neufer wrote:Ann wrote:
I'd love to know what causes the colors.
This jet lightning is purple to violet near bottom and red at top. Could this be related to blue jets and red sprites, in that the blue jets are lower than the red sprites? Could both these phenomena (or related ones) be seen at different levels of one huge jet?
I'm
guessing that:
- blue jets are from ionized nitrogen atoms that regain an electron after being ionized;
while red sprites are from ionized nitrogen atoms that return to their ground state.
Purple to violet gigantic jets are a combination (and/or) ARGON.
https://en.wikipedia.org/wiki/Aurora 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:
oxygen emissions
- green or orange-red (630.0 nm), depending on the amount of energy absorbed.
nitrogen emissions
- blue: if the atom regains an electron after it has been ionized,
red: if returning to ground state from an excited state.
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.>>
Figure 2: The schematic spectrum of a typical HII region, showing emission lines.
HII denotes a singly ionized hydrogen atom, NII represents a singly ionized
nitrogen atom, and OII and OIII denote singly and doubly ionized oxygen atoms.
Source: http://www.open.edu/openlearn/ocw/mod/o ... =1&id=2462 Thanks, Art, but I'm still confused.
According to the graph and the caption at left, singly ionized nitrogen emits red light on recombination, and this red color is just a little redwards of Hα. What sort of nitrogen emits blue light? I would expect blue light to represent a higher state of excitation than red light. Think of the
Balmer series. Ever higher levels of excitation of the hydrogen atom leads to the emission of ever more shortwave and high-energy photons.
Ann
[quote="neufer"][quote="Ann"]
I'd love to know what causes the colors.
This jet lightning is purple to violet near bottom and red at top. Could this be related to blue jets and red sprites, in that the blue jets are lower than the red sprites? Could both these phenomena (or related ones) be seen at different levels of one huge jet?[/quote]
I'm [b][u]guessing[/u][/b] that:
[list][b][color=#0000FF]blue jets are from ionized nitrogen atoms that regain an electron after being ionized[/color][/b];
while [b][color=#FF0000]red sprites are from ionized nitrogen atoms that return to their ground state[/color][/b].
[b][color=#FF00FF]Purple to violet gigantic jets are a combination (and/or) [u]ARGON[/u].[/color][/b][/list]
[quote=" https://en.wikipedia.org/wiki/Aurora"]
<<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:
oxygen emissions
[list] green or orange-red (630.0 nm), depending on the amount of energy absorbed.[/list]
nitrogen emissions
[list] [b][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].[/b][/list]
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.>>[/quote][/quote]
[float=left][img2]http://www.open.edu/openlearn/ocw/pluginfile.php/66727/mod_oucontent/oucontent/469/37dbf43f/49fb7c7f/s282_2_002i.jpg[/img2][c][size=85]Figure 2: The schematic spectrum of a typical HII region, showing emission lines.
HII denotes a singly ionized hydrogen atom, NII represents a singly ionized
nitrogen atom, and OII and OIII denote singly and doubly ionized oxygen atoms.
Source: http://www.open.edu/openlearn/ocw/mod/oucontent/view.php?printable=1&id=2462[/size][/c][/float] Thanks, Art, but I'm still confused.
According to the graph and the caption at left, singly ionized nitrogen emits red light on recombination, and this red color is just a little redwards of Hα. What sort of nitrogen emits blue light? I would expect blue light to represent a higher state of excitation than red light. Think of the [url=http://www.webassign.net/sercp9/28-p-015.gif]Balmer series[/url]. Ever higher levels of excitation of the hydrogen atom leads to the emission of ever more shortwave and high-energy photons.
Ann