[1] Gamma radiation observed in space has been associated with lightning flashes in thunderstorms. These special flashes do not appear to be the large and energetic positive ground flashes that also produce sprites. Considerations of gamma ray attenuation in air indicate that such flashes may not produce gamma radiation at sufficient altitude to enable their escape to space. High-altitude intracloud lightning, most prevalent in the tropics where the tropopause is also high, may be a necessary source.Citation: Williams, E., et al. (2006), Lightning flashes conducive to the production and escape of gamma radiation to space,

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[1] Lightning and thundercloud systems leading to the generation of sprites were examined on the basis of analyses on the interrelation among radar reflectivity, lightning, and static electric field during the winter of 2004/2005 in the Hokuriku area of Japan. Eleven cases from the observed fifteen sprite events exhibit similar characteristics, so we present a typical case study of the thundercloud system. The analysis results are summarized as follows: (1)

[1] VHF, LF, and ELF lightning events, thunderstorms, and surface electric fields related to sprites were observed simultaneously during the winter of 2004/2005 in Hokuriku, Japan. The analysis of these observations enables us to investigate the relationship among sprites, lightning characteristics, and thunderstorm structure just before sprite genesis. Typical winter sprite parent thunderstorms had a mesoscale cloud area with small, embedded convective cells. Positive charges responsible for sprites tend to reside in the upper part of the thunderstorms; only a few positive charges were assumed to be located in the lower part. The total amount of positive charges removed by a sprite-producing flash from the upper and lower parts of the thunderstorms were estimated to be approximately 100 C and as large as 300∼400 C, respectively. Active thunderstorms with lightning accompanied by transient currents tended to generate simple sprites; more complex sprites were excited by lightning with continuing currents, which were generated by a few active thunderstorms and thunderstorms with precipitating stratiform clouds. VHF sources related to sprites can be found in the range of 5 to 72 km. The range of displacement between a sprite element and the corresponding positive cloud-to-ground lightning discharge or the first VHF source was 6∼30 km, and the bottom of the sprite bodies was located between 66 and 74 km. On the basis of these results, we deduced that the complexity of sprite morphology might be attributed to the differences in lightning characteristics.

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Abstract. The data on radio telemetry links (for water information) at VHF/UHF in Hokkaido are used to investigate the rate of disturbances on radio links (or connection failure) and its association with a huge earthquake, Tokachi-oki earthquake on 26 September 2003. Especially, the telemetry links at the Tokachi region closest to the earthquake epicenter, showed a significant increase in disturbances on radio links two weeks to a few days before the earthquake on the basis of analysis during a long interval from 1 June 2002 to 3 November 2007 (over 5 years). We suggest that these severe disturbances in VHF/UHF telemetry links are attributed to the generation of seismogenic VHF/UHF radio noises (emissions). Based on this idea, we have estimated that the intensity of these seismogenic emissions is on the order of 10-19 dB µV/m. Finally, the present result was compared with other physical parameters already obtained for this earthquake.

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