Mapping and distortions of auroral structures in the quiet magnetosphere
Mapping and distortions of auroral structures in the quiet magnetosphere
复制标题
安静磁层中极光结构的测绘和扭曲
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
Chen Lu
中科院分区：
文献类型：
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作者：
R. Kaufmann;D. Larson;Chen Lu
本报告的目的是确定常见的日间极光特征，这些特征可以通过以下两个过程中的任何一个轻松解释：测绘扭曲或附近伯克兰洋流引起的扭曲。在安静的封闭磁层模型中映射畸变，会在日侧极光区产生非常细长的弧状电离层图像，用于各种圆形或椭圆形管状赤道源。白天极光弧的长度可以很好地测量垂直于磁层顶的赤道源尺寸。日侧弧的方向提供了对太阳磁层 x 赤道源位置的粗略估计。人们发现白天弧和伯克兰电流映射到白天和夜间磁层顶电流层以及低纬度边界层。夜侧极光弧和伯克兰电流映射到磁尾等离子体片和等离子体片边界层。局域伯克兰电流会产生取决于电流密度梯度的特征失真。就安静磁层中的映射扭曲而言，单个和多个线性和钩状极光形式很容易理解。明亮的扭曲或折叠极光形式的形状更容易解释为局部伯克兰电流产生的扭曲。更多» 螺旋极光结构尺寸的测量提供了电流强度的估计。电离层物体的运动与赤道源的运动之间的关系由两个色板总结。这种运动有时与人们的直觉预期明显不同。例如，磁层顶附近的一些向后移动的源可以映射到向太阳移动的电离层图像。 « 更少
The objective of this report is to identify those features of commonly observed dayside auroras that can be explained easily by either of two processes: mapping distortions or distortions caused by nearby Birkeland currents. Mapping distortions in a quiet closed magnetosphere model yield very elongated arclike ionospheric images in the dayside auroral zone for a wide range of circular or elliptical tubelike equatorial sources. The length of a dayside auroral arc provides a good measure of the equatorial source dimension normal to the magnetopause. The orientation of the dayside arc provides a crude estimate of the solar magnetospheric x location of the equatorial source. Dayside arcs and Birkeland currents are found to map to both the dayside and the nightside magnetopause current layer and low latitude boundary layer. Nightside auroral arcs and Birkeland currents map to the magnetotail plasma sheet and plasma sheet boundary layer. Localized Birkeland currents produce characteristic distortions that are dependent on the current density gradient. Single and multiple linear and hooked auroral forms are easy to understand in terms of mapping distortions in a quiet magnetosphere. The shapes of bright twisted or folded auroral forms are more easily explained as distortions produced by localized Birkeland currents.more » Measurement of the size of a spiral auroral structure provides an estimate of the current magnitude. Relationships between the motion of ionospheric objects and the motion of equatorial sources are summarized by two color plates. Such motion sometimes differs markedly from what one might intuitively expect. For example, some tailward moving sources near the magnetopause can map to sunward moving ionospheric images.« less