Spider lightning refers to a specific type of lightning discharge characterized by its unique appearance and location. It's not your typical bolt from the sky, but rather a fascinating horizontal display.
Understanding Spider Lightning
Here's a breakdown of what makes spider lightning unique:
- Horizontal Travel: Unlike most lightning that streaks vertically, spider lightning flashes travel horizontally, often extending long distances across the sky. This is a key identifier.
- Location: Spider lightning is typically observed on the underside of stratiform clouds. Stratiform clouds are those large, sheet-like clouds that often cover the sky.
- Association with +CG Flashes: Spider lightning is frequently linked to positive cloud-to-ground (+CG) flashes. These types of flashes involve a transfer of positive charge from the cloud to the ground.
Key Differences from Regular Lightning
| Feature | Regular Lightning (CG) | Spider Lightning |
|---|---|---|
| Direction | Primarily Vertical | Primarily Horizontal |
| Location | Anywhere | Underside of stratiform clouds |
| Association | Negative charge transfer most common, also positive | Often linked to +CG flashes |
| Appearance | Typical, well defined bolt | More extensive and horizontal |
Why Is it Called Spider Lightning?
The name "spider lightning" comes from its web-like appearance. Its branching, horizontally travelling paths often make it look like a spiderweb spread across the cloud base.
How Does Spider Lightning Form?
Spider lightning occurs within clouds as a result of the complex charge dynamics within thunderstorms.
- Charge Separation: Storms develop strong electrical fields, with different regions accumulating different electrical charges.
- Horizontal Discharge: The discharge travels through channels within the cloud, extending horizontally due to factors like charge distribution and air density differences.
- Visibility: This discharge is made visible as light when electrons are excited and release photons.
Summary:
In summary, spider lightning is a unique and visually striking form of electrical discharge characterized by its horizontal paths along the underside of stratiform clouds. It is often connected to positive cloud-to-ground flashes and gets its name from its branching, web-like appearance.
