This lightning, a negative stepped leader, was filmed from an airplane.

这次闪电是一个负极梯级先导，它是从一架飞机上拍下的。

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Eventually a negative stepped leader travels downward and reaches the ground, creating a return stroke.

最终一个下行传播的负极梯形先导接触到地面，制造了一次回击。

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As the negative stepped leader gets closer to the tower, a positive leader forms from the tower tip and moves upward.

随着负极梯级先导向塔不断靠近，塔顶端的正极先导形成并且上行移动。

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Mr Duncan Smith had over-stepped his authority, blurring the lines between the party organisation and the leader's office.

ECONOMIST: Bagehot

At Merrill, board member Alberto Cribiore has stepped in as interim non-executive chairman and is leading the search for a new leader.

FORBES: Street Quakes As Another Chief Falls

The main rival to the 58-year-old Mr Bersani was Dario Franceschini, a former Christian Democrat who stepped in when the previous leader, Walter Veltroni, resigned in February after a disastrous showing in a regional election.

ECONOMIST: The Italian opposition gets a new leader��and a new scandal