11 Magnetic Tempests
地球物理学：介绍当前关于地球磁场风暴和磁场移动的研究
导读
磁暴是当太阳表面活动旺盛，特别是在太阳黑子极大期时，太阳表面的闪焰爆发次数也会增加，闪焰爆发时会辐射出X射线、紫外线、可见光及高能量的质子和电子束。其中的带电粒子（质子、电子）形成的电流冲击地球磁场，引发短波通信称磁暴。磁暴时会增强大气中电离层的游离化，也会使极区的极光特别绚丽，另外还会产生杂音掩盖通信时的正常信号，甚至使通信中断，也可能使高压电线产生瞬间超高压，造成电力中断，也会对航空器造成伤害。
The Earth's magnetic field is generated as the molten iron of the Earth's outer core revolves around its solid inner core. When surges in the molten iron occur, magnetic tempests are created. At the Earth's surface, these tempests can be detected by changes in the strength of the Earth's magnetic field. For reasons not fully understood, the field itself reverses periodically every million years or so. During the past million years, for instance, the magnetic north pole has migrated between the Antarctic and the Arctic.
Clearly, geophysicists who seek to explain and forecast changes in the field must understand what happens in the outer core. Unlike meteorologists, however, they cannot rely on observations made in their own lifetimes. Whereas atmospheric storms arise in a matter of hours and last for days, magnetic tempests develop over decades and persist for centuries. Fortunately scientists have been recording changes in the Earth's magnetic field for more than 300 years.
地球磁场是由于地球外核熔融的铁围绕其固体的内核旋转而产生的。当熔融的铁发生浪涌时，就引起磁场风暴。在地球表面，磁场风暴可以根据地球磁场强度的变化来加以测定。由于尚未完全弄清楚的原因，地球磁场每百万年周期地发生倒转。例如，在过去的百万年中，磁场北极在地球南北极之间发生了移动。
显然，试图解释和预测地球磁场变化的地球物理学家必须理解地球外核所发生的事情。然而，跟气象学家不同，为了这个目的，他们不可能只指望他们本人有生之年所得到的观察资料。大气风暴的发生是几小时之内的事情，其持续时间也不过几天；而地球磁场风暴的发生要经过几十年，其持续时间要达数世纪之久。幸运的是，科学家记录磁场的变化已经有了三百年的历史。
Sentence Translation
句子翻译
1. When surges in the molten iron occur, magnetic tempests are created. At the Earth's surface, these tempests can be detected by changes in the strength of the Earth's magnetic field.
2. Whereas atmospheric storms arise in a matter of hours and last for days, magnetic tempests develop over decades and persist for centuries.
Key
1．当熔融的铁发生浪涌时，就引起磁场风暴。在地球表面，磁场风暴可以根据地球磁场强度的变化来加以测定。
2．大气风暴的发生是几小时之内的事情，其持续时间也不过几天；而地球磁场风暴的发生要经过几十年，其持续时间要达数世纪之久。