Inverted-polarity electrical structures in thunderstorms in the Severe Thunderstorm Electrification and Precipitation Study (STEPS) - Rust, W. David; MacGorman, Donald R.; Bruning, Eric C.; Weiss, Stephanie A.; Krehbiel, Paul R.; Thomas, Ronald J.; Rison, William; Hamlin, Timothy; Harlin, Jeremiah (Atmospheric Research, 2005)