标题： 大尺度磁场的起源 显示英文标题

标题： The origin of large scale magnetic fields

摘要： 在旋涡星系中可以看到尺度达数千秒差距的相关磁场。这些磁场的起源可能是原始宇宙学场的缠绕，或者是由微小种子场通过星系湍流发电机效应放大所致。这两种可能性都存在困难：目前尚无已知的电池机制可以产生所需的原始磁场。同样地，由于过量的小尺度功率生成，湍流发电机可能在能够产生大尺度磁场之前就自行破坏了。讨论了这些困难的现状。解决这些问题可能取决于由小尺度发电机产生的饱和场的性质。我们论证了小尺度场并不占据流体的大部分体积，而是集中在间歇性的绳状结构中，其峰值值约为等离子场，并且半径远小于它们的长度。在这种情况下，这些场既不会从湍流中耗散大量能量，也不会将湍流在外尺度上的涡动转化为波动。这保留了大规模发电机操作所需的扩散效应。 显示英文摘要

摘要： Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale to wave like motion. This preserves the diffusive effects needed for the large scale dynamo operation.