Using the data from our experiments on the IMP-6 (Explorer 43) satellite, we have examined over 200 type III bursts at kilometric wavelengths, including 16 bursts which were accompanied by >18 keV electron events with sharp onsets, in a search for the electrostatic waves which, according to theory, should be the primary source of type III bursts. No electrostatic waves of sufficient intensity to generate the type III bursts by any of the wave-wave scattering thc~ric~ ~hich produce the second harmonic of the plasma frequency, have been found.
Discussion
Young: What E field strength is implied by a 2 mV signal? Kellogg: 2 mV signal implies l~2/8~rNkT = 10 9. R. Smith: Calculations require that the threshold for the oscillating two stream (OTS) be 10 -4= E2/8~rNkT which agrees with observed radio brightness temperature. This is much higher than the observed 2 mV level in ES waves.
Melrose: What is the growth time? Kellogg: 1 calculate a growth time of 5(/(/ seconds: 50 seconds with the factor of 10 due to 47r steradians.
Melrose: When the velocity range of the rising spectrum shifts, the interaction region shifts and you get exponential growth for a limited time which is probably much less than the 500 seconds you quote for the growth time. It seems consistent with the data to expect negligible growth.
Kellogg:
The point is that the growth rates are small; we seem to agree. R. Smith: Can wave turbulence (anomalous resistivity) increase the plasma impedance and affect the measured signals? Anomalous resistivity due to ion turbulence has a peak near ~pe where you are trying to measure the Langmuir oscillations.
Kellogg:
The antenna is not a matched impedance detector. It should rather act as a voltmeter. Gurnett: In our experiment, the different antenna lengths give consistent results for plasma oscillations. There are problems at short wavelengths but otherwise the signal is linearly proportional to the antenna length.