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Galactic spiral shocks are dominant morphological features and believed to beresponsible for substructure formation within spiral arms in disk galaxies.They can also contribute a substantial amount of kinetic energy to theinterstellar gas by tapping the (differential) rotational motion. We usenumerical hydrodynamic simulations to investigate dynamics and structure ofspiral shocks with thermal instability in vertically stratified galactic disks,focusing on environmental conditions (of heating and the galactic potential)similar to the Solar neighborhood. We initially consider an isothermal disk invertical hydrostatic equilibrium and let it evolve subject to interstellarcooling and heating as well as a stellar spiral potential. Due to thermalinstability, a disk with surface density $\Sigma_0 \geq 6.7\Surf$ rapidly turnsto a thin dense slab near the midplane sandwiched between layers of rarefiedgas. The imposed spiral potential leads to a vertically curved shock thatexhibits strong flapping motions in the plane perpendicular to the arm. Theoverall flow structure at saturation is comprised of arm, postshock expansionzone, and interarm regions that occupy typically 10\%, 20\%, and 70\% of thearm-to-arm distance, in which the gas resides for 15\%, 30\%, and 55\% of thearm-to-arm crossing time, respectively. The flows are characterized bytransitions from rarefied to dense phases at the shock and from dense torarefied phases in the postshock expansion zone, although gas with too-largepostshock-density does not undergo this return phase transition, insteadforming dense condensations. If self-gravity is omitted, the shock flappingdrives random motions in the gas, but only up to $\sim 2-3 \kms$ in thein-plane direction and less than $2\kms$ in the vertical direction.Time-averaged shock profiles show... (abridged).

Galactic Spiral Shocks with Thermal Instability in Vertically Stratified Galactic Disks