The innermost region of the Earth's outer core periodically flows faster or slower, and this action "tugs" at the planet's magnetic field, says Gillet.
地球外核最深区域呈阶段性快慢流动，这一行动“拽动”了地球磁场，吉莱说。
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In recent years, brain-imaging techniques, such as functional magnetic resonance imaging (fMRI) have allowed scientists to observe the brain in action and determine how groups of neurons function.