The Forbush decrease is usually observable by particle detectors on Earth within a few days after the CME, and the decrease takes place over the course of a few hours. Over the following several days, the solar cosmic ray intensity returns to normal. Forbush decreases have also been observed by humans on Mir and the International Space Station (ISS), and by instruments onboard Pioneer 10 and 11 and Voyager 1 and 2, even past the orbit of Neptune. The magnitude of a Forbush decrease depends on three factors: his size of the CME, the strength of the magnetic fields in the CME, the proximity of the CME to the Earth. These energetic particle effects can often be used to identify CMEs in the interplanetary medium, where they are usually called `Ejecta'. When both the Ejecta and shock effects are present the resulting cosmic ray event is called a `classical, two-step' Forbush decrease.