  Non-electromagnetic emission from cosmic ray particles accelerated in extreme
environments has been studied using different variations of semi-classical
formalisms. As the energy loss mechanisms of such particles is of great
interest, one must improve in some sense the previously intuitive description
of classical sources in the presence of fields. In this brief note we evaluate
the role played by the classical and dimensional proper acceleration of a
particle in radiation processes. One intends to show that the introduction of
the acceleration as a measure parameter gives an adequate scale for considering
the processes of massive particle emission. If the acceleration threshold is
not attained one is considering a regime where the processes of massive
particle production are suppressed. The analysis is performed in a
semiclassical formalism once applied in different contexts and already checked
for consistency in a serie of papers. As a further application of the results
we evaluate the possibility of a non negligible meson production by protons
accelerated in the framework of polar cap models operating in electromagnetic
fields of pulsars. It is shown that inside a systems endowed with magnetic
fields B\geq 10^{12} G the meson emission by protons must not be disregarded.
