  Two different model-independent mapping techniques have been applied to OSSE,
SMM, TGRS and balloon data and reveal a feature in the 0.511 MeV
electron-positron annihilation radiation pattern of our galaxy centered roughly
at l=-2 deg. and b=10 deg. with a flux of 5x10^(-4) 0.511 MeV ph/cm^2/s. If
near the galactic center, then positron sources are producing approximately
10^42 positrons/s which annihilate 1-2 kpc above the galactic plane. A
starburst episode within the inner few hundred pc of our galaxy would drive hot
pair-laden gas into the halo, with the one-sidedness pointing to the site of
initial pressure release at the onset of the starburst activity. Positrons lose
energy and annihilate as they are convected upward with the gas flow, and we
calculate high-latitude annihilation patterns and fluxes in accord with the
observations. Changes in the ionization state when the escaping gas cools could
give annihilation radiation substructure. The fountain of hot (10^6-10^7 K) gas
rising into the galactic halo would be seen through its enhanced dispersion
measure, thermal emission, and recombination radiation.
