  We present in this proceeding some aspects of a model that should explain the
spectral state changes observed in microquasars. In this model, ejection is
assumed to take place only in the innermost disc region where a large scale
magnetic field is anchored. Then, in opposite to conventional ADAF models, the
accretion energy can be efficiently converted in ejection and not advected
inside the horizon. We propose that changes of the disc physical state (e.g.
transition from optically thick to optically thin states) can strongly modify
the magnetic accretion-ejection structure resulting in the spectral
variability. After a short description of our scenario, we give some details
concerning the dynamically self-consistent magnetized accretion-ejection model
used in our computation. We also present some preliminary results of spectral
energy distribution.
