  Spatial associations have been found between interstellar neutral hydrogen
(HI) emission morphology and small-scale structure observed by the Wilkinson
Microwave Anisotropy Probe (WMAP) in an area bounded by l = 60 & 180 deg, b =
30 & 70 deg, which was the primary target for this study. This area is marked
by the presence of highly disturbed local HI and a preponderance of
intermediate- and high-velocity gas. The HI distribution toward the brightest
peaks in the WMAP Internal Linear Combination (ILC) map for this area is
examined and by comparing with a second area on the sky it is demonstrated that
the associations do not appear to be the result of chance coincidence. Close
examination of several of the associations reveals important new properties of
diffuse interstellar neutral hydrogen structure. In the case of high-velocity
cloud MI, the HI and WMAP ILC morphologies are similar and an excess of soft
X-ray emission and H-alpha emission have been reported for this feature. It is
suggested that the small angular-scale, high frequency continuum emission
observed by WMAP may be produced at the surfaces of HI features interacting one
another, or at the interface between moving HI structures and regions of
enhanced plasma density in the surrounding interstellar medium. It is possible
that dust grains play a role in producing the emission. However, the primary
purpose of this report is to draw attention to these apparent associations
without offering an unambiguous explanation as to the relevant emission
mechanism(s).
