Radio quiet CME

The SOHO animation to the left shows a CME blasting off the sun. To the right is radio spectrum.

Radio bursts are classified as type I to type V and represent various circumstances of eruptions at the Sun. Both radio-quiet and radio-loud CMEs are associated with a type III burst (the vertical feature), which is due to electrons released from the Sun at the lift-off time of CMEs and are not due to CME-driven shocks.

There is no type II radio burst in the spectra in the right panel, something that is associated with radio loud CME.