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考虑到内地核较小(其半径为外核的1/3),许多地球发电机模型将内核完全忽略(Hollerbach et al.,1992),要不然就将其处理为不导电的绝缘体(Zhangand Busse,1990;Glatzmaier and Roberts,待出版)。在我们以前的稳态模型(Hollerbach and Jones,1993)中,曾考虑了有限导电内地核的某些效应,尤其是引起内外核之间的电磁耦合效应。本文中,我们包括了一种规定的浮力,从地球物理学的观点讲,这样更加现实,而且所得到的解与时间有关,而不再是与时间无关。在有限导电的内核中的磁场不再是瞬间地调整到外核中的场值,而是有一个它自己固有的几千年的扩散时间尺度。从而外核中较大一些、快一些的地磁涨落有效地被内核平均掉了,产生了相对稳定的外部偶极磁场。我们推测地磁场倒转的发生只能是一次特大的磁场涨落的结果,其幅度足够大,持续时间足够长,使得磁场在整个内核中也发生倒转。
Given the relatively small size of the interior core, which has a radius of 1/3 of the outer core, many earth generator models completely ignore the kernel (Hollerbach et al., 1992) or otherwise treat it as a nonconductive insulator (Zhang and Busse , 1990; Glatzmaier and Roberts, pending publication). In our previous steady-state model (Hollerbach and Jones, 1993), some effects of the finite-conductivity inland nuclei have been considered, especially the electromagnetic coupling effects between the inner and outer nuclei. In this paper, we include a prescribed buoyancy, which is more realistic from a geophysical point of view, and the resulting solution is time dependent, not time-independent. The magnetic field in a finitely conductive core is no longer instantly adjusted to the value in the outer core, but rather has its own inherent diffusion time scale of thousands of years. As a result, the larger and faster geomagnetic fluctuations in the outer core are effectively eliminated by the inner core, resulting in a relatively stable external dipole magnetic field. We speculate that the reversal of the magnetic field can only occur as a result of a large magnetic field that is large enough and long enough to cause the magnetic field to invert throughout the entire kernel.