In a nutshell, an area of positive charge develops in the upper reaches of the cloud, while the lower and middle parts of the cloud take on a negative charge as positive charge develops on the ground. Let's first look at the typical distribution of electrical charges in a typical thunderstorm (see image below). Why is that? Well, for lightning to occur, we need an electric field that results from electrically charged particles, and air rising rapidly thanks to positive buoyancy within cumulonimbus clouds can create a separation of charges as large as several hundred million volts (a million times greater than the voltage in a typical home). So, you can't have a thunderstorm without lightning.Īnd, if you can't have a thunderstorm without lightning, you can't have a thunderstorm without speedy, convective updrafts. Farther away, shock waves give way to sound waves, and peals of thunder reverberate for several miles. Moreover, super-heated air expands rapidly, producing shock waves that are heard as sharp claps or bangs near the strike. That's hotter than the surface of the sun! Such intense heating prompts the emission of visible light. As a result of air's high resistance, lightning rapidly heats a narrow channel to temperatures near 50,000 degrees Fahrenheit (resistors warm when electricity passes through them). Lightning is simply an electrical discharge from a cumulonimbus cloud that occurs when an imbalance in electric charge exceeds the electrical resistance of the air (the electrical resistance is substantial because air near sea level has a low electrical conductivity).
In the most basic sense, lightning is like a spark from a light switch to your finger after you walked across a carpet during the wintertime.
#Heat lightning series
If you want to read more about the "parts" that make up a lightning strike (namely "stepped leaders," "return strokes," and "dart leaders") check out this series of pages on the anatomy of lightning from the National Weather Service.Ĭomplexities aside, lightning is the difference between a convective rain shower and a thunderstorm. Here's another slow-motion video of a lightning strike (credit: NOAA) which confirms that there seem to be multiple "parts" to a lightning strike (here's the same video slowed down even more). A lightning bolt is not a single "flash in the pan." Lightning is actually quite complex, as the spectacular slow-motion lightning video on the right shows. Regardless of the type of lightning, there's much more to lightning than meets the eye. I'd imagine that people started using the term "heat lightning" because they noticed lightning without thunder on very warm, humid summer nights as thunderstorms roamed in the distance. What most people refer to as "heat lightning" is just lightning that's created in a distant thunderstorm (too far away to hear the thunder). That's because there's no such thing as "heat lightning" (as in, lightning caused by heat). By the way, you may have noticed that I didn't mention "heat lightning" as a type of lightning. Other, much less common forms of lightning also exist, such as cloud-to-air lightning, and sprites. Intra-cloud (IC) and cloud-to-cloud (CC) lightning are much more common and account for two-thirds to three-fourths of all lightning flashes. You might think of lightning as a "bolt" from a cloud to the ground, but such "cloud-to-ground" (CG) lightning only accounts for about a fourth to a third of all lightning. Research suggests that more men may be struck by lightning because they're more likely to be in vulnerable outdoor situations where finding shelter may be difficult (boating, fishing, camping, doing construction work, etc.), and they're too slow (or reluctant) to be convinced of the imminent threat of lightning. Of those killed each year by lightning, on average, nearly 80 percent are male. Despite the decrease in lightning fatalities (even while a large increase in population occurred), each year in the United States a few hundred people are struck by lightning and a few dozen die (on average), so there's still work to be done.
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