China's space probe uncovers new solar effect on cosmic rays

Solar activity has a significant impact on the interplanetary space environment.

Plasma clouds ejected during coronal mass ejections (CMEs), along with the magnetic fields they carry, can substantially alter the magnetic environment of interplanetary space, thereby affecting the propagation of cosmic rays. One of the primary effects observed on Earth is a decrease in cosmic ray flux lasting from several days to a few weeks, followed by a gradual recovery to normal levels, a phenomenon known as a "Forbush decrease." Precise observation of this effect serves as an important probe for understanding changes in the interplanetary environment.

Recently, the international collaboration team of the Dark Matter Particle Explorer satellite, "Wukong," utilized eight years of observational data to precisely measure eight Forbush decrease events involving electrons and positrons. For the first time, the study revealed the behavioral characteristics of electron and positron fluxes during both the decline and recovery phases as well as their correlation with the physical parameters of CMEs responsible for the Forbush decreases. The findings were recently published in the international academic journal Physical Review Letters.

"Wukong," China's first spaceborne dark matter particle detection satellite, was launched in December 2015 and entered its orbit. The satellite boasts high energy resolution and strong particle identification capabilities, offering distinct advantages in the spatial observation of electrons and positrons. By analyzing data collected by "Wukong" from 2016 to 2024, the research team identified eight electron and positron Forbush decrease events and precisely measured the flux variations during these events. This research holds significant implications for advancing the study of cosmic ray propagation and changes in the solar-terrestrial space environment.