Inner magnetospheric proton distributions during storm development: an empirical 
approach applied to the 21-25 April 2001 storm

A. Milillo, S. Orsini, S. Massetti, A. Mura, N.Y. Ganushkina, P.C:son Brandt, 
E.C. Roelof


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
21-25 April 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 in order to
obtain the time-evolving model parameters. We compare the model parameters with the
geomagnetic indexes as well as with the solar wind data. We conclude that some
features of the proton spectra are recurrent during storms development, depending on
Solar Wind characteristics. By applying the model parameters to the Milillo et al.
[2001] empirical model with inclusion of the pitch angle distribution model by De
Benedetti et al. [2005], we can derive the global evolving proton distributions. The
total energy density development is analysed. In particular, this study evidenced how
the particles convected or injected from the night side during storm main phase
quickly decay and energize leaving a major role to the diffused particles. Finally
the ENA images are simulated and compared to the observed IMAGE/HENA images.

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European Geosciences Union General Assembly, Vienna, Austria, 2-7 April 2006