Groups of narrowband IDBs (Events 45, 46, 47). Top panel: 11 June 2000, narrowband fibers with drift rate in the range −1.56 MHz s⁻¹ to −6.56 MHz s⁻¹ and total bandwidth, Δf_tot ≃ 4−19 MHz. Middle panel: 14 June 2005, typical fiber bursts overlapping with a cloud of mostly reverse-drift narrowband IDBs; their drift rate is ≃0.45−2.46 MHz s⁻¹, their total bandwidth (Δf_tot ≃ 1−6 MHz). Bottom panel: 21 April 2003, reverse drift narrowband fibers with emission component only. Their drift rate is 4.8 MHz s⁻¹ and the total bandwidth ≃5 MHz.