What is the relationship between solar activity variations and the measured Galactic Cosmic Ray (GCR) flux near Earth?

Answer

An inverse relationship, as the changing magnetic field deflects GCRs

The amount of Galactic Cosmic Ray (GCR) flux detected near Earth is not constant; it is modulated by the Sun's activity cycle. The mechanism linking these two is the heliosphere, the protective bubble created by the solar wind, which contains an interplanetary magnetic field configuration that changes over the solar cycle. This magnetic field acts as a shield, partially deflecting the incoming, highly energetic GCRs. Consequently, when solar activity is high, the heliosphere is more expanded or magnetically perturbed, leading to a decrease in the GCR flux reaching Earth. Conversely, during periods of lower solar activity, less shielding occurs, resulting in higher GCR arrival rates near Earth, establishing an inverse relationship between the two.

What is the relationship between solar activity variations and the measured Galactic Cosmic Ray (GCR) flux near Earth?

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