Thunderstorm electric fields

The Tata Institute, using GRAPES-3 claims to have measured the electric fields in a thunderstorm to be of order 1 gigaVolt.

Their detector measures mostly positively charged antimuons, and the electric field in a thunderstorm would tend to slow them down and reduce their energy--by of order 1GeV. This would cut down the rate considerably. High energy muons would make it without trouble, but fewer of the much more numerous lower energy ones would.

This is a clever measurement.

But.

I can't read the original paper yet, but Whitehorn pointed out that in a thunderstorm there's a gigantic updraft, so the density at high altitudes (10km and more) is a lot higher than before. That slows down muons too, and would likewise reduce the rates. I'm not sure how much.

Hariharan et al could well be right. There's a puzzle--we see anti-electrons from thunderstorms. That speaks of very large energies, which means very large accelerations, which means very large potential differences, and gigaVolt differences are about right.