HR: 0830h
AN: SA21A-04    [Abstracts]
TI: Can Gravity Waves Seed Spread F?"
AU: * Dewan, E M
EM: edmond.dewan@hanscom.af.mil
AF: AFRL/VSBYB, hanscom AFB., Bedford, MA 01731-3010 United States
AB: Evidence from backscatter radar (Hysell et al. 1990) shows that quasi-periodic "bubbles" or "Equatorial Spread F" (ESF) could be "seeded" by gravity waves having horizontal wavelengths of order100 km at altitudes of around 200km (the bottom of the F-Layer). In this paper two questions will be considered: (a) "Can such waves be generated by thunderstorms in the troposphere such that they can propagate to high altitudes?" and (b) " Can such waves sufficiently overcome viscous damping effects to propagate all the way up to 200 km altitudes? "Based upon simulations by Vadas and Fritts, 2004 and Alexander et al. 1995, it will be shown that mesoscale convective complexes, but not "squall lines", could indeed generate such waves, and that, in agreement with Vadas and Fritts, they could indeed reach a position to directly seed "Spread -F" irregularities. In any case, as will be shown, both types of such waves can certainly easily reach the E Region altitude of 100 km. In principle, therefore, they could seed Spread F through E-field perturbations that map up to the F region in the manner described by Prakash, 1999. It still remains to be experimentally demonstrated that gravity wave sources in the troposphere can trigger ESF.
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2439 Ionospheric irregularities
DE: 2447 Modeling and forecasting
DE: 3384 Waves and tides
SC: SPA-Aeronomy [SA]
MN: 2005 Joint Assembly