governed by a Zakharov–Kuznetsov (ZK) equation. The analytical solutions for the nonlinear rarefactive isothermal ion-acoustic solitary waves (RIIASWs) and RIIAPTWs are performed by the bifurcation analysis. A careful discussion demonstrates the excitations of RIIASWs and RIIAPTWs are amplified (i.e., the amplitudes become deeper), as the chemical potential (or the Fermi energy at zero temperature) of electrons is decreased. It is found physically that the presence of the ultrarelativistic degenerate positrons and stationary heavy negative ions have strong effects on features of nonlinear RIIASWs and RIIAPTWs. The implications of the present finding in compact astrophysical objects, such as white dwarf stars, have been discussed.

中文翻译：

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磁化超相对论简并等离子体中的非线性稀有等温离子声波

摘要 在磁化超相对论简并等离子体中研究了非线性稀有等温离子声周期性行波 (RIIAPTW)，该等离子体包含暖流体离子和超相对论简并无惯性电子以及正电子和不动的重负离子。在线性状态下，研究了等温离子声模式的激发及其演变。该等离子体模型中非线性稀有等温离子声波 (RIIAW) 的物理行为由 Zakharov-Kuznetsov (ZK) 方程控制。非线性稀有等温离子声孤立波 (RIIASWs) 和 RIIAPTWs 的解析解由分岔分析执行。仔细讨论表明 RIIASWs 和 RIIAPTWs 的激发被放大（即振幅变深），随着电子的化学势（或零温度下的费米能）降低。物理上发现超相对论简并正电子和静止重负离子的存在对非线性RIIASWs和RIIAPTWs的特征有很强的影响。已经讨论了当前发现对致密天体物理物体（例如白矮星）的影响。