Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers Q. H. Zhou1, Y. T. Morton1, J. D. Mathews2, and D. Janches2,3 1Electrical and Computer Engineering Department, Miami University, Oxford, OH, USA 2CSSL, Pennsylvania State University, University Park, PA, USA 3Arecibo Observatory, Arecibo, Puerto Rico
Abstract. The aspect sensitivity of VHF echoes from field aligned irregularities (FAI)
within meteor trails and thin ionization layers is studied using numerical
models. Although the maximum power is obtained when a radar is pointed
perpendicular to the field line (B), substantial power can
be obtained off the B direction if the ionization
trail/layer is thin. When the FAI length along B is 20 m, the power
observed 6° off B is about 10 db below that
perpendicular to the B direction. Meteoric FAI echoes can
potentially be used to determine the diffusion rate in the mesopause region.
Based on the aspect sensitivity analysis, we conclude that the range spread
trail echoes far off B observed by powerful VHF radars are
likely due to overdense meteors. Our simulation also shows that ionospheric
FAI echoes can have an altitude smearing effect of about 4 km if the
vertical extension of a FAI-layer is around 100 m, which has often been
observed at Arecibo. The altitude smearing effect can account for the fact
that the Es-layers observed by the Arecibo incoherent scatter radar are
typically much narrower than FAI-layers and the occurrence of double
spectral peaks around the Es-layer altitude in FAI echoes.
Citation: Zhou, Q. H., Morton, Y. T., Mathews, J. D., and Janches, D.: Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers, Atmos. Chem. Phys., 4, 685-692, doi:10.5194/acp-4-685-2004, 2004.