Storm-time Global Evolution of the Inner Magnetospheric Proton Distributions: an Empirical Approach Applied to the April 21-24th 2001 Storm A. Milillo, S. Orsini, A. Mura, M.W. Liemohn, and P.C. Brandt The empirical approach in global modelling the proton distributions of the inner magnetosphere [Orsini et al., 2004] is here applied for a detailed analysis of the April 21-24th 2001 storm. This method based on comparison of the Milillo et al. [2001] model with local proton spectra, results as a simple and powerful tool for inner magnetospheric studies. In this work we use the LANL proton spectra and other available data in order to obtain the time evolving model parameters. By applying these parameters to the Milillo et al. [2001] empirical model we can derive the global evolving proton distributions. The macroscopic physical features and their developments on a global scale are analysed in terms of magnetic pressure, electric potential, equatorial current and total energy. Then, we compare both the model parameters and the derived quantities (related to the ring current) with the geomagnetic indexes as well as with the solar wind data. Finally, the presented results are discussed in the light of energetic neutral atom data from IMAGE. _______________ Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004