What causes lightning and thunder?
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Causes of Lightning and Thunder
Lightning Formation: Electrical Discharge in Thunderstorms
Lightning is a powerful electrical discharge that occurs during thunderstorms. It is generated by the breakdown of electrical fields within thunderstorm systems, which can result in discharges that are cloud-to-cloud (CTC), cloud-to-air (CTA), or cloud-to-ground (CTG)6. The process begins with the separation of charges within the storm. The bottom of the thunderstorm typically carries a negative charge, while the top carries a positive charge. The ground below the storm also develops a positive charge4. This separation of charges is facilitated by the freezing of water to form ice crystals, which creates an electrical gradient due to the thermo-electric effect4.
Mechanism of Thunder: Rapid Air Expansion
Thunder is the sound produced by the rapid expansion and contraction of air surrounding a lightning bolt. When lightning strikes, it heats the air to extremely high temperatures, up to 30,000 K4. This sudden heating causes the air to expand rapidly, creating a shock wave that we hear as thunder4 6. The rapid expansion and subsequent contraction of the air generate sound waves, which travel through the atmosphere as thunder3.
Alternative Theories and Experimental Evidence
Historically, the cause of thunder has been a subject of scientific speculation. Early theories suggested that thunder was caused by the thermal expansion of the plasma in the lightning channel. However, experiments with short atmospheric arcs of lightning strength revealed that the plasma did not expand thermally in all directions but rather at right angles to the current, driven by electrodynamic forces1. This led to the hypothesis that thunder might be driven by the liberation of chemical bond energy from nitrogen (N₂) and oxygen (O₂) molecules, resulting in an air explosion2.
Environmental and Climatic Impact
Thunderstorms and lightning have significant environmental and climatic impacts. They can cause damage to infrastructure, disrupt aviation, and lead to loss of life and property3 8. Additionally, lightning produces nitrogen oxides (NOx), which are precursors to tropospheric ozone, a potent greenhouse gas8. The frequency and intensity of thunderstorms are influenced by surface temperatures, and with rising global temperatures, the occurrence of thunderstorms is expected to increase, particularly in regions like Africa3 8.
Conclusion
In summary, lightning is an electrical discharge caused by the separation of charges within a thunderstorm, while thunder is the sound produced by the rapid expansion and contraction of air heated by lightning. Although traditional theories focused on thermal expansion, recent evidence suggests that electrodynamic forces and chemical explosions of air may also play a role. Understanding these phenomena is crucial due to their significant environmental and climatic impacts.
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Most relevant research papers on this topic
The cause of thunder
Thunder is caused by a shockwave in air driven by the sudden thermal expansion of plasma in the lightning channel, with the Lorentz pinch force being too small and in the wrong direction to be the cause.
Evidence of thunder being a chemical explosion of air
Thunder is caused by an air explosion driven by chemical bond energy from nitrogen and oxygen molecules, rather than thermal expansion of the lightning channel.
The Mechanism of Thunderstorms and its Environmental Effects (A Review)
Thunderstorms cause significant damage to humans, infrastructures, and plants, and increasing surface temperature may increase their occurrence in Africa.
Literature ReviewThunder and Lightning
Thunder and lightning are created by lightning, with the separation of charges occurring due to the freezing of water into ice crystals.
A lightning climatology for Europe and the UK, 1990–99
Lightning is one of the most beautiful and terrifying, yet little understood, weather events on this planet. It is generated by the breakdown of electrical fields in thunderstorm systems, through discharges that can be cloud-to-cloud (CTC), cloud-to-air (CTA) or cloud-to-ground (CTG). The shock wave resulting from the rapid expansion of air heated in the discharge channel is heard as thunder. A comprehensive review of the processes involved is presented in the Royal Meteorological Society’s Scientific Statement on lightning (Royal Meteorological Society 1994). It is estimated that around the world every second there are more than 2000 active thunderstorms producing roughly 100 lightning flashes (Brookes Lightning are by
Physics: Thunder but no lightning
Thunderstorms can produce radiation without lightning, due to the close proximity of the radiation hemisphere to the ground.
Lightning Applications in Weather and Climate Research
Lightning can provide early warnings for severe weather, impact climate, and serve as a useful tool for tracking climate change in the future.
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