地球内核与地球深部动力学

地球内核由外核富含铁元素的液态物质结晶而成。经证实，内核正以约１（°）／ａ的速率相对于地幔向东转动。内核的旋转是通过穿过内核的地震波的走时随时间变化推测得到的。这种变化是最近十多年来揭示出的内核各向异性在空间方位的改变所造成。内核的各向异性被认为起因于各向异性的铁晶体的有序排列，但这种有序排列的机制还不清楚。内核在地球发电机中起着重要的作用。利用大型的并行计算机，人们已得到能产生像地磁场一样的三维发电机数值模拟。地震学观测到的内核差速旋转为最近的发电机数值模拟提供了支持。这种数值模拟曾预测：导体内核与外核产生的磁场的电磁耦合驱动了内核每年几度向东旋转。地核通过核幔边界的接触及内核与地幔的引力耦合与地幔存在强烈的相互作用。多学科领域的突破为认识地球的深部动力过程提供了极好的机会和手段。

THE EARTH'S INNER CORE AND THE DYNAMICS OF THE EARTH'S DEEP INTERIOR

The Earth's solid inner core was formed by the freezing of iron rich liquid materials making up the outer core. The inner core was shown to be rotating relative to the mantle with an estimated rate of rotation of 1(°)/a eastwards. The inner core rotation is inferred from seismic observations of temporal variations of inner core travel times caused by the changes of the orientation of the inner core anisotropy established in the recent decade. The anisotropy is believed to be due to a preferred orientation of anisotropic iron crystals composing the inner core, but the mechanisms responsible for creating such a preferred orientation remain uncertain. The inner core plays important roles in the dynamo. Using massive parallel computers, three dimensional numerical simulations of the dynamo have been made, which generate Earth like magnetic fields. The observed inner core rotation supports the recent numerical modeling of the dynamo, which predicts that the inner core is driven to rotate eastward a few degrees per year by the magnetic coupling between the electrically conductive inner core and the magnetic field generated in the fluid core. The Earth's core interacts strongly with the mantle through the contact at the core mantle boundary and through the gravitational coupling between the inner core and the mantle. The multidisciplinary breakthroughs present a major opportunity in understanding the dynamics at the deep interior of the Earth.