Thursday, December 16, 2010

More on green fireballs

Hi all

Introduction:

In a recent post I mentioned the just published research work of Stephen Hughes, of the Department of Physics, Queensland University of Technology. He published a paper titled "Green fireballs and ball lightning" which received a large volume of media interest. I have now had a chance to read the entire paper.

Summary:

The paper reviews numerous reports of three green fireballs seen over Queensland on 16 May 2006. It provides data on one luminous green ball seen near ground level, and presents an hypothesis that the passage of one fireball provided energy which created the ground level event.

Detail:

In this post I wish to focus on the luminous green ball observation, rather than the fireball. This is because Hughes writes (page 20) "If confirmed, this hypothesis may be able to explain previously unexplainable UFO sightings and the so-called foo fighters and other aerial phenomenon."

The ground level ball:

Don Vernon, a farmer from Greenmount, 28km south of Toowoomba, Queensland reported the observation "...just after he saw the fireball passing over the Great Divide." (p10.)

After the fireball went out of sight, "...a green ball, about 30cm in diameter was seen rolling down the slope of the range about 1km from the witness...the ball was a soft phosphorescent green...and faintly illuminated the ground out to a few metres...the green ball took between 2 and 3 minutes to roll down the hill...The ball was seen to stop and restart on its journey down the hill and was seen to bounce over a rock..."

The connection:

Hughes writes (p 13.) "The above account is strong evidence for a connection between a meteor and a luminous green ball rolling down a hillside. It is difficult to imagine any other explanation for the luminous ball if it was not connected to the meteor sighting."

"One possibility is that the green ball was some kind of ball lighting." (p13.)

"Could the witness have seen some kind of ball lightning (or some other electrical phenomenon akin to ball lighting) concurrently with the fall of the meteor?" (p14.)

Hughes discusses the possibilities, preferring to argue that "The observations described above are circumstantial evidence that there was some connection between the aerial fireball and ball lightning phenomenon of some kind on the ground." (p15.)

Hypothesis:

"The hypothesis presented in this paper is that the passage of the fireball over Greenmount momentarily reduced the resistance between the ionosphere and ground increasing the flow of current providing energy for the observed ball lightning phenomenon." (p15.)

"It is possible that in the case of the Queensland fireball, some of the plasma surrounding the green fireball broke away from the main object and descended to the Great Divide, possibly following an ionization trail produced by one of the fragments seen to break off the main object. The fact that the ball rolling down the hill was the same colour as the fireball would seem to be evidence in favour of this scenario." (pp15-16.)

Mechanisms:

"There are five possible mechanisms that could have reduced atmospheric resistance (i) thermal ionization; (ii) chemical reaction; (iii) corona discharge; (iv) trail of neutral conducting atoms, e.g. carbon or metal, and (v) fracture charging and tribocharging. It is possible that all five mechanisms could have been involved, with different mechanisms dominant at different altitudes. " (p16.)

Conclusion:

"Momentary electrical connections between the ionosphere and ground created by the passage of a meteor are probably very rare and fleeting. However, the observations described in this paper do provide circumstantial evidence for this and five possible mechanisms are suggested. All five mechanisms probably have to be involved at different points for a conductive path to be maintained even for a few seconds or minutes." (p19.)

My comments:

The ground level, luminous ball observation is certainly anomalous. One point I'd like to make is that at 1km distance (presumably the known distance to the hill the ball moved down) I don't think that it would be possible to accurately estimate the diameter of the ball as 30cm. It is not described as a point source, so apparently had an angular size. However, the paper makes no mention of the witness' estimate of an angular size.

Another question is "how did the witness know the ball was 'rolling' down the slope? " Did they see markings on the ball which allowed them to see it was actually rotating? I think the more appropriate description would be that the ball "descended" the slope.

Despite these two points, the timing of the passage of the fireball and the ball seems to point to a connection.

UFOs:

As to the suggestion that some UFO sightings might be explained by the hypothesis described; I note that even the author himself points out the ionosphere/ground connections "...are probably very rare..." This rarity, and the necessity that "All five mechanisms probably have to be involved at different points..." seems to me, an unlikely explanation for even a small percentage of reported UFOs.

It would be prudent though, to conduct a review of any UFO reports which have in the past occurred close the passage of a fireball. The aim would be to see if one could find any more ground level green ball observations.

From my own memory, and I have collected multiple observations each, from at least three major fireball events, in my own state of South Australia, I don't recall any such green ball sightings.

What do readers think of this?

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