This paper describes a coordinated rocket and ground-based study to investigate equatorial spread F irregularities. Measurements by the Jicamarca backscatter radar, ionosondes, and airglow instrumentation and of radio scintillations were correlated with high spatial resolution measurements of electron densities, particle fluxes, and VLF-ELF fields from a rocket probe. Experimentally, we find that (l) very high positive and negative electron density gradients are responsible for the enhanced radar echoes, (2) energetic particles are not part of the spread F phenomena, (3) wave measurements are strongly correlated with the Doppler character of the radar signals, and (4) there is a one-to-one correspondence of the largescale irregularities responsible for scintillations of satellite radio transmissions and ionosonde spread echoes with the small-scale irregularities responsible for the backscatter of VHF radar signals. We present and discuss the implications of the data. A general description of the phenomena and theories attempting to explain spread F, circa 1970, has been given by Farley et al. [1970]. The irregularities which cause the spread ionograms and radio scintillations occur at all heights in the F region and can be observed with the Jicamarca incoherent backscatter radar at all altitudes up to 1200 km. Recently, a number of new and possibly related phenomena have been observed, including intense soft particle fluxes [Heikkila, 1971], strong VLF emissions [Laaspere and Semprebon, 1974], enhanced optical emissions [Leoasseur and Blamont, 1973; Meier and Weller, 1975], and abnormal ion composition and flow [Hanson and Sanatani , 1971]. These observations led to a desire to simultaneously measure the vertical profile well into the topside ionosphere of energetic particles, ion composition, the electric and magnetic field components, atmospheric emissions, and the critically important electron density fluctuations. A crucial part of this experiment was to couple these in situ measurements with simultaneous ground-based measurements of scintillations, Jicamarca radar backscattered power and spectra, ionosonde reflections, and optical emissions.Coupling of these techniques provides the data necessary to determine whether the 3-m irregularities detected by the radar are related to the large-scale irregularities observed with ionosondes and scintillations. From these data we also anticipated being able to determine the interrelationships, if any, betweenThe ground-based data reported in this paper were obtained from several installations which together with the equipment utilized are shown in Table 1. The locations of these sites are shown in Figure 1. The launch site permits rockets to be launched along the magnetic field lines or equatorial electrojet. The Anc6n, Huancayo, and Jicamarca observatories were operated by personnel of the Instituto Geofisico del Peru. The range was operated under the authority of the Peruvian government by the instituto and experimental personnel. A nc6n Obseroatory The Anc6n Observa...
