Positive Lightning is a type of lightning that, unlike common negative strikes, carries a positive charge from cloud to ground. Although they represent only 5-10% of all lightning, they are extremely dangerous as their energy is up to 10 times greater, their duration longer, and they often strike many kilometers from the storm (bolt from the blue). We analyze their formation mechanism, devastating effects, and why they pose the greatest challenge for lightning protection.
Positive Lightning: The Rare Bolts That Are 10 Times Stronger Than Normal
The "invisible killer" of storms: Energy, distance and the power of positive charge
When a storm approaches, most people seek shelter, aware of the danger of lightning. However, there is a type of lightning that is much rarer, more powerful and far more dangerous: Positive Lightning. These "mega-bolts" don't follow the usual rules, striking with terrifying force and often without warning, even in areas that appear to have clear skies.
1. The Physics of Charge: Negative vs. Positive
To understand positive lightning, we need to see how charge is distributed inside a storm cloud.
- Classic Lightning (Negative CG): In a typical storm, the bottom of the cloud carries negative electrical charge, while the ground below carries positive. The majority of lightning (90-95%) discharges this negative charge toward the positive ground. These are Negative Cloud-to-Ground (CG) lightning.
- Positive Lightning (Positive CG): In contrast, positive lightning transfers positive charge from the top of a storm cloud to the ground. This top portion of the cloud (the "anvil" of Cumulonimbus) often extends kilometers away from the storm core.
2. Why Are They So Dangerous?
- Enormous Energy: Positive lightning can carry currents of 300,000+ amperes (vs. 30,000 for negative) and energy up to 1 billion joules.
- Longer Duration: The discharge lasts longer, causing greater damage to struck objects.
- Greater Distance: They can strike 15-25 km from the storm, where skies seem clear.
- Single, Powerful Stroke: Unlike negative lightning with multiple strokes, positive lightning usually delivers one massive discharge.
3. The "Bolt from the Blue" Phenomenon
The term "bolt from the blue" describes positive lightning striking from seemingly clear skies. This happens because the bolt originates from the anvil cloud that has spread far from the storm center.
4. Protection Challenges
Standard lightning protection systems are designed for typical negative strikes. Positive lightning poses unique challenges due to its greater energy and unpredictable strike locations, requiring enhanced protection measures for critical infrastructure.
