Geocoronal Balmer-Alpha Emission Observed by the Wisconsin H-Alpha Mapper During the Southern Sky Survey

After a successful eleven-year run at Kitt Peak Observatory (AZ), the Wisconsin H-Alpha Mapper (WHAM) was moved to Cerro Tololo (Chile) in 2009 to complete the southern portion of the Galactic Balmer-alpha survey. Although WHAM is primarily used for making observations of the interstellar medium, the terrestrial emission present in each of WHAMs astronomical spectra offers a rich resource for studying the Earths atmosphere. Here we present an overview of the terrestrial Balmer-alpha emission collected during WHAMs first five years of operation under southern skies. Seasonal trends and comparisons with northern hemisphere observations will be discussed. WHAM can detect Balmer-alpha emission as faint as 0.05R in a 30s exposure, covering a 200 km/s (4.4 Angstrom) spectral region with 12 km/s spectral resolution from a 1 degree beam on the sky. With this sensitivity, hundreds of spectra can be collected in a single clear night. Although not capable of fully resolving the geocoronal Balmer-alpha line profile itself, WHAMs sensitivity makes it an exceptional instrument for geocoronal Balmer-alpha intensity observations.