In the 1920s there were reports of something which came to be known as "Van Der Pol" waves (especially in Europe)Some people thought they were spirits as this mainly happened at night
What is the modern day expression used?

I have vaguely rememberance of it, but seems it had something to do with electricity....

Electrostatic sparks?

You are on the right track with electrostatic
Clue? The word I am seeking Is a sort of plant breeding term

Are you looking for "shock waves"?

quote:

Originally posted by Sailracer:
Are you looking for "shock waves"?

Never heard that in Plant breeding!
Its a word common to both of these
Giveaway clue; I suppose a greenhouse is a giant sized one?

One more chance..."Force Fields"?

Wave propagation? (Radio waves).

Thats the precise answer
Have to be a Physics Graduate to explain it
How you can hear distant stations after dark on AM and during High Sun spot activity (every 11 years)on Shortwave.