[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,

[1] The atmospheric response to precipitating auroral electrons under varying conditions of solar illumination is investigated using a statistical approach with respect to magnetic local time (MLT), solar zenith angle (c), and geomagnetic latitude (MLAT) in the northern high-latitude region. Vertical profiles of daytime auroral O( 1 S) emission rate are obtained from UARS/WINDII measurements by removing the airglow components. These are compared with precipitating electron and proton input observed with DMSP-F10 and -F12 SSJ4 from which total energy and average energy are obtained. In order to investigate the solar flux effect, 2 a of data are examined, 1993 (high solar flux) and 1996 (low solar flux). Total electron energy flux increases with increasing solar zenith angle from 40°to 160°so that the energy flux during nighttime is much greater than in the daytime. During the daytime (c 90°) the auroral atmospheric response correlates well with electron energy input yielding auroral production rates of 1.2 and 1.6 kR erg À1 cm 2 s, but this relation breaks down beyond c = 90°. It is suspected that nighttime thin sheet auroral profiles are not correctly inverted for this limb-viewing imager. A strong anticorrelation is found between the altitude of peak auroral volume emission rate and the average precipitating electron energy with slopes of 12.1 km keV À1 and 5.7 km keV À1 for 1993 and 1996, respectively. The dependence of auroral emission rate on solar illumination conditions is consistent with earlier work by Newell et al. (1996b) and others, but the clear dependence on solar zenith angle has not been demonstrated before.