Forbush decrease

The Forbush decrease is a reduction in received extreme energy cosmic rays for a period of time subsequent to a coronal mass ejection (CME) (i.e., fewer cosmic rays from beyond the solar system). The decrease begins after the CME, decreases over a few hours, remains low for a few days, and returns to normal. It is attributed to the magnetic field of the solar wind that is associated with the CME, presuming it diverts some of the solar systems' incoming cosmic rays.