  We present the results of a spectroscopic monitoring program (from 1998 to
2002) of the H-alpha emission strength in HDE 226868, the optical counterpart
of the black hole binary, Cyg X-1. The H-alpha profiles consist of (1) a P
Cygni component associated with the wind of the supergiant, (2) emission
components that attain high velocity at the conjunctions and that probably form
in enhanced outflows both towards and away from the black hole, and (3) an
emission component that moves in anti-phase with the supergiant's motion. We
argue that the third component forms in accreted gas near the black hole, and
the radial velocity curve of the emission is consistent with a mass ratio of
M_X / M_opt = 0.36 +/- 0.05. We find that there is a general anti-correlation
between the H-alpha emission strength and X-ray flux in the sense that when the
H-alpha emission is strong (W_\lambda < -0.5 Angstroms) the X-ray flux is
weaker and the spectrum harder. On the other hand, there is no correlation
between H-alpha emission strength and X-ray flux when H-alpha is weak. During
the low/hard X-ray state, the strong wind is fast and the accretion rate is
relatively low, while in the high/soft state the weaker, highly ionized wind
attains only a moderate velocity and the accretion rate increases. We argue
that the X-ray transitions from the normal low/hard to the rare high/soft state
are triggered by episodes of decreased mass loss rate in the supergiant donor
star.
