neufer wrote: ↑Wed Sep 18, 2019 6:40 pm
BDanielMayfield wrote: ↑Wed Sep 18, 2019 5:38 pm
Psnarf wrote: ↑Wed Sep 18, 2019 4:12 pm
Am I correct in postulating the tip of the bright bolt marks the boundary between the stratosphere and ionosphere? Is the violet color from ionized nitrogen?
I wondered about the source of the colors also. The green would be ionized Oxygen, right? What about the red?
https://en.wikipedia.org/wiki/Aurora#Auroras_and_the_atmosphere wrote:
<<Auroras result from emissions of photons in the Earth's upper atmosphere, above 80 km, from ionized nitrogen atoms regaining an electron, and oxygen atoms and nitrogen based molecules returning from an excited state to ground state. They are ionized or excited by the collision of particles precipitated into the atmosphere. Both incoming electrons and protons may be involved. Excitation energy is lost within the atmosphere by the emission of a photon, or by collision with another atom or molecule:
nitrogen emissions: blue or red; blue if the atom regains an electron after it has been ionized, red if returning to ground state from an excited state.
oxygen emissions: green or orange-red, depending on the amount of energy absorbed. Oxygen is unusual in terms of its return to ground state: it can take three-quarters of a second to emit green light and up to two minutes to emit red. Collisions with other atoms or molecules absorb the excitation energy and prevent emission. Because the highest atmosphere has a higher percentage of oxygen and is sparsely distributed such collisions are rare enough to allow time for oxygen to emit red. Collisions become more frequent progressing down into the atmosphere so that red emissions do not have time to happen, and eventually, even green light emissions are prevented. This is why there is a color differential with altitude; at high altitudes oxygen red dominates, then oxygen green and nitrogen blue/red, then finally nitrogen blue/red when collisions prevent oxygen from emitting anything. Green is the most common color. Then comes pink, a mixture of light green and red, followed by pure red, then yellow (a mixture of red and green), and finally, pure blue.>>
https://en.wikipedia.org/wiki/Sprite_(lightning) wrote:
<<Sprites or red sprites are large-scale electrical discharges that occur high above thunderstorm clouds, or cumulonimbus, giving rise to a quite varied range of visual shapes flickering in the night sky. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground.
Sprites appear as luminous reddish-orange flashes. They often occur in clusters above the troposphere at an altitude range of 50–90 km. Sporadic visual reports of sprites go back at least to 1886 but they were first photographed on July 6, 1989, by scientists from the University of Minnesota and have subsequently been captured in video recordings many thousands of times.
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. Sprites are associated with various other upper-atmospheric optical phenomena including blue jets and ELVES.
Sprites are colored reddish-orange in their upper regions, with bluish hanging tendrils below, and can be preceded by a reddish halo. They last longer than normal lower stratospheric discharges, which last typically a few milliseconds, and are usually triggered by the discharges of positive lightning between the thundercloud and the ground, although sprites generated by negative ground flashes have also been observed. They often occur in clusters of two or more, and typically span the altitude range 50 to 90 kilometres, with what appear to be tendrils hanging below, and branches reaching above.[4]
Optical imaging using a 10,000 frame-per-second high speed camera showed that sprites are actually clusters of small, decameter-sized (10–100 m or 33–328 ft) balls of ionization that are launched at an altitude of about 80 km and then move downward at speeds of up to ten percent the speed of light, followed a few milliseconds later by a separate set of upward moving balls of ionization. Sprites may be horizontally displaced by up to 50 km from the location of the underlying lightning strike, with a time delay following the lightning that is typically a few milliseconds, but on rare occasions may be up to 100 milliseconds.>>
Thanks, Art, very interesting. Am I right to think you are suggesting that nitrogen might cause the blue color of the blue jets, and that oxygen, high up in the atmosphere, might cause the red color of the red sprites?
Ann
[quote=neufer post_id=295348 time=1568832009 user_id=124483]
[quote=BDanielMayfield post_id=295343 time=1568828298 user_id=139536]
[quote=Psnarf post_id=295341 time=1568823149 user_id=129160]
Am I correct in postulating the tip of the bright bolt marks the boundary between the stratosphere and ionosphere? Is the violet color from ionized nitrogen?[/quote]
I wondered about the source of the colors also. The green would be ionized Oxygen, right? What about the red?[/quote][quote=https://en.wikipedia.org/wiki/Aurora#Auroras_and_the_atmosphere]
[float=left][img3=""]https://upload.wikimedia.org/wikipedia/commons/c/c4/Upperatmoslight1.jpg[/img3][/float]<<Auroras result from emissions of photons in the Earth's upper atmosphere, above 80 km, from ionized nitrogen atoms regaining an electron, and oxygen atoms and nitrogen based molecules returning from an excited state to ground state. They are ionized or excited by the collision of particles precipitated into the atmosphere. Both incoming electrons and protons may be involved. Excitation energy is lost within the atmosphere by the emission of a photon, or by collision with another atom or molecule:
[size=125][b]nitrogen emissions: blue or red; [color=#0000FF]blue if the atom regains an electron after it has been ionized[/color], [color=#FF0000]red if returning to ground state from an excited state.[/color][/size]
oxygen emissions: green or orange-red, depending on the amount of energy absorbed.[/b] Oxygen is unusual in terms of its return to ground state: it can take three-quarters of a second to emit green light and up to two minutes to emit red. Collisions with other atoms or molecules absorb the excitation energy and prevent emission. Because the highest atmosphere has a higher percentage of oxygen and is sparsely distributed such collisions are rare enough to allow time for oxygen to emit red. Collisions become more frequent progressing down into the atmosphere so that red emissions do not have time to happen, and eventually, even green light emissions are prevented. This is why there is a color differential with altitude; at high altitudes oxygen red dominates, then oxygen green and nitrogen blue/red, then finally nitrogen blue/red when collisions prevent oxygen from emitting anything. Green is the most common color. Then comes pink, a mixture of light green and red, followed by pure red, then yellow (a mixture of red and green), and finally, pure blue.>>[/quote][quote=https://en.wikipedia.org/wiki/Sprite_(lightning)]
[float=left][img3=""]https://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/BigRed-Sprite.jpg/1280px-BigRed-Sprite.jpg[/img3][/float]
<<Sprites or red sprites are large-scale electrical discharges that occur high above thunderstorm clouds, or cumulonimbus, giving rise to a quite varied range of visual shapes flickering in the night sky. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground.
Sprites appear as luminous reddish-orange flashes. They often occur in clusters above the troposphere at an altitude range of 50–90 km. Sporadic visual reports of sprites go back at least to 1886 but they were first photographed on July 6, 1989, by scientists from the University of Minnesota and have subsequently been captured in video recordings many thousands of times.
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. Sprites are associated with various other upper-atmospheric optical phenomena including blue jets and ELVES.
Sprites are colored reddish-orange in their upper regions, with bluish hanging tendrils below, and can be preceded by a reddish halo. They last longer than normal lower stratospheric discharges, which last typically a few milliseconds, and are usually triggered by the discharges of positive lightning between the thundercloud and the ground, although sprites generated by negative ground flashes have also been observed. They often occur in clusters of two or more, and typically span the altitude range 50 to 90 kilometres, with what appear to be tendrils hanging below, and branches reaching above.[4]
Optical imaging using a 10,000 frame-per-second high speed camera showed that sprites are actually clusters of small, decameter-sized (10–100 m or 33–328 ft) balls of ionization that are launched at an altitude of about 80 km and then move downward at speeds of up to ten percent the speed of light, followed a few milliseconds later by a separate set of upward moving balls of ionization. Sprites may be horizontally displaced by up to 50 km from the location of the underlying lightning strike, with a time delay following the lightning that is typically a few milliseconds, but on rare occasions may be up to 100 milliseconds.>>[/quote]
[/quote]
Thanks, Art, very interesting. Am I right to think you are suggesting that nitrogen might cause the blue color of the blue jets, and that oxygen, high up in the atmosphere, might cause the red color of the red sprites?
Ann