  We study the evolution of some microquasars during their outbursts as
observed with the X-ray telescopes RXTE and INTEGRAL. We focus on the interplay
between the accretion disc, and the medium responsible for the production of
the hard X-rays (the so-called corona). By comparing the behaviour of two
sources (XTE J1550-564 and GRS 1915+105) at X-ray energies and radio
wavelengths, we propose a scenario in which the discrete ejections are
triggered in coincidence with soft X-ray peaks during the outburst. We also
suggest, in those two sources, that the ejected material is the corona that is
seen to disappear in coincidence with the X-ray maxima. We then turn to two
other sources, XTE J1748-248, and XTE J1859+226, and study whether the same
conclusions can be drawn from the existing multi-wave length (radio+X-ray)
data.
