The Earth's radiation belts comprise electrons with energies from 0.01 to 10 MeV and protons with energies from 0.1 to 500 MeV trapped in the terrestrial magnetic field. The outer electron belt (L<3) is highly variable with space weather. During geomagnetic storms, the electron fluxes vary of several orders of magnitudes and the outer belt penetrates closer to the Earth. The plasmasphere is also eroded during geomagnetic storms so that the plasmapause goes closer to the Earth. In the present work, we describe the main characteristics and the correlation that exists between the dynamics of the radiation belts and that of the plasmasphere, as we obtained with SAC-C and CLUSTER observations.