Red sprites, secondary jets and newly discovered green afterglow called "ghosts" triggered by red sprites. A dozen vibrant red sprites were recorded on this evening and only two events had the green afterglow. More technical info below...
CURRENT "GREEN AFTERGLOW" THEORIES
I'm leaning towards it being an interaction with the airglow layer which is lowered due to gravity waves. I know that in heavy thunderstorms , gravity waves form in the airglow layer with deeper peaks and troughs and that the strongest nightglow emissions occur mostly in a relatively thin layer of atmosphere between 85 and 95 kilometers (53 and 60 miles) above the Earth’s surface. Little emission occurs below this layer since there’s a higher concentration of molecules, allowing for dissipation of chemical energy (via collisions rather than light production). Likewise, little emission occurs above that layer because the atmospheric density is so low that there are too few light-emitting reactions to yield an appreciable amount of light. I think that gravity waves perhaps caused deeper troughs pushing this layer of atmosphere associated with airglow down enough to interact with the sprite tops. Then it's a matter of only the most energetic sprites triggered within this trough produce the effect. It would explain why not all bright sprites have this and how not all tips have it in one bright event. Essentially like a tiger elve version of a sprite. Tiger-sprite. My pic of gravity waves in Texas airglow shows similar color.
Melissa Allin, P.E.
It is known that lightning strikes split diatomic oxygen into atomic oxygen and with the recombining of some of these O atoms with O2, ozone is created. Theory: The green afterglow at the upper edge of a preceding red sprite could be production of O3 at upper levels of the stratosphere and could be refeeding the ozone.
The green afterglow appears to happen when the red sprite is noticeably brighter. The sprite’s red comes from excited nitrogen. Excited O can emit light in 3 wavelengths: green, orange-red, and red. Is the more brilliant red from the addition of atomic oxygen in the red range? Atomic O with H2O can produce hydroxyl radical (OH). OH also emits red and has previously been associated with “red airglow” at altitudes ~85 km. This also could contribute to the brighter red.
Theory: Green afterglow captured in videos of red sprites is like green airglow associated with the aurorae but generated via electrical excitation instead of solar radiation. In certain instances of the creation of atomic O and hydroxyl radicals, there is an increase in production of these oxidizers making them visible on HD videography. If correct, what are the parameters that stack to create these abundant events, and can we facilitate their occurrence? Hydroxyl radicals are key in cleansing non-CO2 GHGs from the atmosphere. Their production is suppressed the more CO2 and methane increase in the atmosphere. Questions: Do these events happen over areas where there is a discernable difference in atmospheric composition (i.e. greater amounts of O2 containing molecules, greater amounts of GHGs? certain topography? arid areas that have water vapor incursion due to the supercell?)
A plasma is typically a hot soup of ions and electrons which are thermalized and STUPID hot. But it's possible for certain conditions (radio frequency heating or extremely rapid electrical discharges, like in a sprite) for only electrons in a plasma to become thermalized, while ions and neutral atoms remain relatively cold. This is a nonthermal plasma or non-equilibrium plasma. Since electrons have an extremely tiny mass, a nonthermal plasma stores little heat energy and has a very high extinction rate. What I think has happened here is a hot region of the sprite (a largely nonthermal plasma) has persisted for a period of time long enough to heat and partially thermalize much heavier ions and neutral atoms in the mesosphere. Ion extinction rates for these heavier species (looks like oxygen ions from the color) are much lower because they store a lot of thermal energy, so the glow persists much longer. Best guess at least!
If this is indeed a new discovery, it would be nice if we could give it a name that is descriptive and in the theme of sprites, elves, and trolls. Perhaps an acronym... GhOST Green emissions from Oxygen in Sprite Tops ??? What about the "H" Hue is redundant... Deep thoughts.
Sprite Music: by Pecos Hank
End Music "La male'diction de la danse du poulet"