Two associated upward lightning flashes that produced opposite polarity electric field changes

Abstract

We have performed a study of two associated upward lightning flashes that involved two adjoining tall grounded objects with a time difference of about 45.8 ms. These two associated lightning are found to have opposite polarity, the first one being negative and the second one, positive. Their occurrence appears to be direct evidence that one upward lightning flash can trigger other upward lightning of opposite polarity from nearby tall grounded objects. Copyright 2009 by the American Geophysical Union.