If Blitztrichter is meant in this context:
"Es entsteht am Einschlagsort ein sogenannter Blitztrichter der sich wellenmäßig ausbreitet,ähnlich einem Stein der ins Wasser geworfen wird.Heißt also, daß die vom Einschlagsort ausgehenden hohen Spannungen und Ströme sich wellenartig ausbreiten,und somit auch noch in 1-2 Kilometer Entfernung erheblichen Schaden an elektronischen Geräten wie TV,Rechnern usw. anrichten können.",

then I would suggest "ground current" or "radial ground current".

This is form the second link "clearing up" lightning myths
"When lightning hits the ground nearby, it is 'grounded ' and I am safe."

"Totally and absolutely FALSE. Despite the fact that we call the earth a "ground," it is very difficult to pump electricity into the ground. Most "earth" is a very good insulator. When lightning hits the ground, it spreads out along the surface and first few inches of the ground in increasing circles of energy called "ground current." If it contacts a fence or a water pipe or wire entering a house it can be transmitted for quite a distance and cause injury to persons near these paths. People, being bags of electrolytes, are better transmitters of electrical current than most ground is, and many are injured by ground current effect each year as the lightning energy surges up one leg that is closer to the strike and down the one further away."


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Note added at 53 mins (2014-03-26 11:52:32 GMT)
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This citation also uses radial ground current:
"When lightning strikes the ground radial currents spread out from the site of the strike causing damage to anything nearby."

http://www.aharfield.co.uk/lightning-protection-services/abo...