Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

# UNCLASSIFIED

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6. The peak intensity of the optical emissions is determined primarily by the removal of the thundercloud charge and its altitude. A vertically striated fine structure of sprites often repeatedly occur in the same place in the sky.

7. Effect on RF Propagation At least one researcher has considered red sprites to comprise an infinite vertical slab of plasmas with the ability to backscatter in the VHF/MF RF Bands. The sprite plasma conducting columns are known to produce wide-angle scattering of VLF signals. Further, rapid onset and rapid decay perturbations of sub-ionisphere propagation occurs. The sprite luminosity decays at a much faster rate than the perturbations. Propagation ducting is probably a by-product. Ground-based radar has been used to observe the effect of sprites on propagation in the vicinity of chaff, using both monostatic and bi-static configurations. Hence, sprite effects may be seen on radar.

## TERRESTRIAL GAMMA FLASHES (TGFs)

8. A new phenomenon (discovered in the 1990s), known as TGFs, are probably also related to atmospheric lightning. However, the time-duration of TGF (estimated at up to 250 $ \mu $sec) is too short for human observation, which possibly limits at 280 $ \mu $sec and is not, therefore, pursued further in the UAP context (the reader is referred to the Working Paper on After-Images).

## BLUE JETS

9. Blue Jet vertical velocities are $ \sim 1 0 0 \mathrm {k m . s e c}^{-1} $ at about 40-50km altitude. Another, competitive, phenomenon （'Blue Starters'）may also occur.

## POSSIBLE UAP LINKS

10. Although the field 'trigger' levels and current flows involved in finally ionising the atmosphere to produce sprites and blue jets in visible form are large (assuming all other field conditions and particle conditions are ready), it is postulated that a situation could exist where the charged atmospheric conditions are at the point of transition in which an added potential might cause a trigger to occur. This has been briefly investigated because a ship's Master reported a visual UAP event when his radar was first switched-on (in the Baltic Sea). It is assumed, since this occurred on a merchant ship, that the RF was I Band (standard 9375MHz maritime search).

## EXTERNAL ENERGISATION

11. The phenomenon is a gas ionisation process for which, when the right threshold conditions exist an additional field is required to trigger the event. It is believed that, for example, a remote, rather than close-by lightning charge could reach the pre-charged volume and cause the glow to be triggered. A short bibliography is at the end of this paper. Since the initial quantification of the effect is quite recent, the following key attributes are taken from the best available (and most relevant to this study) published papers. Further work would be needed to confirm the postulation that a radar (or laser in some cases) could cause the ionisation to occur, thus making a pre-charged but hitherto invisible mass become visible to the human eye. Although the possibility might be linked with sprites/blue jets it is recognised that the 'added' energy available from terrestrial (or airborne) sources will be low in comparison with the huge energy levels in electrical storms. However, the principle is established that any highly charged gas could finally reach ionisation point by the