Polar cleft structure and SEC associated plasma irregularities observed by Greenland rocket experiment, 1976

In August 1976,two identically instrumented sounding rockets were launched from Danish Meteorological Institute Rocket Range at Sondre Stromiford, Greenland. One rocket (CUSP II) aimed to study the polar ionosphere cusp (or cleft) and the other (SEC II) to study the plasma irregularities in the ionosphere, especially those claimed to be related to the phenomena "Slant E Condition". The detailed cusp structure of electron density and temperature was obtained, showing distinct enhancements in density and temperature around the cusp boundaries. Both flights revealed the plasma irregularities in the ionospheric regions of about 95km to 120km in altitude. Dynamic frequency spectra of these irregularities together with ELF-VLF waves and DC-electric field observations preferably refer to the two stream instabilities.