  Ultrahigh energy neutrons and pions are likely to be produced in particle
interactions inside cosmic ray sources and subsequently decay to neutrinos and
other secondary particles ($\pi^\pm \rightarrow \mu^\pm\nu_\mu(\bar
\nu_\mu),\mu^\pm \rightarrow e^\pm \bar\nu_\mu(\nu_\mu) \nu_e(\bar\nu_e)$). In
high magnetic fields of the cosmic acceleration sites, the ultrahigh energy
charged particles may lose energy significantly due to synchrotron radiation
before decay. We show that for gamma ray bursts in the internal shock model the
flux of very high energy antineutrinos ($\bar \nu_e$) produced from decaying
ultrahigh energy neutrons can be more than the total neutrino flux produced in
pion decay depending on the values of their Lorentz factors, luminosities and
variability times.
