Petra - I'd suggest re-reading Lowell's article - I've posted a link in response to Roger's query a few messages down -

At the very least you might want to read the CONCLUSIONS area of this post:
http://www.earthwaves.org/wwwboard/messages/13175.html

About the only thing I don't see mentionsed is Electron Flux. (Or I missed it)

Canie

• Review paper on Electrical/EQ Lights/ etc. - Part 3