Fig. 1From: Polarization measurements of unusual cases of medium frequency burst emissions extending below 1.5 MHzSpectrograms showing six examples of MFB emissions observed at five sites. The events are all of an unusual type, in which the MFB has a distinct lower cutoff at 1.3–1.5 MHz, with a gap below, and sporadic emissions extending from below the gap to as low as 1.0 MHz. In some cases, auroral hiss is observed below 1.0 MHzBack to article page