spectrum, therefore, samples only the local dark matter distribution and is thus subject to considerably less uncertainty than the other anti-matter species. Additionally, data from the HEAT [@heat] and AMS-01 experiments [@ams01] contain features which could plausibly be the consequence of dark matter annihilations in the local halo.

The spectral shape of the cosmic positron spectrum generated in dark matter annihilation depends on the leading annihilation modes of the WIMP in the low velocity limit. Bino-like neutralinos, for example, typically annihilate to heavy fermion pairs: $b\bar{b}$ with a small $\tau^+ \tau^-$ admixture, along with a fraction to $t\bar{t}$ if $m_{\chi} \gsim m_t$. Wino or higgsino-like neutralinos annihilate most efficiently to combinations of Higgs and gauge bosons. In other particle dark matter candidates, such as Kaluza-Klein dark matter in models with universal extra dimensions, annihilation to light charged leptons can lead to a much harder positron spectrum than is expected from neutralinos [@kkpos].

Once positrons are injected into the local halo through dark matter annihilations, they propagate under the influence of galactic magnetic fields, gradually losing energy through synchrotron emission and inverse Compton scattering with radiation fields, such as starlight and the cosmic microwave background. The spectrum observed at Earth is 