Comparison Between Radio Loud and Radio Quiet Fast CMEs: A Reason for Radio Quietness

It is well known that fast CMEs are mostly associated with magnetohydrodynamic (MHD) shocks in the solar corona, forming type-II radio bursts. However, absence of bursts not uncommon. Herein, we aim to analyze differences between loud (RL) and quiet (RQ) Coronal Mass Ejections (CMEs) (speed ≥ 900 km s−1) during Solar Cycle 24 (2008 – 2021). From 309 CMEs, could identify 143 events a source origin on visible disk (Earth view). We identified flares/CMEs for using running-difference images from (i) Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA) (ii) Large Angle Spectrometric Coronagraph (LASCO) observations. Among these events, RQ RL groups have 70 73 respectively. CALLISTO Wind/WAVES observations used sets. analyzed possibilities streamer-CME CME-CME interaction. In this study, report important underlying reasons quietness CMEs. LASCO field view, majority (almost 90%) interacted streamers and/or pre-CMEs, whereas only 25% did same, there was no pre-CME The observational evidence led conclusion substantial density perturbation/interaction increases probability production emissions by shock