HR: 0800h
AN: SA41A-1037    [Abstracts]
TI: Comparisons of Measurements at Arecibo of the Gyro Line of Incoherent Scatter with the Theory
AU: * Sulzer, M P
EM: msulzer@naic.edu
AF: Arecibo Observatory, HC 3 Box 53995, Arecibo, PR 00612-9136 United States
AU: Gonzalez, S A
EM: sixto@naic.edu
AF: Arecibo Observatory, HC 3 Box 53995, Arecibo, PR 00612-9136 United States
AB: The gyro line of incoherent scatter is observed in the lower E region at Arecibo during the day. It is weak but still detected easily, and we have recently made measurements of sufficient quality to compare in detail with the predictions of the theory. The first step in a program to obtain useful geophysical information from this scatter is to verify that the results agree with predictions of the theory. Parameters contributing to the characteristics of the line are the electron gyro frequency, the look angle to the magnetic field, the electron density, and the electron temperature. The measurements are made with a long pulse for sensitivity reasons, and so the range resolution is not adequate to determine the location on profiles of density and temperature with sufficient accuracy for comparisons with the theory. Thus it is necessary to find a method to eliminate these two parameters from the comparison. After some time studying the theoretical predictions, it was discovered that the differences between the center frequencies of the lines at two different measurable look angles to the magnetic field are only very weak functions of the density and temperature. That is, although this frequency difference is a function of the electron gyro frequency and the look angle, it is not a strong function of the other two parameters. In effect, this frequency difference is known from the theory and the field parameters and consistency between prediction and the measurement is a check of the theory to a limit determined by the accuracy of the field parameters, the small residual variation due to the density and the temperature, and the random noise in the measurement. After a careful comparison with the data from October 21, 2001, we have determined that the measured difference is too small for agreement with the theory. We are now checking for why this might be so and attempting to make comparisons with other available data sets.
DE: 2443 Midlatitude ionosphere
DE: 2471 Plasma waves and instabilities
DE: 2494 Instruments and techniques
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting