Detection of transient ELF emission caused by the extremely intense cosmic gamma-ray flare of 27 December 2004
Article first published online: 21 APR 2011
Copyright 2011 by the American Geophysical Union.
Geophysical Research Letters
Volume 38, Issue 8, April 2011
How to Cite
2011), Detection of transient ELF emission caused by the extremely intense cosmic gamma-ray flare of 27 December 2004, Geophys. Res. Lett., 38, L08805, doi:10.1029/2011GL047008., , , , , , , , and (
- Issue published online: 21 APR 2011
- Article first published online: 21 APR 2011
- Manuscript Accepted: 24 FEB 2011
- Manuscript Revised: 21 FEB 2011
- Manuscript Received: 4 FEB 2011
 We report on the first clear detection of transient Extremely-Low-Frequency (ELF) signal caused by an extremely intense cosmic gamma-ray flare. On 2004 December 27, the brightest gamma-ray flare ever recorded was observed by numerous satellites. A transient ELF emission observed at Moshiri and Onagawa in Japan exactly coincided with the peak time of the flare, and its wide pulse width of ∼40 ms disfavors the possibility of lightning origin. Furthermore, the two horizontal components of ELF magnetic field data recorded at Esrange in Sweden showed clear transient Schumann resonance waveforms. The source direction determined by the Lissajous method roughly corresponds to the subflare point. The chance probability that a sprite occurs within 30 ms of the peak flare time is ∼0.025%, which again clearly excludes the sprite origin. Thus, a bright cosmic gamma-ray flare is a new source of transient ELF radio signals observed on the Earth, although the emission mechanism needs to be clarified in future.