Rotationally driven ‘zebra stripes’ in Earth’s inner radiation belt
Rotationally driven ‘zebra stripes’ in Earth’s inner radiation belt
复制标题
地球内部辐射带中旋转驱动的“斑马条纹”
作者：
A. Ukhorskiy;M. Sitnov;D. Mitchell;K. Takahashi;L. Lanzerotti;B. Mauk
地球上辐射带粒子名义上均匀分布的结构特征以前一直与粒子加速和传输机制有关，这些机制完全由增强的太阳风活动提供动力。虽然行星自转被认为对木星和土星的粒子加速很重要，但地球自转在内磁层产生的电场只能改变被捕获粒子的速度约为每秒1-2公里，因此自转对于速度约为每秒10万公里的辐射带电子来说是无关紧要的。在这里，我们报告了高能电子在整个地球内辐射带空间范围内的分布是以规则的、高度结构化的和意想不到的“斑马线”组织的，即使在太阳风活动较低的情况下也是如此。模型显示，这些图案是由地球自转产生的。辐射带电子被困在类偶极磁场中，由于磁场的梯度和曲率，它们在地球上经历缓慢的纵向漂移运动。地球自转引起了磁场和电场的全球日变化，这些磁场和电场与漂移周期接近24小时的电子发生共振相互作用，将广泛能量范围内的电子通量改变为由跨越整个内辐射带的多条条纹组成的规则模式。
Structured features on top of nominally smooth distributions of radiation-belt particles at Earth have been previously associated with particle acceleration and transport mechanisms powered exclusively by enhanced solar-wind activity. Although planetary rotation is considered to be important for particle acceleration at Jupiter and Saturn, the electric field produced in the inner magnetosphere by Earth’s rotation can change the velocity of trapped particles by only about 1–2 kilometres per second, so rotation has been thought inconsequential for radiation-belt electrons with velocities of about 100,000 kilometres per second. Here we report that the distributions of energetic electrons across the entire spatial extent of Earth’s inner radiation belt are organized in regular, highly structured and unexpected ‘zebra stripes’, even when the solar-wind activity is low. Modelling reveals that the patterns are produced by Earth’s rotation. Radiation-belt electrons are trapped in Earth’s dipole-like magnetic field, where they undergo slow longitudinal drift motion around the planet because of the gradient and curvature of the magnetic field. Earth’s rotation induces global diurnal variations of magnetic and electric fields that resonantly interact with electrons whose drift period is close to 24 hours, modifying electron fluxes over a broad energy range into regular patterns composed of multiple stripes extending over the entire span of the inner radiation belt.
来自卡西尼-惠更斯号的土星
DOI：
10.1007/978-1-4020-9217-6_12
发表时间：
2009
期刊：
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影响因子：
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作者：
Kurth W
通讯作者：
Kurth W