Which term describes the initial path of ionized air that travels toward the ground to start a lightning discharge?

• A. Thunder
• B. Stepped leader
• C. Ground spark
• D. Humidity rise

Answer: (B)

The initial downward path of ionized air that starts a lightning discharge is called a stepped leader. It forms when the strong electric field between the cloud and the ground ionizes air, creating a conductive channel. Rather than a single smooth stroke, this channel advances in short, rapid steps, reaching downward in a ladder-like progression and often branching as it searches for a path to ground. When the downward leader nears the ground, an upward discharge from the ground can connect with it, and a rapid return stroke travels up the channel to produce the bright flash. Thunder is the sound produced by the rapid heating of air along the channel, not the initiating path itself. The other terms don’t describe this downward, stepping process.