LAUSR

Bow-shock pulsar wind nebulae (PWNe) show a variety of morphological shapes. We attribute these variations to the intrinsic properties (relative orientation of the pulsar's spin, velocity, and magnetic inclination angle) - as well as the line of sight. We identify three basic types of bow-shock nebulae: (i) a "rifle bullet" (spin and velocity aligned); (ii) a "frisbee" (spin and velocity orthogonal, spin is in the plane of the sky) and (iii) a "cart-wheel" (like frisbee but the spin is perpendicular to the plane of the sky). Using 3D relativistic MHD simulations, as well as analytical calculations, we reproduce both the key morphological features of the bowshock PNEs, as well as variations are seen in different systems. Magnetic stresses within the pulsar wind strongly affect the overall structure, producing "whiskers", "tails", "filled-in" and "mushroom" shapes, non-symmetric shapes etc. On the other hand, the ISM inhomogeneities, as well as the anisotropy of the wind luminosity, produce only mild variations of the PWN shape. In few cases we clearly identify the morphological structure - our results do not favor alignment of the pulsar spin and linear velocity. Our calculations of the underlying radiative process explain low synchrotron $X$-ray efficiency (in terms of the spin-down luminosity) and argue for energetically subdominant contribution of the IC processes.