A temporary decrease in the number of galactic cosmic rays reaching the Earth; also known as Forbush decrease. It occurs when an interplanetary disturbance, consisting of material ejected from the Sun (possibly a coronal mass ejection) and preceded by a shock front, travels outwards. As a result, there are increases in the strength of the interplanetary magnetic field and the density of the solar wind, which scatters incoming cosmic rays away from the Earth. The effect is named after the American geophysicist Scott Ellsworth Forbush (1904–84).
Subjects: Astronomy and Astrophysics.