Motion pictures have been taken at night by astronauts on the space shuttle showing lightning discharges that spread horizontally at speeds of 105 m·s−1 for distances over 60 km. Tape recordings have been made of the accompanying optical pulses detected with a photocell optical system. The observations show that lightning is often a mesoscale phenomenon that can convey large amounts of electric charge to earth from an extensive cloud system via a cloud-to-ground discharge.

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1 State University of New York at Albany, Albany, NY 12222

2 Atmospheric Sciences Division, Systems Dynamics Laboratory, NASA Marshall Space Flight Center, AL 35812

3 New Mexico Institute of Mining and Technology, Socorro, NM 87801