We review the construction of electron and proton wavefunctions in a uniform magnetic field. Keeping charged particles in cyclotron motions in mind, we adopt the symmetric gauge and its associated harmonic oscillator operator method. Furthermore, we apply this method to study the neutrino emission in the direct Urca process, e- + p → e + n, in very strong magnetic fields of the order of 1016 G, at a fixed temperature and appropriately chosen densities for relevant particle species to calculate the angular distributions of the neutrinos. We found some discriminative profiles of neutrino emissions peculiar to the Landau states in which the incoming particles reside. An implication on the asymmetry of the primordial neutrino emission in supernova phenomena is also discussed.