As a meteorological expert with a focus on atmospheric electricity, I can provide a detailed explanation of the process that leads to lightning striking the ground.

Lightning is a massive discharge of electricity that occurs within a thunderstorm. It is a natural phenomenon that involves the transfer of electrical charge between the ground and a thundercloud, known as a cumulonimbus cloud. The process that leads to lightning is complex and involves several steps.

Initial Charge Separation
The first step in the formation of lightning is the separation of electrical charges within the thundercloud. This occurs due to the collision of ice particles, hail, and raindrops within the cloud. As these particles collide, they transfer electrical charge, leading to the formation of areas within the cloud that have different electrical charges. Typically, the upper part of the cloud becomes positively charged, while the lower part becomes negatively charged.

Development of Electric Field
Once the charge separation has occurred, an electric field develops between the negatively charged lower part of the cloud and the ground. The ground, being a good conductor of electricity, starts to accumulate positive charges in response to the negative charges in the cloud. This is due to the induction effect, where the presence of a charged object (the cloud) causes a redistribution of charges in a nearby conductor (the ground).

Atmospheric Breakdown
As the electric field between the cloud and the ground strengthens, the air, which is normally a good insulator, becomes ionized. This process is known as dielectric breakdown. The ionization creates a conductive path for the electrical discharge. This is a critical step because it allows the electrical charge to move from the cloud to the ground.

Stepped Leader and Streamer
The actual lightning discharge begins with a processional leader, which is a channel of ionized air that propagates from the negatively charged region of the cloud towards the ground in a series of steps. As the stepped leader moves downward, it emits a faint light and is followed by positive streamers that rise from the ground towards the leader. These streamers are attracted to the leader due to the strong electric field.

Connection and Return Stroke
Once a streamer from the ground connects with the stepped leader, a complete conductive path is established, and a massive flow of electrons from the cloud to the ground occurs. This is the return stroke, which is the bright flash of lightning that we see. The return stroke travels up the channel created by the stepped leader and can reach temperatures of around 30,000 Kelvin, which is five times hotter than the surface of the sun.

Repetition and Multiple Strokes
A single lightning flash can consist of multiple strokes as the leader and streamer process repeats. Each stroke can occur in a different location along the channel, and multiple strokes can happen in quick succession.

Factors Influencing Ground Attraction
Several factors can influence the attraction of lightning to the ground. These include the presence of tall objects, which can act as conductors and attract the lightning, and the local topography, which can affect the distribution of charges. Additionally, the moisture content and temperature of the air can influence the development of the electric field and the likelihood of a lightning strike.

In conclusion, lightning is attracted to the ground due to the development of a strong electric field between the negatively charged lower part of the thundercloud and the positively charged ground. This field leads to the ionization of the air, creating a conductive path for the lightning discharge. The process involves a series of steps, including the stepped leader, streamer connection, and return stroke, which together result in the powerful and visually striking phenomenon we know as lightning.

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A moving thunderstorm also gathers positively charged particles along the ground that travel with the storm. ... When the charge gets close to the ground, it is attracted by all the positively charged objects, and a channel develops. The subsequent electrical transfer in the channel is lightning.read more >>