Characteristics of Thermospheric Gravity-Wave Induced Wind and Temperature Perturbations Observed by All-Sky Imaging Fabry-Perot Spectrometers

Abstract:

External sources of energy and momentum force thermospheric wind and temperature perturbations to occur over a wide range of spatial and temporal scales. Such forcing can originate both from above due to space weather or from below due to perturbations propagating upward. Acoustic gravity waves play an important role in the responses to such forcing, especially at the smallest spatial and temporal scales. However, while wave responses are most likely ubiquitous, their relative importance as a function of the scale size and height distribution of the forcing is not well characterized observationally. Here we use data from ground-based all-sky imaging Fabry-Perot interferometers in Alaska and Antarctica to measure thermospheric wind and temperature responses to a number of forcing events. These instruments record Doppler spectra of auroral and airglow optical emissions at wavelengths of 630 nm and 558 nm, from which we can infer winds and temperatures at altitudes of roughly 240 km and 110-150 km respectively. In particular, under favorable conditions, height variation of the 558 nm emission allows us to infer altitude profiles of winds throughout the E-region. These data allow us to determine how the overall flow patterns respond to sudden impulsive forcing events such as substorms. Further, by high pass filtering, we can extract the wave perturbations excited by these forcing events. In this presentation we will illustrate these techniques, and examine several forcing events, along with the resulting waves and changes to the wind fields at mesoscales and larger. The relative importances and altitude distributions of these two response types will be examined in the context of the forcing that drove them.