HR: 13:40h
AN: SA43A-01 INVITED    [Abstracts]
TI: PFISR Observations of Gravity Waves in the Thermosphere
AU: * Nicolls, M J
EM: michael.nicolls@sri.com
AF: Center for Geospace Studies, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025,
AU: Vadas, S L
EM: vasha@cora.nwra.com
AF: NorthWest Research Associates Inc., CoRA Division, 3380 Mitchell Lane, Boulder, CO 80301,
AU: Heinselman, C J
EM: craig.heinselman@sri.com
AF: Center for Geospace Studies, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025,
AB: The tracers of atmospheric gravity waves (AGWs) are observed frequently at high latitudes by examining fluctuations in ionospheric parameters measured by incoherent scatter radars, ionosondes, or HF radars (e.g., SuperDARN), and have been studied for decades. These waves are in general thought to be associated with auroral electrojet activity, which impart momentum and energy into the neutral gas through Lorentz forcing and Joule heating. Tropospheric sources may also be a major source of a certain subset of AGWs that reach ionospheric altitudes. The Poker Flat Advanced Modular Incoherent Scatter Radar (PFISR) is a unique tool allowing for the study of the propagation characteristics and source region identification of AGWs. Multi-position measurements with PFISR allow for the direct and nearly unambiguous extraction of AGW parameters, including period, horizontal and vertical wavelengths, and propagation direction and speed [Nicolls and Heinselman, 2007]. This allows for the explicit evaluation of a recently derived AGW dispersion relation [Vadas and Fritts, 2005] that includes the role of kinematic viscosity and thermal diffusivity, important effects in the upper atmosphere, without assumption about horizontal wavelengths. Because this dispersion relation is formulated in the intrinsic frame of reference, PFISR observations of the vertical wavelength of the propagating waves as a function of altitude can be used to obtain altitude profiles of the neutral winds in the direction of the waves [Vadas and Nicolls, 2007]. This technique may allow for the extraction of altitude profiles of F-region winds (including the zonal component) on a regular basis, especially during the daytime when background densities are sufficiently high. In addition, PFISR studies will allow for source region identification using observed AGW amplitudes and wavelengths, which could shed light on the major sources of AGWs at high latitudes. We will show some case studies where PFISR data have been used to extract AGW properties and discuss how PFISR can be used, in combination with other instruments, to better understand AGW generation, propagation, and interaction with the ionosphere.
DE: 2407 Auroral ionosphere (2704)
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 2494 Instruments and techniques
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting