Open Access

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

  • D. C. Fritts16Email author,
  • M. A. Abdu26,
  • B. R. Batista26,
  • I. S. Batista26,
  • P. P. Batista26,
  • R. Buriti36,
  • B. R. Clemesha26,
  • T. Dautermann46,
  • E. de Paula26,
  • B. J. Fechine26,
  • B. Fejer56,
  • D. Gobbi26,
  • J. Haase46,
  • F. Kamalabadi66,
  • B. Laughman16,
  • L. M. Lima76,
  • H. -L. Liu86,
  • A. Medeiros36,
  • P. -D. Pautet26, 56,
  • D. M. Riggin16,
  • F. São Sabbas26,
  • J. H. A. Sobral26,
  • P. Stamus16,
  • H. Takahashi26,
  • M. J. Taylor56,
  • S. L. Vadas16 and
  • C. M. Wrasse96
Earth, Planets and Space200961:BF03353158

Received: 27 July 2007

Accepted: 3 June 2008

Published: 14 May 2009


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 GWactivity confined to lower altitudes, 3) larger-scaleGWactivity 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 Fplasma instabilitiesplasma bubblesplasma bubble seedingthermospheric gravity waves