St. Elmo's Fire not dangerous?

Question

I know that St. Elmo's Fire is a form of plasma that occurs during thunderstorms that is similar to lightning because it is formed by a difference in charges. But why isn't it dangerous if St. Elmo's Fire is around you? For one, the fact that there is a charge difference usually means an electric shock, whether that is a tiny bit of static electricity from touching metal or a lightning strike. Yet St. Elmo's Fire is caused by a charge difference but doesn't give you an electric shock. Also if there is a charge difference around you, lightning is more likely to strike you, even if you are as low as you can be. This can lead to heart problems such as tachycardia, fibrillation, or asystole. It can also cause uncontrollable muscle movements which itself can be dangerous because if your muscles are out of control you can end up anywhere. Muscles being out of control can also mean things like vomiting, lots of mechanical digestion, high blood pressure and more from involuntary muscles being out of control. In any case it is dangerous to have voluntary or involuntary muscles out of control. It can also cause nervous system problems, in particular excitation toxicity from positive charges continously reaching neurons until they don't send a signal. So with all the health problems that can result and the difference in charges itself without an electric shock, why is St. Elmo's Fire not dangerous?

Answer 1

Hi Asked,

Well that's a pretty large statement to respond to. But passage of electric current through a living creature is harmful in proportion to the (1) energy dissipated, and (2) voltage spike locally generated in tissue.

So, simply charging a creature up to a high voltage is innocuous, b/c no current is passing, hence no energy is being dissipated, and any voltage changes are gradual. That's the situation with St. Elmo's Fire; there's no path for charge to a ground.

But, provide a path to a ground suddenly, and then you get a shock.

Your body can generally tolerate the sudden discharge of several thousand volts of static electricity to a ground, as when you spark to a grounded metal shelf after shuffling across the carpet with shoes on. But if a hundred people in a connected line had shuffled, and the last one touches the shelf -- oops!

-- Cheers, -- Mr. d.