Kraftt & Savoini (2022) studied the effect of density fluctuations on coherent emission induced by the interaction of plasmas with a weak beam of energetic electrons, using particle-in-cell (PIC) simulations. The purpose is to figure out the generation mechanism of plasma emissions at higher (the thrid and the fourth)  harmonics. With careful evaluation we have identified serious problems of their physical deductions and data processing methods. Here we report such critical comments and present results of our PIC simulations of the same issue.
 

Plasma astrophysics (1261); Solar electromagnetic emission(1490); Solar radio emission(1522); 20 Radio bursts (1339); Space plasmas(1544);