Sprites triggered by negative lightning discharges

High altitude air breakdown, manifested as “red sprites,” is reported in close association with negative cloud‐to‐ground lightning (−CG) on at least two occasions above an unusual storm on August 29, 1998. Data from high speed photometry, low‐light‐level video, and receivers of lightning electromagnetic signatures in the frequency range 10 Hz to 20 kHz are used to establish the association and indicate that the causative −CG discharges effected unusually large vertical charge moment changes (ΔM Qv ) of up to 1550 C · km in 5 ms. The existence of sprites caused by −CG's, rather than the regularly associated +CG's, has immediate implications for sprite models and observations.