On fast and slow Earth’s magnetospheric dynamics during geomagnetic storms: a stochastic Langevin approachTommaso Alberti, Giuseppe Consolini, Paola De Michelis, Monica Laurenza and Maria Federica MarcucciJ. Space Weather Space Clim., 8 (2018) A56DOI: https://doi.org/10.1051/swsc/2018039