Like闪电，圣埃尔莫的大火是等离子体, or ionized air that emits a glow. But while lightening is the movement of电从充电cloudto the ground, St. Elmo's Fire is simply sparking, something like a shot of electrons into the air. It's a电晕放电, and it occurs when there is a significant imbalance in electrical charge, causing molecules to tear apart, sometimes resulting in a slight hissing sound.
The first step in generating St. Elmo's Fire is a thunderstorm. As you can learn inHow Lightning Works, a thunderstorm creates an electrically charged atmosphere. There is a charge difference between the storm clouds and the ground, and this difference creates voltage, or electrical pressure. In between the clouds and the ground, theatomsin the air undergo changes; most important to our discussion, electrons move farther away from protons, creating an environment that allows electrons to move around freely. In other words, the air becomes a good conductor.
Once the air is conducive to the movement of electrons, those electrons continue to increase the distance between their positively charged counterpart, protons. This isionization，血浆简直就是电离空气。引起圣埃尔莫（St.作为潜在的避雷针。
当电压变得足够高时，通常大约30,000伏的空间，带电的物体将排放其电能[来源：科学美国人]。圣埃尔莫（St.尖顶，桅杆或飞机翼的尖端显示出凝结的表面电荷。
When the air molecules tear apart, they emit light. In the case of St. Elmo's Fire, the discharge is continuous -- sometimes lasting several minutes -- and creates a constant glow. The glow is blue because different gasses glow different colors when they become plasmas.Earth's大气中有氮和氧气，这种特殊的组合恰好是发光蓝色。
圣埃尔莫（St. Elmo）的大火正是霓虹灯管中发生的事情 - 本质上是连续的火花。如果地球的大气是由霓虹灯组成的，那么圣埃尔莫的火就会发光橙色而不是蓝色。霓虹灯管仅是玻璃中包含的圣埃尔莫大火。圣埃尔莫（St. Elmo）的火还表现得像等离子地球仪。一位飞行员描述了在飞行风暴云时，她的小飞机挡风玻璃上发生的现象。当她触摸挡风玻璃内部时，蓝色条纹伸向手指的尖端[来源：今日美国]。
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