  The unexpected energy spectrum of the positron/electron ratio is interpreted
astrophysically, with a possible exception of the 100-300 GeV range. The data
indicate that this ratio, after a decline between $0.5-8$ GeV, rises steadily
with a trend towards saturation at 200-400GeV. These observations (except for
the trend) appear to be in conflict with the diffusive shock acceleration (DSA)
mechanism, operating in a \emph{single} supernova remnant (SNR) shock. We argue
that $e^{+}/e^{-}$ ratio can still be explained by the DSA if positrons are
accelerated in a \emph{subset} of SNR shocks which: (i) propagate in clumpy gas
media, and (ii) are modified by accelerated CR \emph{protons}. The protons
penetrate into the dense gas clumps upstream to produce positrons and,
\emph{charge the clumps positively}. The induced electric field expels
positrons into the upstream plasma where they are shock-accelerated. Since the
shock is modified, these positrons develop a harder spectrum than that of the
CR electrons accelerated in other SNRs. Mixing these populations explains the
increase in the $e^{+}/e^{-}$ ratio at $E>8$ GeV. It decreases at $E<8$ GeV
because of a subshock weakening which also results from the shock modification.
Contrary to the expelled positrons, most of the antiprotons, electrons, and
heavier nuclei, are left unaccelerated inside the clumps. Scenarios for the
100-300 GeV AMS-02 fraction exceeding the model prediction, including, but not
limited to, possible dark matter contribution, are also discussed.
