Radar observations of equatorial spread F in a region of electrostatic turbulence

Abstract

Radar observations of a welldeveloped layer of strong equatorial spread F are presented. The scattering cross section, correlation lifetime, and vertical electromagnetic drift velocity of the spread-F irregularities were measured as a function of altitude and time with resolutions of 10 km and I min, respectively. The vertical drift velocities were often 100 m/sec, which is greater by a factor of 3 to 4 times than the vertical drift velocity of the normal undisturbed equatorial ionosphere at similar times. Also the velocity pattern exhibited a turbulent structure, changing sign irregularly every few tens of km and every few minutes, on the average. This observation confirms a recent satellite implication that, based on similarities in their statistical occurrence patterns, electrostatic turbulence and spread F are related. Finally, the finding that the correlation lifetimes of the 3-meter irregularities responsible for radar backscatter vary inversely with the scattering cross section confirms and extends earlier radar results.