  Recent X-ray observations in the central compact remnant of Puppis A and
other young pulsars have provided convincing evidence about the anti-magnetar
nature of the so-called central compact objects (CCOs). The measured period
derivative, corrected by the proper movement, provides exceptionally low
superficial magnetic fields for such sources. Using the dipole radiation
canonical model, the superficial magnetic field of the CCO (RX J0822-4300) in
Puppis A was estimated to be $B\simeq 2.9 \times 10^{10}$ G. In this paper, we
present a numerical model to interpret the unusual magnetic-field behavior in
RX J0822-4300. Using the magnetohydrodynamic simulations during the
hypercritical accretion phase, we propose that a variety of MeV neutrinos is
created given evidence about the submergence of the magnetic field in the
pulsar. We investigate the production, propagation, oscillations, and detection
of MeV neutrinos from this source. The detection of neutrino events with their
flavor ratios would be a compelling signature of the decreasing evolution of
the magnetic field not only in RX J0822-4300 but also in CCO candidates.
