Q-bursts — energetic ELF transients

Q-bursts are large-amplitude short transients in the ELF band that appear irregularly against the quasi-continuous background of the Schumann resonance. Whereas the background arises from the statistical sum of many lightning discharges from across the planet, a single Q-burst is excited by a single, particularly energetic discharge — typically a positive cloud-to-ground discharge. Ogawa 1967Guha 2017

Q-bursts were described by Ogawa et al. (1967) and gave their name to the entire class of phenomena. Their amplitude markedly exceeds the level of the background, so they appear in the record as sharp, isolated pulses. It is precisely this unambiguous link to a single source discharge that makes Q-bursts a valuable tool: unlike the background, which "blurs" the contributions of many storms, a Q-burst carries information about a single specific event and can be used to localize it and to study accompanying phenomena (see #66).

For the analysis of the modal parameters of the background, however, Q-bursts are disruptive: their large amplitude distorts the estimates of the frequencies and Q-factors. They are therefore removed from the time series by median filtering (a typical threshold on the order of ~16 CSD — see cluster E), so that large pulses do not distort the statistics of the background.