OBSERVATIONS OF THE MESOSPHERE AND LOWER THERMOSPHERE ANGULAR SPECTRUM WITH AN MF RADAR AT WUHAN

Atmospheric angular spectrum is one of the significant features of the atmospheric radio scatterrers. Echoes scattered from the electron irregularities in the mesosphere and lower thermosphere can be used to measure horizontal winds and electron densities with the MF radar at Wuhan. Configured with spaced antenna mode and full correlation analysis techniques, Wuhan MF radar can measure the life time and scale of the irregularities routinely as well. Using these data, the atmospheric angular spectrum can be estimated with both a spectral width method and a space correlation method. The former method gives the upper limit of the angular spectrum, while the latter gives estimations close to the true angular spectrum. The observational data on February 9, 2001 are used to estimate the angular spectrums with these two methods.Results show that the angular spectrum increase slightly with increasing height with a minimum of 6 at 68km and a maximum of 11 at 90km. Its mean value is 9.2.Data at 86km level from Feb. 4 to 10, 2001 are used to give mean daily variations that have a maximum in the daytime and minimum in the nighttime.