  We propose a novel idea for the coherent intense millisecond radio emission
of cosmic fast radio bursts (FRBs), which have recently been identified with
flares from a magnetar. Motivated by the conventional paradigm of Type III
solar radio bursts, we will explore the emission of coherent plasma line
radiation at the electron plasma frequency and its harmonic as potential
candidates of the coherent FRB emissions associated with magnetar flares. We
discuss the emissions region parameters in relativistic strongly magnetized
plasmas consisting of electrons, positrons and protons. The goal is to make
observable predictions of this model to confront the multi-wavelength
observations of FRBs from magnetars. These results will impact both
observational radio astronomy and space-based astrophysics
