Lidar observations of mesospheric Fe and sporadic Fe layers at Urbana, IL

Lidar measurements of mesospheric Fe were conducted at Urbana, IL (40 degree N, 88 degree W) during 4 nights in late October 1989. The average Fe abundances, layer centroid heights and rms widths varied between 1.0-2.0x1010 cm-2, 89.0-90.5 km and 3.2-4.1 km, respectively. The peak densities of the layer near 90 km varied between 15-25x103 cm-3. Considerable gravity wave and tidal activity was observed in the Fe profiles. On 3 nights the formation and dissipation of 3 large sporadic Fe (Fes) layers was observed. These are the first observations of this phenomenon. The 2 largest Fes layers formed at 102.4 km and 91.4 km over a period of about 20 min and their widths were approximately 2.3 km FWHM. The peak densities of the Fes layers were as high as 31x103 cm-3 and the abundances were as high as 5.8x109 cm-2. The observations are compared with previous measurements of mesospheric Fe and with recent observations of sporadic Na (Nas) layers