I do understand that lightning is caused by electrons flowing, between two electrically charged regions in the air or the ground, thus causing electrostatic discharge and equalization.
Though, on this site, there is no clear explanation on how these electrons flow, and if lightning is only possible in air or vacuum too, and whether it would be visible in vacuum.
There are basically two explanations:
Basically, lightning is visible because of the heat that is generated in the molecules of air, and the flow of the current is possible only because air atoms are ionized by the electric field, and the air molecules, in a plasma form, have atoms in excited state, and when these relax, they emit visible light. This is obviously not possible in vacuum.
Electrons, flowing as the lightning propagates, are free electrons, not bound to nuclei, and if they accelerate, they can emit visible light. Thus lightning would be possible in vacuum, and it could be visible too.
I have read these questions:
where G. Bergeron says:
The sort answer is no. Although the pulse of electric current will surely emit in the radio band as a normal antenna would via the process you're describing, emitting in the visible spectrum using the same process would require extreme acceleration of the electrons. This essentially the reason why you don't see visible light antennas. Most visible light is actually produced by electronic transitions in atoms or molecules. In the case of lightning, the current through the air is possible because the air is partly ionized by the electric field. This ionization is then maintained and maximized by the heat generated when the large current of a lightning bolt flows through the ionized channel. This heat is what produces most of the light. The heavily ionized air, now in a state of plasma, has many air molecules in an excited electronic state. When these excited states relax to their normal state, they emit light, much of it in the visible spectrum.
where aquirdturtle says:
Depends on what you mean by "lightning". Yes, because charge can flow across vacuum, but no, because you won't see anything. The visual effect that you see in the sky is actually a luminescent plasma that is left in the wake of the charge moving through the atmosphere. No atmosphere, no plasma, no light.
where AV23 says:
The conductivity of the vacuum is not a very trivial issue. In fact, depending on how you look at it, it behaves in two different ways. Firstly, there is no retarding force on any charged particle with constant velocity in vacuum. To this extent, no extra work is required in maintaining a constant current through any surface in vacuum. Thus, the resistance of the vacuum is in fact, infinite, as long as we define resistance in terms of the response of the charge carriers of a material. In this sense, we might say that it is an insulator - there are no charge carriers.
Since a "perfect vacuum" contains no charged particles, it normally behaves as a perfect insulator. However, metal electrode surfaces can cause a region of the vacuum to become conductive by injecting free electrons or ions through either field electron emission or thermionic emission.
So basically not only is the visibility of the lightning debatable, but the flow of the current itself in vacuum is contradictory too.
- Is lightning possible in vacuum and could it be visible?