Fig. 2From: Characteristics and longitudinal extent of VLF quasi-periodic emissions using multi-point ground-based observations1-h plot wave spectra on 21 December 2017. Example of 1-h plot wave spectra on 21 December 2017 from 19:00 to 20:00 UT showing a QP emission detected at two locations: a KAN and b IST. In this particular case, the QP emission shows one-to-one correspondence of elements as indicated by the black and white arrows, respectivelyBack to article page