At the Earth's surface, these tempests can be detected by changes in the strength of the Earth's magnetic field.

在地球表面，可以通过改变地球磁场强度来检测这些风暴。

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He also realised that varying the strength of an electric field would generate a changing magnetic field, even in empty space with no moving electric charges to speak of.

他同时认识到，变化电场强度将会产生一个变化的磁场，甚至在一个没有移动电子的空间中也是如此。

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It detects magnetic signals that are produced by the electrical activity of brain cells—and which have about a billionth of the strength of the Earth's magnetic field.

这种方法能探测到脑细胞电活动发出的磁信号——一种信号的强度只相当于地磁场的一万亿分之一。

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Moreover, there is (controversial) evidence of a long-term weakening trend in the magnetic field strength of sunspots.

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The most persuasive evidence that Voyager 1 has crossed the termination shock is its measurement of a sudden increase in the strength of the magnetic field carried by the solar wind, combined with an inferred decrease in its speed.

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Mr Wechlin adds that, during charging time, people stay inside the buses - something he says is absolutely safe, as the strength of the magnetic field produced is within the limits recommended by the International Commission on non-ionizing radiation protection (ICNIRP).

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