Numerical simulation of the equatorial plasma bubble: the effect of seeding by the vertical winds and random background noise perturbations.

A wide variety of small-amplitude waves widely exist in the ionosphere and have significant effects on the evolution of equatorial plasma bubbles. In this paper, we simulated equatorial plasma bubbles (EPB) seeded by vertical neutral wind perturbations with wavelengths of 125 km and 250 km, and compared the morphology characteristics of plasma bubble structures with those under random noise perturbations in the background density. The numerical results showed that both vertical winds and random background noise perturbations can contribute to the growth of plasma bubbles, and the perturbations under additional random background noise can promote the growth of the plasma bubble structures faster. Additionally, several processes of the nonlinear behavior of bifurcated EPB structures, including bifurcation, pinching, and small-scale turbulent structures, were successfully obtained. Our simulation captured supersonic flows within the low-density plasma structures characterized by vertical velocities of about 1.5 km/s, which is consistent with experimental studies found in the literature.电离层中广泛存在多种小振幅波动，且此类波动对赤道等离子体泡（equatorial plasma bubbles, EPB）的演化具有显著影响。本文针对波长分别为125 km与250 km的垂直中性风扰动激发的赤道等离子体泡开展数值模拟，并将等离子体泡结构的形态特征与背景密度受随机噪声扰动时的情况进行了对比。数值模拟结果表明，垂直风扰动与背景随机噪声扰动均可促进等离子体泡的增长，且额外叠加的背景随机噪声扰动能够更快地推动等离子体泡结构的生长。此外，本文成功复现了分叉型赤道等离子体泡非线性演化的若干过程，包括分叉、缩颈以及小尺度湍流结构的形成。本次模拟捕捉到低密度等离子体结构内的超声速流动，其垂直速度约为1.5 km/s，这一结果与已有文献报道的实验研究结论一致。