  The dynamics of a galactic disk in a non-axisymmetric (triaxial) dark halo is
studied in detail using high-resolution, numerical, hydrodynamical models. A
long-lived, two-armed spiral pattern is generated for a wide range of
parameters. The spiral structure is global, and the number of turns can be two
or three, depending on the model parameters. The morphology and kinematics of
the spiral pattern are studied as functions of the halo and disk parameters.
The spiral structure rotates slowly, and its angular velocity varies
quasi-periodically. Models with differing relative halo masses, halo semi-axis
ratios, distributions of matter in the disk, Mach numbers in the gaseous
component, and angular rotational velocities of their halos are considered.
