The radiation belts around the Earth were discovered by James Van Allen in the late 1950's using data from the earliest US satellites, and very quickly he concluded that the radiation levels were high enough to cause concern for human spaceflight. The belts have been well studied, but they're still not perfectly understood, for example the source of the low frequency radio waves that clear out the slot region between the inner and outer belts.

Using models of the belts and radiation analysis tools we show just how much radiation crew would be exposed to when flying through the belts and show that there are ways to reduce the exposure to safe levels.

The modelling of the exposure and dose levels uses ESA's Space ENVironment Information System
https://www.spenvis.oma.be/

Some clips created with Universe Sandbox
http://universesandbox.com/"