Neutrino flux asymmetry at  ~150, 300, 600 ms after bounce for model W15-3 as representative case. The 4π-maps show the relative variations ΔF/ ⟨ F ⟩  in the total (i.e., sum for ν and of all three neutrino flavors) neutrino energy flux in all directions. Hot spots (yellow and red) during the postbounce accretion phase (t ≲ 400 ms; top and middle panels) are connected to strong convective downflows in the neutrino-heated postshock layer. The typical scale of the corresponding high-emission areas is 20–30 degrees, and the amplitude of variations ranges around 10–30% during most of the time, though rare, single maxima can reach up to  ~70%. After the accretion has ended (t ~ 400–500 ms), the flux variation pattern is determined by the cell structure of the convection inside the proto-neutron star (i.e., below the neutrinosphere) and the variation amplitute decreases to a few percent (bottom panel). The number in the lower left corner of the plots (dℰ/dt) gives the total neutrino energy loss rate as flux integral over the whole emitting surface.