Role of variability in determining the vertical wind speeds and structure
Role of variability in determining the vertical wind speeds and structure
复制标题
变异性在确定垂直风速和结构中的作用
DOI：
10.1029/2011ja016714
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发表时间：
2011
影响因子：
--
通讯作者：
A. Ridley
中科院分区：
文献类型：
--
作者：
Erdal Yiğit;A. Ridley
[1]密歇根大学的全球电离层热层模式（GITM）被用来研究在冬至期间高纬度垂直风的时间和空间变化。在一系列系统的模式模拟中研究了控制热层中高纬度分布和垂直风大小的潜在机制。首先，在一系列六个模型模拟中，GITM经度×纬度分辨率从5° × 5°逐渐增加到2.5° × 0.3125°，在所有模拟中施加恒定的中等太阳和低磁层活动。高纬度的平均参数的分析表明，垂直风和焦耳加热的极地分布表现出本地化的增强，在高空间分辨率，粗网格分辨率没有很好地捕捉。其次，在2.5° × 2.5°固定空间分辨率的模拟中，研究了随时间变化的磁层条件对高纬垂直风形态的影响。为此，半球功率和跨极冠电位值进行了修改，在一系列系统的模拟。离子流的大小和时间变化对高纬焦耳加热有显著的影响，而焦耳加热又显著影响垂直风场结构。它表明，在垂直风的变化是由离子流的变化和离子流的突然的阶梯状变化，可以导致最大的增强垂直风，特别是通过非流体静力学效应。垂直风变率被认为是最大的夏季南半球与更大的垂直风量级。
[1] The University of Michigan's Global Ionosphere Thermosphere Model (GITM) is used to study the temporal and spatial variability of high-latitude vertical winds during the December solstice. Underlying mechanisms controlling the high-latitude distribution and the magnitude of vertical winds in the thermosphere are investigated in a suite of systematic model simulations. First, in a series of six model simulations GITM longitude × latitude resolution is gradually increased from 5° × 5° to 2.5° × 0.3125°, imposing constant moderate solar and low magnetospheric activity in all simulations. Analysis of the high-latitude mean parameters shows that polar distributions of vertical winds and Joule heating demonstrate localized enhancements at high spatial resolution that are not well captured at coarse grid resolution. Second, in simulations with fixed spatial resolution of 2.5° × 2.5°, the impact of temporally variable magnetospheric conditions on the morphology of the high-latitude vertical winds has been investigated. For this, hemispheric power and the cross polar cap potential values are modified in a series of systematic simulations. The magnitude and temporal variations of ion flows significantly impact the high-latitude Joule heating, which in turn dramatically effects the vertical wind structure. It is demonstrated that variability in the vertical winds are driven by variability in the ion flows and that sudden step-like changes in ion flows can cause the largest enhancements in the vertical winds, in particular, via nonhydrostatic effects. The vertical wind variability is seen to be the largest in the summer Southern Hemisphere with much larger vertical wind magnitudes.