Atmospheric Electricity
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Dalibard’s Experiment
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The Earth’s Electric Field
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The “Carnegie” Curve: measurements of the Earth’s Electric Field
Thunderstorm Frequency
Charging Mechanisms
• Induction– Result is a
polarized hydrometeor
• Ion particle charging
• Particle-particle charging
E+++
++
--- -
-
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Charging by induction
Initially neutral
Introduce a charge, creating an electric field
+-----
+
++
+ + E
Charging by inductionContact charging
- +
E
Selective Ion Capture
- - - - --
--
--
+ + + ++
++
+ ++
- +
E
Gravity plays a role in differential charge separation
Negative charge transfer to larger particles, which then fall to lower levels in the cloud.
The Earth’s Electric Field
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Storm Electrification
• Is NOT well understood• There is more than one
parameter– Buoyancy– Hydrometeor type– Conductivity
• Even within the same storm
• Role of charge separation
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Corona or Point Discharge
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• The presence of some sort of conductive point• Disruption of the
Electric Field• Electron Avalanche
(non-ohmic)
Corona (point discharge)
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Lightning Types
Frequency of occurrence
The Electrification of thunderstorms is related to thermodynamics
Different slopes for different storms
Why the slopes may differ
Flash rate is greatest when storm intensity is greatest
Cloud Physics and electrification
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Hail and ground strokes
Field Mill
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