In the heliosphere large fluctuations of the magnetic field are
sometimes observed,
especially at shocks (e.g. travelling interplanetary shocks, planetary
bow waves, and
shocks related to corotating interaction regions). The large fluctuations
very often
have an amplitude that reaches easily four or five times the magnitude
of the quiet
magnetic field. Since the plasma mostly contains a non-negligible fraction
of heavy
ions (e.g. helium ions or cometary water ions), these magnetic field fluctuations
are
described in terms of three-fluid equations. Here electrons, protons and
heavy ions
are considered as separate fluids interacting with themselves by electromagnetic
forces. The three-fluid equations are treated in such a way that we are
searching
for one-dimensional stationary waves. Thus the equations are reduced to
a fully
nonlinear set of ordinary differential equations, which have been evaluated
numerically
with respect to solitary waves. Subsequently, examples of solitary waves
in a
electron-
proton plasma loaded with 10 % 4He2+
ions are presented. For instance,
an enrichment of helium ions is observed within the solitary waves.