由于太阳活动日趋频繁，在中纬度地区南北纬40度或以上地区也有可能出现绚丽多彩的极光现象。

With the increasing level of solar activities , it will likely trigger dazzling auroral displays at mid - latitudes 40 or above degrees north south from the equator.

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上地幔一个最显著的现象就是低速带，就像这个词名所表达的那样，在上地幔存在这么一个区域，在那里地震波波速会发生减慢。

The most remarkable feature of the upper mantle is the low-velocity zone. as suggested by its name, this is a region in the upper mantle in which there is a decrease in the speed of seismic wave.

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