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On 27 August 1998, at 10:22 UT, an extremely intense gamma ray Rare passed through the solar system. The gamma -ray burst lasted only 5 min and resulted in the ionization of a large portion of the Earth’s night-side upper atmosphere to levels found normally only during the daytime. During this period we were continuously monitoring extremely low frequency (ELF) electromagnetic waves in the range 1-50 Hz, at a new monitoring site established in the Negev Desert, Israel. We have analysed our ELF data, including the Schumann resonances, during this period, and no noticeable changes in the ELF signals are observed as a result of this event. This is very different to observations in the VLF range that showed extreme changes in amplitude and phase resulting from this gamma -ray burst. Theoretical modeling points to three factors that can explain the differences between the VLF and ELF signal responses. (i) different properties of the ELF and VLF signals within the time scale of the gamma -ray burst; (ii) different paths of these signals during the event; and (iii) the different influences of the day/night asymmetry on the propagation of ELF and VLF waves. (C) 2001 Elsevier Science Ltd. All rights reserved.