  We consider the non-radiative two body decay of a neutrino to a daughter
neutrino with degraded energy and a very light particle (Majoron). Ultrahigh
energy neutrinos from an astrophysical source like a Gamma Ray Burst undergoing
this decay process are found to produce different number of events in the
detector depending on whether they are Majorana or Dirac particles. The next
generation large scale experiments like Multi-OWL is expected to provide us an
accurate determination of the flux of neutrinos from astrophysical sources and
this may enable us to distinguish between the Dirac and Majorana nature of
neutrino.
