APOD: Red Sprite Lightning with Aurora (2013 May 22)

[APOD Robot]

Red Sprite Lightning with Aurora

Explanation: What's that in the sky? It is a rarely seen form of lightning confirmed only about 25 years ago: a red sprite. Recent research has shown that following a powerful positive cloud-to-ground lightning strike, red sprites may start as 100-meter balls of ionized air that shoot down from about 80-km high at 10 percent the speed of light and are quickly followed by a group of upward streaking ionized balls. The above image, taken a few days ago above central South Dakota, USA, captured a bright red sprite, and is a candidate for the first color image ever recorded of a sprite and aurora together. Distant storm clouds cross the bottom of the image, while streaks of colorful aurora are visible in the background. Red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side.

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[Ann]

Red Tinkerbell.

Ann

[Boomer12k]

Fascinating....nature's fireworks...such interesting phenomena...


:---[===] *

[PhilT]

Sounds like an explanation for many a UFO sighting

[mister T]

Giant Plasma Space Lobster!!

Cover yourselves in lemon and butter!!

[Beyond]

Interesting comments, i Tink!

[nstahl]

10% of the speed of light is an immense speed for anything with mass, which ionized air certainly has. And it would take a LOT of force to accelerate that air to that speed that fast.

If that kind of force is generated in our upper atmosphere over thunderstorms, that sounds like a dangerous place to be. And it sounds like some fascinating phenomenon is going on right over our heads that we don't understand at all well.

[ta152h0]

Fred Flinstone hit a chunk of flint

[Chris Peterson]

10% of the speed of light is an immense speed for anything with mass, which ionized air certainly has. And it would take a LOT of force to accelerate that air to that speed that fast.

Not so much, I think. When we talk about "ionized air" we're talking about extremely low atomic or molecular densities- only one atom out of millions or billions is actually in an ionized state. So the total mass involved is very small. We're essentially talking about a current flow, and as such, speeds of 0.1c don't seem that extraordinary. The force that propels the ions is created by an imbalanced charge, which would have almost no effect at all on a neutral body like a balloon or space plane in that region.

[neufer]

10% of the speed of light is an immense speed for anything with mass, which ionized air certainly has. And it would take a LOT of force to accelerate that air to that speed that fast.

• I don't believe that the plasma, itself, is moving that fast.
  
  It is rather the excitations within the plasma that travel that fast. (Think of a tsunami, for instance.)

<<Sprites are sometimes inaccurately called upper-atmospheric lightning. However,sprites are cold plasma phenomena that lack the hot channel temperatures of tropospheric lightning, so they are more akin to fluorescent tube discharges than to lightning discharges.>>

[b][color=#0000FF]A glow discharge tube featuring its most important characteristics: (a) An anode at one end and cathode at the other end (b) Aston Dark Space(c) Cathode glow (d) Cathode dark space (also called Crookes dark space, or Hittorf dark space) (e) Negative glow (f) Faraday space (g) Positive column (h) Anode glow (i) Anode dark space.[/color][/b]

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<<The simplest type of glow discharge is a direct-current glow discharge. In its simplest form, it consists of two electrodes in a cell held at low pressure (0.1–10 torr). The cell is typically filled with neon, but other gases can also be used. An electric potential of several hundred volts is applied between the two electrodes. A small fraction of the population of atoms within the cell is initially ionized through random processes (thermal collisions between atoms or with gamma rays, for example). The ions (which are positively charged) are driven towards the cathode by the electric potential, and the electrons are driven towards the anode by the same potential. The initial population of ions and electrons collides with other atoms, ionizing them. As long as the potential is maintained, a population of ions and electrons remains.

Some of the ions' kinetic energy is transferred to the cathode. This happens partially through the ions striking the cathode directly. The primary mechanism, however, is less direct. Ions strike the more numerous neutral gas atoms, transferring a portion of their energy to them. These neutral atoms then strike the cathode. Whichever species (ions or atoms) strike the cathode, collisions within the cathode redistribute this energy until a portion of the cathode is ejected, typically in the form of free atoms. This process is known as sputtering. Once free of the cathode, atoms move into the bulk of the glow discharge through drift and due to the energy they gained from sputtering. The atoms can then be excited by collisions with ions, electrons, or other atoms that have been previously excited by collisions. Once excited, atoms will lose their energy fairly quickly. Of the various ways that this energy can be lost, the most important is radiatively, meaning that a photon is released to carry the energy away.>>

[jm3]

If I understand the caption right, the sprite is occurring high above a presumed powerful ground strike in the storm low on the horizon below. No wonder these are hard to see.

The symmetry is interesting as well, I wonder what would keep the ionized gas contained, even temporarily, in the repeating shapes.

[neufer]

I wonder what would keep the ionized gas contained, even temporarily, in the repeating shapes.

Even at these altitudes the mean free path is only ~3 millimeters.

Moving at ~300 m/s an atom/ion will engage in ~ 10⁶ collisions in ~10 seconds
and thereby random walk only 10³ mean free paths = ~3 meters.

[jambo]

Being from SD, I'm wondering more specifically where this fascinating picture was taken. And for me the image evokes a spider on a stick...

[ta152h0]

looking at the Earth as a Nixie tube

[MargaritaMc]

>>. And for me the image evokes a spider on a stick...

sprite.jpg

[DavidLeodis]

Could someone please inform me what the FMA in FMA Research stands for as it does not seem to be mentioned in the website brought up through the link and I have been unable to fairly readily find out. Based on the year dates seen that website also seems not to have been updated for many years.

The sprite reminds me of illustrations I've seen of the structure of a virus with its head and tail.

[bystander]

Could someone please inform me what the FMA in FMA Research stands for as it does not seem to be mentioned in the website brought up through the link and I have been unable to fairly readily find out.

Forensic Meteorology Associates

[DavidLeodis]

Could someone please inform me what the FMA in FMA Research stands for as it does not seem to be mentioned in the website brought up through the link and I have been unable to fairly readily find out.

Forensic Meteorology Associates

Thank you for that bystander, which is appreciated.

[flash]

red sprites[/url] may start as 100-meter balls of ionized air that shoot down from about 80-km high at 10 percent the speed of light

As Chris and Art point out it is the ionization charge that moves at 0.1c, not the ionized air molecules themselves.

Consider the orientation of the linear features of the sprites: They appear to be angled downward along the surface of an inverted cone (apex up). This would seem to be in correlation with charges travelling downward starting from a point (the apex of the cone). Since the ions all have the same charge (positive? negative?) they mutually repel and so the charges fan out on the way down. Do we know anything about why the previously neutral atoms ionize in the first place? Or why the charges move the way they do? What happens to the opposite charges?

[DavidLeodis]

Nobody has queried this so I may be the only person that was surprised by the statement in the explanation that "Red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side." (my bold text). I've never realised that thunderstorms have a side, though I've probably also never given it any thought!

[ta152h0]

this phenomenon is getting analysed to death, just enjoy it ! Wait a minute, humans are curious creatures by nature, never mind.

[neufer]

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I may be the only person that was surprised by the statement in the explanation that "Red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side." (my bold text). I've never realised that thunderstorms have a side, ...

<<The average thunderstorm has a 24 km diameter.>>

Art Neuendorffer (who went directly from "towering stage" to "dissipating stage.")

[Chris Peterson]

Nobody has queried this so I may be the only person that was surprised by the statement in the explanation that "Red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side." (my bold text). I've never realised that thunderstorms have a side, though I've probably also never given it any thought! :o

Sprites always occur over thunderstorms. I catch them occasionally on my meteor camera- always near the horizon, under clear skies. These sprites are produced by thunderstorms that are a few hundred miles away- typically, over the horizon. If that isn't seeing a storm from the side, I don't know what is!

sprite_20110902_222108_001.jpg (20.37 KiB) Viewed 4356 times

You can see the horizon glow from the lightning that triggered the sprite, but not the lightning itself, or the thunderclouds. The sprites are in completely clear sky. These were only about 80 miles away.

[DavidLeodis]

Thanks neufer and Chris for your replies.

You state Chris "These sprites are produced by thunderstorms that are a few hundred miles away- typically, over the horizon. If that isn't seeing a storm from the side, I don't know what is!". I did not know, which is why I was trying to seek help which you have given but I did not need what seems to be the condescensive tone.

[Chris Peterson]

Thanks neufer and Chris for your replies.

You state Chris "These sprites are produced by thunderstorms that are a few hundred miles away- typically, over the horizon. If that isn't seeing a storm from the side, I don't know what is!". I did not know, which is why I was trying to seek help which you have given but I did not need what seems to be the condescensive tone. :(

Sorry, there was no intent to be condescending at all. The sentence was intended to be purely exclamatory.