The Brazil/Guará Equatorial Spread F Campaign: Results of the large scale measurements

The Guará campaign equatorial spread F rocket was launched from Alcântara, Brazil, on 14 October 1994 at 1955 LT (2255 UT) into an active topside spread F event. Spread F plasma irregularities observed up to 822 km altitude correlate well with plumes observed simultaneously with a coherent backscatter radar. Matching 1–10 km features in the rocket and radar data over the altitude range 300–800 km implies an eastward drift speed of ∼ 110 m/s, versus 95 m/s at 400–500 km based on radar interferometry. Combining these two measurements implies an average upward drift of 30 m/s for the highest altitude structures. The amplitude difference between low‐ and high‐altitude 10‐km density structures, if attributed to temporal effects, implies an effective diffusion coefficient (decay time constant) of 500–1000 m²/s (2‐4×10−4 s−1), which agrees with previous estimates from other techniques and supports the idea that the decay of spread F turbulence occurs in a scale‐independent manner.