Positron production and annihilation in the Milky Way

SNIa in the Milky Way bulge may supply about 12% of the positrons required by observations of the 511 keV emission from the inner Galaxy, while positrons from disk SNIa may account for the totality of that emission. It is argued here that most of the disk positrons propagate away from the disk (due to the low density environment) and the resulting low surface brightness annihilation emission is currently undetectable by SPI/INTEGRAL. It is also argued that a large fraction of the disk positrons may be transported via the regular magnetic field of the Galaxy into the bulge and annihilate there. These ideas may alleviate current difficulties in interpreting INTEGRAL results in a “conventional” framework.