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What is the Forbush effect on cosmic rays?

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The Forbush effect is a phenomenon in geophysics characterized by an occasional decrease in the intensity of cosmic rays observed on Earth.12

Discovered by physicist Scott E. Forbush in 1937, this effect describes an inverse correlation between cosmic ray intensity and solar activity. During periods of maximum solar activity, the Sun produces stronger magnetic fields that are carried into interplanetary space by the solar wind. These intensified magnetic fields act as a barrier, effectively blocking or modulating the flow of cosmic rays reaching Earth.12

This relationship is also observed over the 11-year solar cycle, where cosmic ray intensity is higher during solar minimums and lower during solar maximums due to the varying strength of these interplanetary magnetic fields.12