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

This thesis, an investigation of the mesosphere and the lower thermosphere at northern high latitudes observed with the 557.7 nm (green line) emission from O(1S) by the Wind Imaging Interferometer (WINDII) on NASA's Upper Atmosphere Research Satellite that was launched in 1991 and operated until 2005, is composed of two parts. The first part is a study of the auroral response to magnetospheric precipitating electrons at 90-120 km altitude using a statistical approach that compared high (1993) and low (1996) solar flux years; the second part deals with the observation of supersonic bursts with enhanced O(1S) emission rate observed at 72-82 km altitudes during summer daytime in years of 1995-1996 and its association with other summer phenomena.;For supersonic burst analysis, individual interferograms were examined to evaluate the Doppler shift of the wind velocity. Normally the wind velocity other than in the summer daytime is less than 100 ms-1 below 90 km, for which the averaged O(1S) emission rate arises from dayglow (daytime airglow); these profiles have a peak value of 35 kilo-Rayleigh (kR) at 90 km, rapidly decreasing to 10 kR as low as 70 km. But, during summer daytime in the PMC season (June-August) interferograms at tangent heights of 72-82 km for isolated bins have a large phase shift with respect to the higher altitude normal aurora, corresponding to high velocities of 600-1500 ms-1 (1.5≤ Mach number < 5), accompanying an enhanced O(1S) emission rate (150 kR, horizontally integrated), of which occurrence rate exceeds 40% above 65°N.;The O(1S) emission rate is identified as produced by accelerated electrons in a strong electric field. Theory suggests that an electric field of 25-168 Vm-1 is required to generate a supersonic burst in a velocity of 825 ms-1 forced by ion-neutral collisions at 74-85 km, along with apparent PMC peak altitudes in background profiles.;Coincidences in space and time between supersonic bursts and the space-based lightning detection observed at a wavelength of 777.4 nm were found in a limited number of cases. The lightning detection has the highest occurrence frequency (2-3.5%) and optical energy (1 Jm-2 sr-1 mum-1) during high latitude summer daytime, which is different from ground-based lightning detection resulting in lower occurrence rate at higher latitude. These results may support mesospheric lightning existing at summer high latitude during daytime. The electric field is thus proposed as originating from mesospheric lightning ignited by daytime sprites at high latitude in summer. Confirmation of the existence of daytime sprites at high latitude is provided through the observation of "chirps" in infrasound emissions [Liszka and Enell, 2007]. Sprites may also be triggered by meteors and so frequently occur in the absence of lightning [Liszka and Enell, 2007]. Sprites are electrical gas discharge luminous phenomena occurring in the mesosphere usually above thunderstorm at low-mid latitude.;For the auroral analysis, precipitated particle input is observed with DMSP-F10 and -F12/SSJ4 satellite instruments from which total energy and average energy are obtained. During the daytime (SZA ≤ 90°) the auroral atmospheric response has a good correlation with electron energy input with auroral production rates of 1.2 and 1.6 kR erg-1 cm2s, for years 1993 and 1996, respectively, but this relation breaks down beyond chi=90°. It is suspected that night-time thin sheet auroral profiles are not correctly inverted for this limb-viewing imager. The dependence of auroral emission rate on solar illumination conditions is consistent with earlier work by Newell and others but the clear dependence on solar zenith angle has not been demonstrated before.;In summary, this study suggests for the first time that during high latitude summer daytime mesospheric lightning is associated with observations of a supersonic burst of enhanced O(1S) emission rate.