What causes the outer Van Allen radiation belt to swell or diminish rapidly?

Answer

Solar activity and solar storms

The outer belt, extending from 13,000 to 60,000 kilometers, is highly sensitive to external space weather. When the Sun ejects plasma during solar storms, these particles interact directly with Earth's magnetic field. This interaction causes the outer belt to expand, contract, or change intensity by orders of magnitude within a few hours.

What causes the outer Van Allen radiation belt to swell or diminish rapidly?

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Discovery - Earth Has 3rd Radiation Belt | Video - YouTube

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