THE STRIKE

Storm clouds are electrically charged much like a great big electrical capacitor in the sky. The top portion of the storm system is positively charged, and the bottom section is negatively charged. How this is accomplished is still a topic of debate, but the widely agreed upon theory explains that within the storm clouds, the moisture that makes up the cloud collides with other water droplets and moisture. These collisions cause ions to separate or get “knocked off” from their rising moisture hosts, thus creating a charge separation.

These knocked off electrons gather at the bottom portion of the cloud creating a large negative charge. The rising moisture that had the electrons stripped continues to rise to the upper section of the cloud system, thus creating a large positive charge at the top.

On the earth’s surface, the attracting forces of the negative charge at the base of the cloud causes a positive charge to form on the earth’s surface, thus creating an electric field. All that is now needed is a conducting path for the charges to come together and even themselves out.

At this point, the electric field becomes so strong that the air molecules begin to break down. This means that the air molecules begin to separate into positive and negative electrons. This in-turn gives the ionized air to move more freely, creating plasma. This plasma is more conductive giving the electric fields the needed conductive path to even their charge separation out. The plasmas are created by both the clouds, traveling down, and by the earth’s surface, traveling up.

There are many variables in the formation of these plasmas. Dust or any other objects or impurities may cause plasmas to generate in any direction. Also, the electric field may vary for the surfaces, both the clouds and earth. Some objects are more susceptible to lightning strikes due to the fact that they create a bigger electric field, however, this does not guarantee what path the lightning will take.

courtesy: Mark McEuen @ www.owlnet.rice.edu

The actual visual effect that we see is not the electrical current flowing from point A to B, but the effect that the current has on the surrounding air molecules. The heat generated by the current flow is so intense that it actually “explodes” the surrounding air molecules. This explosion is the vision effect, and the sound effect. “Thunder” is the effect of the air exploding and the ensuing shockwave.

(How Stuff Works: Lightning Strikes)

 

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