Atmospheric Electricity
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Dalibard’s
Experiment
The Earth’s Electric Field
The “Carnegie”
Curve:
measurements
of the Earth’s
Electric Field
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Thunderstorm
Frequency
Charging Mechanisms
• Induction
– Result is a
polarized
hydrometeor
• Ion particle
charging
• Particle-particle
charging
E
-
---
+
++
+
+
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Charging by induction
Introduce a charge, creating an electric field
E
---
++
+
+
+
Initially neutral
Charging by induction
Contact 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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