Lightning

Contents

• How lightning is formed?• Types of lightning• Lightning effects on objects• How to protect yourself?

Influence & Goal

• The unexplained mysteries of lightning.

• The aim – to explore the concept of lightning, its properties and safety methods.

Myths, religion and so on…

ZeusAncient Greece

PerkūnasBaltic

ThorNorse mythology

What now we know…

• Electrostatic discharge within two electrically charged regions of the cloud or between the cloud and ground.

Lightning activity

• The greatest concentration is in Central Africa, South-East Asia, the Himalayas and South America.

Types of lightning

Intra-cloud lightning

• The most frequent type of lightning.• It occurs between the lower and upper parts of cloud.

Cloud-to-cloud lightning

• Occurs between two clouds, from negatively to positively charged regions.

Cloud-to-ground lightning

Negative lightning

Charge distribution

• Positive ions goes to the top of the cloud while the basis becomes negatively charged.

• Small ice crystals goes up (updraft)

• Larger ones goes down (downdraft).

Polarization mechanism

• N.1 – electrical polarization of ice particles while moving in atmosphere’s electric field.

• N.2 – Electrostatic induction due to colliding ice particles.

Charging of the ground

• Two opposite charges repel each other, so the negative charge of the ground goes down.

Lightning formation

• A channel of ionized air (a “stepped leader”) travel from the negative and positive charged regions in their respective directions, until they connect.

The initiation of outward leaders

• Electric field is week by itself to initiate the process.• Relativistic electrons from cosmic rays are accelerated.

When they collide, the air is ionized.

Lightning formation

• Electrons flow from the top to the ground in little steps.

• It’s called a return stroke.

• Several strikes follows.

Thunder

• Excessive pressure, caused by extreme temperatures of the air, creates a thunder.

• Sound travels different distances to the observer.

Some numbers…

• 30 kA• 100 MV• 2.7 billion Watt-

hours

Kaunas

Positive lightning

• Originates at the top of the cloud and strikes the ground outside of the cloud shadow.

• “Blue from the top”

Positive lightning

• Makes up less than 5% of all lightning strikes.

• 10 times more powerful.

Lightning subtypes

• Ball lightning • Staccato lightning

Lightning subtypes

• Dry lightning • Superbolts

Sprites

• Noticed only in 20th century.

• Luminous plasma that occurs in high altitudes.

• Very fast.• Not well

explored.

Red sprites

Red sprites

Blue jets

Effect on objects

• Lightning vaporizes the fluid in objects.

• Forms fulgurites in sandy soil.

• Oxidizes nitrogen and creates nitrates.

Effect on objects

• Lightning emits electromagnetic impulses, which induces the current in wires and burn a device.

Effect on people

• 10 % dies.• People hit by lighting

suffer injuries of internal organs and damage to nervous system.

Effect on people

• Current flows a very short time.

• Some energy is radiated with heat and light.

• Most of the electric current flows around the object (“skin effect”).

Protection

• Hide inside the building or car.

• Avoid high ground and isolated trees.

Protection

• Isolate yourself from the ground.

• Don’t lie on the ground!

Power of nature

• Lightning takes nearly 500 lives each year, and leaves 5000 with severe injuries.

• The odds to be struck by lightning are 1/12000.

Human Lightning Rod

• Got hit by lightning 7 times and lived.

• Was named Human Lightning Conductor

• Recognized by Guinness World Records

Roy Cleveland Sullivan1912-1983

Conclusion

• Lightning is a sudden electrostatic discharge within the oppositely charged regions of the cloud or between the clouds and ground.

• Return stroke (a flash) occurs when two stepped leaders connect and electrons start flow from the cloud to earth step by step.

• There are diversity of lightning types.• Lightning is a powerful natural phenomenon

and one, to be cautious of.

Thanks for listening