Summer high‐latitude mesospheric observations of supersonic bursts and O(¹S) emission rate with the UARS WINDII instrument and the association with sprites, meteors, and lightning

Abstract

[1] Supersonic neutral velocities, called supersonic bursts, are observed in localized regions lasting for over 8 s of enhanced O( 1 S) emission rate for tangent altitudes of 73-80 km during summer daytime by the Wind Imaging Interferometer (WINDII) on board the UARS satellite; the occurrence rate is 40% (≥500 m s −1 ) for latitudes above 65°N. These bursts are proposed to be produced by accelerated electrons and ions in a strong electric field. Theory suggests that an electric field of 45 V m −1 is required to generate a typical supersonic velocity of 750 m s −1 forced by ion-neutral collisions at 82 km, the altitude at which polar mesospheric clouds occur. Coincidences in space and time between supersonic velocity profiles and space-based lightning detection observed at a wavelength of 777.4 nm were found in a limited number of cases in high-latitude summer, a region for which the lightning detection has the highest occurrence frequency (2-3.5%) and optical energy (1 J m −2 sr −1 mm −1 ) as a function of month and latitude. The electric field must have sufficient energy to generate atomic emission features, more than for sprites and comparable with tropospheric lightning. Support for the existence of supersonic bursts at high latitude is provided through the observation of "chirps" in infrasound emissions which frequently occur in the absence of tropospheric lightning.Citation: Lee, Y.-S., and G. G. Shepherd (2010), Summer high-latitude mesospheric observations of supersonic bursts and O( 1 S) emission rate with the UARS WINDII instrument and the association with sprites, meteors, and lightning, J. Geophys. Res., 115, A00E26,

Chemical and thermal impacts of sprite streamers in the Earth's mesosphere

“…For the cases of 50 ms and 100 ms driving current (see Figures e and f, respectively) we see a number of variations in the O( 1 S) density between 10 −3 s and 10 −1 s due to direct electron impact dissociative excitation of O 2 (P38). Recent measurements made by UARS [ Lee and Shepherd , ] indicate sudden and significant 557.7 nm optical outbursts from O( 1 S) between 73 km and 87 km in coincidence with lightning flashes (or some seconds after lightning) that could have produced sprites in the upper atmosphere. The transient enhancement of the O( 1 S) concentration (and subsequent sudden optical outbursts) can be produced by electron impact dissociative excitation (e + O 2 → O + O( 1 S) + e) due to the abundant presence of energetic free electrons released by sprite streamer ionization events.…”

“…However, according to Parra‐Rojas et al [], the concentrations of NO and O 3 exhibit a negligible variation due to halos. Moreover, the simulations by Hiraki et al [] predict a substantial increase in the concentration of O( 1 D), and the measurements made by UARS (Upper Atmosphere Research Satellite) indicate a substantial enhancement of O( 1 S) [ Lee and Shepherd , ] due to the possible presence of sprites. Concerning kinetic modeling of sprites, Sentman et al [] developed a kinetic model with more than 800 chemical reactions to study the impact of a streamer pulse with E max =5 E k (where E k is the breakdown electric field, E k / N = 120 Td) and Δ t = 6 μs at 70 km of altitude in the mesosphere.…”

The Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite: A 20 year perspective

“…There is undoubtedly a wealth of data remaining in the Level 1 data that has not been exploited to date. One unusual example was discovered by Lee and Shepherd [2010]. In looking at O( 1 S) daytime low‐altitude Level 1 images, they found occasional bins with high emission rate, having perfectly sinusoidal interferograms with very large phase shifts, large enough to correspond to supersonic winds.…”

Observation of atomic oxygen O(1S) green‐line emission in the summer polar upper mesosphere associated with high‐energy (≥30 keV) electron precipitation during high‐speed solar wind streams

“…The electric field is therefore a strong candidate for the energy source for accelerating both ions and neutrals to extremely high speeds in the D ‐region ionosphere/upper mesosphere. An electric field can be estimated from the speed of neutral or ion using the following equation [ Lee and Shepherd , ]: where q is the electric charge of the electron (1.6 × 10 −19 C), E is the electric field vector (V m −1 ), m i is the mean ion mass (≈31 × 1.6 × 10 −27 kg, based on MSIS‐90 [ Hedin , ]), and v in is the ion‐neutral collision frequency (s −1 ). The equation indicates that an electric field of about 147 V m −1 at 80 km is required to produce a velocity of 750 m s −1 .…”

“…The ice particle formation (subvisible) occurring at ~88 km but with multiple layers (radii <20 nm) detected as PMSE undergoes condensation, sedimentation, and growth and finally appears as PMC with the radii from 20 to 100 nm [ Zadorozhny et al ., ; Rapp and Lübken , ; Hervig et al ., ]. According to Lee and Shepherd [], the PMC occurrence rate is 87% over all profiles above 65°N and supersonic velocity occurrence for ≥500 m s −1 is 40% for July 1996. Thus, in most measurements at high latitude, PMC signature can be observed.…”