Energetic neutral atoms (ENAs) consisting mainly of hydrogen with energies of several keV and coming from the outer heliosphere have been detected by various spacecraft missions. The characteristics of the energy spectrum of ENAs include a dependence on the proton distribution at the heliospheric boundaries where the solar wind interaction with the local interstellar medium (LISM) occurs. We determine here the time-dependent differential flux for the neutral hydrogen atoms resulting from the kinetic exchange of energy in the outer heliosphere under the solar magnetic field. With the proton flow along the magnetic field lines, the mean kinetic energy of the particles is shown to increases due to the magnetic field line compression at the outer heliosphere, causing the acceleration of the solar wind protons to the observed range of speeds. Also, the toroidal field driven compression and expansion of the magnetic field lines corresponds to the temperature variations observed in the INCA line-of-sight observations of the ENAs in the inner heliosheath, where as the pickup ions retain their accelerated speed inside the heliosphere in the subsequent motion up to ∼1au.