TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 61 (No. 4), pp. 411-430, 2009

The spread F Experiment (SpreadFEx): Program overview and first results

D. C. Fritts1, M. A. Abdu2, B. R. Batista2, I. S. Batista2, P. P. Batista2, R. Buriti3, B. R. Clemesha2, T. Dautermann4, E. de Paula2, B. J. Fechine2, B. Fejer5, D. Gobbi2, J. Haase4, F. Kamalabadi6, B. Laughman1, L. M. Lima7, H.-L. Liu8, A. Medeiros3, P.-D. Pautet2,5, D. M. Riggin1, F. São Sabbas2, J. H. A. Sobral2, P. Stamus1, H. Takahashi2, M. J. Taylor5, S. L. Vadas1, and C. M. Wrasse9

1NorthWest Research Associates, Colorado Research Associates Division, Boulder, CO
2Instituto Nacional de Pesquisas Espaciais (INPE), São José dos Campos, Brazil
3Universidade Federal de Campina Grande, Campina Grande, Paraíba, Brazil
4Purdue University, West Lafayette, IN
5Utah State University, Logan, UT
6University of Illinois, Urbana, IL
7Universidade Estadual da Paraíba, Campina Grande-PB, Brazil
8National Center for Atmospheric Research, Boulder, CO
9IP&D—Universidade do Vale do Paraíba—UNIVAP, São José dos Campos—SP, Brazil

(Received July 27, 2007; Revised February 13, 2008; Accepted June 3, 2008; Online published May 14, 2009)

Abstract: We performed an extensive experimental campaign (the spread F Experiment, or SpreadFEx) from September to November 2005 to attempt to define the role of neutral atmosphere dynamics, specifically wave motions propagating upward from the lower atmosphere, in seeding equatorial spread F and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures were also collected by GOES 12 and the GUVI instrument aboard the TIMED satellite. Initial results of our analyses of SpreadFEx and related data indicate 1) extensive gravity wave (GW) activity apparently linked to deep convection predominantly to the west of our measurement sites, 2) the presence of small-scale GW activity confined to lower altitudes, 3) larger-scale GW activity apparently penetrating to much higher altitudes suggested by electron density and TEC fluctuations in the E and F regions, 4) substantial GW amplitudes implied by digisonde electron densities, and 5) apparent direct links of these perturbations in the lower F region to spread F and plasma bubbles extending to much higher altitudes. Related efforts with correlative data are defining 6) the occurrence and locations of deep convection, 7) the spatial and temporal evolutions of plasma bubbles, the 8) 2D (height-resolved) structures of plasma bubbles, and 9) the expected propagation of GWs and tides from the lower atmosphere into the thermosphere and ionosphere.
Key words: Equatorial spread F, plasma instabilities, plasma bubbles, plasma bubble seeding, thermospheric gravity waves.

Corresponding author E-mail: dave@cora.nwra.com

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