Institute of Astronomy
Radio Astronomy and Plasma Physics Group
Eidgenössische Technische Hochschule Zürich
Swiss Federal Institute of Technology,  Zürich
          
Conclusions
The emission physics is generally still unclear for coherent radio bursts in the decimeter range.
Even type III bursts are quantitatively not understood:
  - very high frequency emissions
  - even before flare
  - not related to electron acceleration rate
Narrowband spikes and pulsations are not understood even qualitatively
The plausible causes are a small number (electron beams, flare waves, trapped electrons and a few more).