Lightning – AC or DC?

As we know that Lightning is an electric discharge in the form of a spark or flash originating in a charged cloud. Lightning is a very long electrical spark, ‘very long meaning greater than about 1 kilometer. Most lightning is generated in thunderstorms and is characterized by a length of 5 to 10 km, at the extreme about 100 km.

What appears as a single flash of lightning usually consist of a number of successive strokes, following the same track in space, at intervals of a few hundredths of a second. The average number of strokes in a multiple stroke is four, but may be as many as 40. The time interval between strokes ranges from 20 to 700 ms, but is most frequently 40-50 ms. The average duration of a complete flash being about 250 ms. Refer Understanding Lightning Phenomena for detail.

Thus we see that Lightningis a phenomenon which lasts for very few seconds and consists of many strokes of high magnitude. Therefore, Lightning is neither DC nor AC. It is more like an impulse signal or a series of occurrences of impulse signals.

A DC signal should have constant magnitude throughout the entire time. Mathematically its magnitude must be same in -∞<t<∞ .

Practically any signal whose ripple factor is less than three percent is taken as DC signal and its magnitude must be within the limits of ± 3 % during the usage period.

Thus Lightening cannot be a DC.

Lightning cannot be AC, since the wave shape of Lightning current is not sine-wave shaped voltage. A typical lightning current waveform looks something like this as shown below. This complete event (A, B and C) is a single strike.

Therefore, Lightning is neither DC nor AC. It is more like an impulse signal or a series of occurrences of impulse signals.

Thank you!

6 thoughts on “Lightning – AC or DC?”

  1. I was actually looking for info about lightning if it is AC or DC because I was planning to make my own design of DIY indoor lightning arrester.

  2. I could get intricate about the difference in AC and DC, but your reference to a lightning arrester is more or less how does a lightning arrester work? To begin with it’s best to keep in mind that there is a time prior to the flash of lightning during which there are molecules in the clouds and the earth that will interrelate with a charge, one with too many electrons and one with less. This keeps up until there is a high enough buildup to begin the spark called lightning. That is why AC/DC is irrelevant. What your DIY does is to setup a condition where the charge build up in the clouds will dissipate through the copper wire and buried copper rod and not through your home. Large radio and television antenna have those types of grounding rods to help keep their equipment and facilities near by free of the trouble associated with the charge buildup.


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