Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx) D. C. Fritts1, S. L. Vadas1, D. M. Riggin1, M. A. Abdu2, I. S. Batista2, H. Takahashi2, A. Medeiros3, F. Kamalabadi4, H.-L. Liu5, B. G. Fejer6, and M. J. Taylor6 1NorthWest Research Associates, CoRA Division, Boulder, CO, USA 2Instituto Nacional de Pesquisas Espaciais (INPE), San Jose dos Campos, Brazil 3Universidade Federal de Campina Grande. Campina Grande. Paraiba. Brazil 4University of Illinois, Champaign, IL, USA 5National Center for Atmospheric research, Boulder, CO, USA 6Utah State University, Logan, UT, USA
Abstract. The Spread F Experiment, or SpreadFEx, was performed from September to
November 2005 to define the potential role of neutral atmosphere dynamics,
primarily gravity waves propagating upward from the lower atmosphere, in
seeding equatorial spread F (ESF) and plasma bubbles extending to higher
altitudes. A description of the SpreadFEx campaign motivations, goals,
instrumentation, and structure, and an overview of the results presented in
this special issue, are provided by Fritts et al. (2008a). The various
analyses of neutral atmosphere and ionosphere dynamics and structure
described in this special issue provide enticing evidence of gravity waves
arising from deep convection in plasma bubble seeding at the bottomside F
layer. Our purpose here is to employ these results to estimate gravity wave
characteristics at the bottomside F layer, and to assess their possible
contributions to optimal seeding conditions for ESF and plasma instability growth rates.
We also assess expected tidal influences on the environment in which
plasma bubble seeding occurs, given their apparent large wind and
temperature amplitudes at these altitudes. We conclude 1) that gravity waves can achieve
large amplitudes at the bottomside F layer, 2) that tidal winds likely control
the orientations of the gravity waves that attain the highest altitudes and
have the greatest effects, 3) that the favored gravity wave orientations
enhance most or all of the parameters influencing plasma instability growth rates,
and 4) that gravity wave and tidal structures acting together have an even
greater potential impact on plasma instability growth rates and plasma bubble seeding.
Citation: Fritts, D. C., Vadas, S. L., Riggin, D. M., Abdu, M. A., Batista, I. S., Takahashi, H., Medeiros, A., Kamalabadi, F., Liu, H.-L., Fejer, B. G., and Taylor, M. J.: Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx), Ann. Geophys., 26, 3235-3252, doi:10.5194/angeo-26-3235-2008, 2008.