电离层重力电流与压力梯度电流的模拟研究

Simulation study of ionospheric gravity currents and pressure gradient currents

风场发电机驱动产生电离层电流,其主要分布在日侧E区.电离层电流会产生显著的地磁扰动,这也是地磁静日(Solar quiet,S_(q))变化的主要来源.但是,电离层区域的其他作用力,包括等离子体重力和压力梯度力,同样能驱动等离子体跨越磁力线,进而影响了电离层电流.本文首先探讨了等离子体重力和压力梯度力在电离层发电机过程中的作用机制,随后利用数值模拟得到重力电流和压力梯度电流.通过分析重力电流和压力梯度电流的时空分布,我们发现它们的分布区域与电离层赤道异常(EIA)重合,重力电流方向是地磁东向的,而压力梯度电流在EIA结构的底部是东向的而顶部是西向的.除此之外,我们发现重力和压力梯度电流的经度分布受到地磁场和潮汐的影响,其中电流强度与磁场强度反相关.

Ionospheric currents are primarily driven by the neutral wind dynamo, predominantly distributed in the dayside E region. Ionospheric currents can generate obvious geomagnetic disturbances, which are the main sources of Solar-quiet (S_(q)) geomagnetic variations. However, there are other forces in the ionosphere, including plasma weight forces and pressure gradient forces, which can also drive the plasma across magnetic field lines and affect ionospheric currents and geomagnetic perturbations. In this paper, we first investigated the mechanisms of plasma gravity and pressure gradient forces in the ionospheric dynamo, and then acquired the gravity currents and pressure gradient currents through numerical simulations. The analysis of the spatiotemporal distribution of gravity current and pressure gradient current revealed that their distribution regions coincided with those of the Equatorial Ionospheric Anomaly (EIA). The gravity current flows eastward in the geomagnetic field, while the pressure gradient current flows eastward at the bottom of the EIA and westward at the top of the EIA. Additionally, the longitudinal distribution of gravity and pressure gradient currents was influenced by the geomagnetic field and tides. The current strength inversely correlated with that of the magnetic field.