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AMS positron fraction 2013: explanation?<br />
• Dark matter decay? Beautiful candidate!<br />
• Nearby special source? Pulsars?<br />
• Cosmic ray physics? CR-positron fraction should show<br />
a gradual decay (Protheroe 1982)<br />
• Spallation along the way, so interaction and transport<br />
coupled? Spallation near source?<br />
• Consider magnetic field structure in wind of very massive<br />
stars, Maxwell laws in magnetic stellar wind; Parker<br />
(1958): Polar cap component at source E−2 : upturn of<br />
all CR spectra (1993: 2009+); interaction stronger in<br />
polar cap region, so more secondaries, so in spectrum<br />
secondaries shifted to lower energy, giving a E +1/3 prediction<br />
for positron fraction leveling off to a constant.<br />
4
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