These burst from December 12th 2013 look like this is the effect of ionospheric gravity waves. This spectral features are known as caustics or caustic spikes, and they are due to the ionosphere (traveling ionospheric disturbances TIDs). The effect is local, that's why we observe different features at different locations. These effects (to my knowledge) were only observed in European region (Birr/Ireland, Essen/Germany, Glasgow/UK and Nançay/France.
