Experimental observations of medium and small scale electrostatic waves associated with ionospheric electron density fluctuations

Abstract

On 18 December, 1995 at 21:17 hrs (LT) an electric field double probe, a Langmuir probe, and a High Frequency Capacitance probe were flown from the equatorial rocket launching station Alcantara (2.31°S; 44.4°W) in Brazil on board a Brazilian SONDA III rocket, for measurements of the height variation of the ionospheric electric field and electron density. The rocket reached an apogee altitude of 557 km and covered a horizontal range of 589 km. Ground equipment monitored the ionospheric conditions during the launch. The rocket passed through several medium-scale plasma bubbles mainly during the downleg. The upleg electron density profile showed a clearly-defined base for the F-region around 300 km, while the downleg profile showed a wide spectrum of electric field and electron density irregularities in this height region as well as in the upper F-region. Spectral analysis of the fluctuations in electron density and electric field clearly indicated sharp spectral peaks at several heights, in most cases associated with each other. This is suggestive of the electrostatic nature of these E-field waves, that may be excited at the onset of plasma instabilities along with waves in electron density.