An experimental study of electron thermal runaway in the lower ionosphere
Coco, David Stephen
Gordon, William E.
Master of Science
An ionospheric heating experiment has been performed at the Arecibo Observatory using the 43 MHz incoherent backscatter radar both as a heater and as a diagnostic. Radar pulses up to 9 msec in length were transmitted with 2.5 MW (2.5 x 1^erg/sec) peak: pulse power yielding a peak power flux of approximately 2. x 1 erg/cm sec at 1 km altitude. A 2 microsecond diagnostic pulse offset in frequency from the heating pulse was used to measure the resultant ohmic heating of electrons in the lower ionosphere. Using a model of electron heating and cooling in the lower ionosphere, the ratio of heated electron temperature to unheated electron temperature is calculated as a function of altitude and heating power flux. This model predicts a beam-averaged electron temperature ratio of about 2.25 at 1 km for a transmitted power of 2. MW, pulse length of 9 msec and an antenna efficiency of 5%. When the predicted beamaveraged electron temperature ratios are compared with the observed, the observed are found to be less than the predicted for all values of transmitted power used. Possible sources of the discrepancy between experiment and theory are discussed.