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The high-velocity cloud (HVC) Complex A is a probe of the physical conditionsin the Galactic halo. The kinematics, morphology, distance, and metallicity ofComplex A indicate that it represents new material that is accreting onto theGalaxy. We present Wisconsin H-alpha Mapper (WHAM) kinematically resolvedobservations of Complex A over the velocity range of -250 to -50 km/s in thelocal standard of rest reference frame. These observations include the firstfull H-alpha intensity map of Complex A across (l, b) = (124, 18) to (171, 53)and deep targeted observations in H-alpha, [S II]6716, [N II]6584, and [OI]6300 towards regions with high H I column densities, background quasars, andstars. The H-alpha data imply that the masses of neutral and ionized materialin the cloud are similar, both being greater than a million solar masses. Wefind that the Bland-Hawthorn & Maloney (1999, 2001) model for the intensity ofthe ionizing radiation near the Milky Way is consistent with the known distanceof the high-latitude part of Complex A and an assumed cloud geometry that putsthe lower-latitude parts of the cloud at a distance of 7 to 8 kpc. Thiscompatibility implies a 5% ionizing photon escape fraction from the Galacticdisk. We also provide the nitrogen and sulfur upper abundance solutions for aseries of temperatures, metallicities, and cloud configurations for purelyphotoionized gas; these solutions are consistent with the sub-solar abundancesfound by previous studies, especially for temperatures above 10,000 K or forgas with a high fraction of singly-ionized nitrogen and sulfur.

Present-day Galactic Evolution: Low-metallicity, Warm, Ionized Gas Inflow Associated with High-Velocity Cloud Complex A