Sprites, Jets, and Elves

[jjohnson]

Here's an older link to an Astronomy Picture of the Day, Nov 11, 1995, http://antwrp.gsfc.nasa.gov/apod/ap951111.html captioned

Recently two new types of lightning have been verified: red sprites and blue jets. These atmospheric discharges occur very high in the Earth's atmosphere - much higher than the familiar form of lightning. Red sprites appear red in color and go from the tops of clouds to as high as the ionosphere - an ionized layer 90 kilometers above the Earth's surface. They last only a small fraction of a second. The existence of red sprites has been suggested previously, but only in 1994 were aircraft flown above massive thunderstorms with the high speed video equipment necessary to verify these spectacular events. Scientists are unsure of the cause and nature of red sprites.

[italics mine] Unsaid was that "the existence of red sprites has been suggested previously..." was not suggested by scientists, as one might erroneously infer from the context, but by observations and reports by dozens of civilian and military pilots flying at night at high altitudes, "above the weather". Their observations were not taken seriously in the scientific community until the first photos and videos were obtained. It's old hat today, of course.

Jim

[larryduane100]

Another news flash is this interesting item:
http://physicsworld.com/blog/2011/01/th ... atter.html

I had no idea that antimatter was so prevalent! This changes my whole 'big picture'. Why isn't the antimatter reacting with normal matter and causing huge explosions?
larryduane100

[StefanR]

Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.

Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown to be associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.

"These signals are the first direct evidence that thunderstorms make antimatter particle beams," said Michael Briggs, a member of Fermi's Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH). He presented the findings Monday, during a news briefing at the American Astronomical Society meeting in Seattle.
.....
The spacecraft was located immediately above a thunderstorm for most of the observed TGFs, but in four cases, storms were far from Fermi. In addition, lightning-generated radio signals detected by a global monitoring network indicated the only lightning at the time was hundreds or more miles away. During one TGF, which occurred on Dec. 14, 2009, Fermi was located over Egypt. But the active storm was in Zambia, some 2,800 miles to the south. The distant storm was below Fermi's horizon, so any gamma rays it produced could not have been detected.

"Even though Fermi couldn't see the storm, the spacecraft nevertheless was magnetically connected to it," said Joseph Dwyer at the Florida Institute of Technology in Melbourne, Fla. "The TGF produced high-speed electrons and positrons, which then rode up Earth's magnetic field to strike the spacecraft."

The beam continued past Fermi, reached a location, known as a mirror point, where its motion was reversed, and then hit the spacecraft a second time just 23 milliseconds later. Each time, positrons in the beam collided with electrons in the spacecraft. The particles annihilated each other, emitting gamma rays detected by Fermi's GBM.
......
Scientists long have suspected TGFs arise from the strong electric fields near the tops of thunderstorms. Under the right conditions, they say, the field becomes strong enough that it drives an upward avalanche of electrons. Reaching speeds nearly as fast as light, the high-energy electrons give off gamma rays when they're deflected by air molecules. Normally, these gamma rays are detected as a TGF.

But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear out of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It's these particles that reach Fermi's orbit.

http://www.nasa.gov/mission_pages/GLAST ... torms.html

[larryduane100]

I suppose this post should have been in Lightning and TGFs over in Planetary Sciences.
larryduane100

[mharratsc]

But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear out of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It's these particles that reach Fermi's orbit.

If they were able to analyze the geometry of the departure of these electrons and positrons I wonder if they wouldn't discover that they looked very much like a CME on the Sun...

Exploding double-layers, anyone? o.O

[Drethon]

You know, some of those pictures kind of remind me of Lichtenberg figures made in acryllic. Could this be a similar effect to those discharges?

[mharratsc]

To me, ELVE's and 'jellyfish' look like the bottom half of a toroidal ring with the dendritic branching appearing like the bottom half of an hourglass pinch.

What do you suppose one of these things looks like from above? If the atmospheric density above the ELVE were higher and went into glow mode, do you suppose you would see an hourglass morphology to the whole thing? o.O

Edit: In retrospect to the other thread on TGF's... I wonder if the space above these ELVE's doesn't look like a CME loop going up and popping.

I wonder which, if any?

[GaryN]

Gamma ray beams, and not just bursts or flashes.

Thundercloud "accelerator" fires gamma-ray beam
Physicists in Japan claim to have the best evidence yet that thunderclouds can act as high-energy particle accelerators for seconds or even minutes at a time.

http://physicsworld.com/cws/article/news/31092

[keeha]

Two nice video representations of this process at the link.

NASA: NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space

Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.

Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown to be associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.

...Scientists long have suspected TGFs arise from the strong electric fields near the tops of thunderstorms. Under the right conditions, they say, the field becomes strong enough that it drives an upward avalanche of electrons. Reaching speeds nearly as fast as light, the high-energy electrons give off gamma rays when they're deflected by air molecules. Normally, these gamma rays are detected as a TGF.

But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear out of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It's these particles that reach Fermi's orbit.

...The GBM has detected gamma rays with energies of 511,000 electron volts, a signal indicating an electron has met its antimatter counterpart, a positron.

...Fermi's Gamma-ray Burst Monitor detected the signal of positrons annihilating on the spacecraft -- not once, but twice. After passing Fermi, some of the particles reflected off of a magnetic "mirror" point and returned.

From the pdf:

1. Electric fields near the top of the storm create an upward-moving avalanche of electrons. When their paths are deflected by molecules in the air, these electrons emit gamma rays, the highest energy form of light.

2. When gamma-ray energy collides with electrons, they accelerate to near the speed of light. Some gamma rays pass near the nuclei of atoms. When this happens, the gamma ray transforms into an electron and its antiparticle, a positron.

These high-energy electrons and positrons escape into space by spiraling along Earth's magnetic field.

[keeha]

I noticed too late to remove the above post it is already posted here:
http://www.thunderbolts.info/wp/forum/phpB ... =30#p45033

Mods, feel free to wipe out these last two posts.

[Maxwell Jennings]

If anyone is looking for the original 2007 National Geographic article link I posted, it was moved to:

http://news.nationalgeographic.com/news ... rites.html

...but the link to the cool video in the article isn't working. I sent a query to alaska.edu for the updated link if it still exists.

[StevenJay]

I was going to start a new thread with this, but then thought it might fit right here.

NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space
Is it just me, or does antimatter seem to be getting more press than usual these days?

[mharratsc]

Wow, that article was right out of a current day textbook.

The young lady said that they think the TGF created a gamma ray, which grazed an atom that freed an electron and a 'positron'. BOTH of these energized particles spiralled (mm-hmm) up a "magnetic field line" (represented as a 2-d ring around a 3-d modelled Earth ) which the Fermi satellite just 'happened' to be sitting in.

Apparently, one of these 'positrons' struck an electron in the body of Fermi, both of which then annihilated, causing Fermi to become a gamma ray emitter for a split second itself, which its own detectors picked up.

Anyone think that there were more than a few assumptions made in that analysis?

I rolled my eyes alot during that one, actually.

[StefanR]

A study of the possibility of sprites in the atmospheres of other planets

Yoav Yair,1 Yukihiro Takahashi,2 Roy Yaniv,1,3 Ute Ebert,4,5 and Yukihiro Goto6
Received 28 November 2008; revised 29 March 2009; accepted 4 June 2009; published 4 September 2009.

[1] Sprites are a spectacular type of transient luminous events which occur above
thunderstorms immediately after lightning. They have shapes of giant jellyfish, carrots, or
columns and last tens of milliseconds. In Earth’s atmosphere, sprites mostly emit in
red and blue wavelengths from excited N2 and N2
+ and span a vertical range between
50 and 90 km above the surface. The emission spectra, morphology, and occurrence
heights of sprites reflect the properties of the planetary atmosphere they inhabit and are
related to the intensity of the initiating parent lightning. This paper presents results of
theoretical calculations of the expected occurrence heights of sprites above lightning
discharges in the CO2 atmosphere of Venus, the N2 atmosphere of Titan, and the H2-He
atmosphere of Jupiter. The expected emission features are presented, and the potential of
detecting sprites in planetary atmospheres by orbiting spacecraft is discussed.

5. Discussion
[19] Model calculations predict the appearance of sprites
in the upper atmospheres of Venus and Jupiter on the basis
of reasonable assumptions on the amount of charge that may
be present in the hypothetical thunderclouds in their atmospheres.
The resultant spectral emissions for sprites in the
atmospheres of other planets can be searched for by orbiting
spacecraft observing the night side of the planet toward the
limb, as was practiced during the MEIDEX sprite campaign
from the space shuttle [Yair et al., 2003] and as being
operationally conducted by the ISUAL instrument on board
the FORMOSAT-2 satellite [Kuo et al., 2005; Cummer et
al., 2006]. In these missions, sprites were recorded above
the Earth’s limb from ranges of 1800–3000 km. This is a
consequence of the low absorption of sprite light by the
atmosphere that enabled enough photons to reach the
onboard detectors. During the MEIDEX, the measured
brightness of sprites was in the range of 0.3–1.7 mega-
Rayleigh (MR; one Rayleigh is equal to 7.96 104 photons
s1 m2 sr1) in the 665 ± 50 nm range and 1.44–1.7 MR
in the 860 ± 50 nm range [Yair et al., 2004], typical of
emissions of the N21P group.
[20] For Venus, the Japanese Planet-C mission [Nakamura
et al., 2007; Takahashi et al., 2008] is designed to carry the
Lightning and Airglow Camera (LAC) which will be used
to observe lightning on Venus even if they are less bright by
a factor of 100 compared to terrestrial flashes, when viewed
from a 100 km altitude. The LAC will have multispectral
capabilities and will cover the oxygen lines in 777.4 nm (OI,
related to lightning) and in 552.5 nm [O2 Herzberg II],
557.7 nm [OI] and 630.0 [OI], which are airglow emissions.
Since the field of view is 16, it is highly likely that any
sprite emission above the cloud tops will be detected by the
instrument as it observes the limb. The fact that no optical
emissions from Venus lightning had been thus far reliably
detected means that they may be weak or completely hidden
owing to absorption by the high-level clouds. This poses an
interesting challenge for the Planet-C mission, namely, to
indirectly infer the existence of lightning in Venus based on
their sprite fingerprints. For Mars, the possibility that corona
or other types of discharges occur inside dust devils and in
large-scale dust storms can be optically verified by sensitive
cameras on board future landers. The possibility that such
discharges can be remotely sensed by orbiting spacecraft is
unclear owing to absorption and obscuration by the dust.
However, if sparks do emanate from the upper parts of the
dust clouds upward into the free atmosphere (upward
flashes had been reported lately on Earth) [Krehbiel et al.,
2008] they can be sought for by nighttime oblique observations
of the dust column, in order to allow escaping
photons to reach the sensor.
[21] The duration and morphology of alien sprites will
strongly depend on the nature of the parent lightning and on
the properties of the atmosphere. Once the critical breakdown
field had been surpassed locally, electron avalanches
can evolve into streamers if the ambient (prebreakdown)
electron density is appropriate; the maximal local field
depends on the temporal behavior of the lighting strokes
and on spatially varying dielectric relaxation times, which in
turn depend on the ambient conductivity. These conditions
are discussed in detail by Pasko et al. [1998, 2002] for
terrestrial sprites. We presently have little information on
these parameters for other planets, yet some insights can be
deduced from observations and laboratory experiments that
use high-speed photography to study electrical sparks and
streamers in various gas mixtures based on similarity laws
and the analogy drawn between sprites and gas discharge
sparks. Stenbaek-Nielsen et al. [2007] and McHarg et al.
[2007] have shown that the tips of sprites are glowing balls
that move rapidly (107 m s1.) and typically brighten as
they travel up or down, with brightness exceeding 60 MR.
The same structure was seen at the tips of streamers
produced in laboratory experiments [Ebert et al., 2006].
Recently, Briels et al. [2006] reported on the properties of
streamers with diameters varying gradually between 0.2 and
2.5 mm, as recorded by an iCCD camera with nanosecond
resolution. In another work Briels et al. [2008] showed that
similarity laws apply for the morphology of streamers at
varying gas densities, and Nijdam et al. [2008] used the
same system to study the 3-D structure and the branching of
streamers. In an appropriate vacuum chamber, such experiments
can be replicated in the appropriate planetary gas
mixtures, in order to elucidate the nature of sprites occurring
in these atmospheres. Present measurements in pure nitrogen
and pure argon already indicate that streamer properties
(inception, width, length, branching) largely depend on gas
composition. This will be a subject for future research.

http://homepages.cwi.nl/~ebert/YairJGR09.pdf

[mharratsc]

Need to point these guys at the authors of that paper you linked in the Aurora on Mars thread, Stefan. They could put 2 + 2 together and arrive at a pretty clear picture, I think.