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Ann. Geophys., 24, 1861-1869, 2006
www.ann-geophys.net/24/1861/2006/
© European Geosciences Union 2006
Gadanki radar observations of daytime E region echoes and structures extending down to 87 km
A. K. Patra1, S. Sripathi2, P. B. Rao3, and R. K. Choudhary4
1National Atmospheric Research Laboratory, Tirupati, India
2Indian Institute of Geomagnetism, New Panvel, Navi Mumbai, India
3National Remote Sensing Agency, Balanagar, Hyderabad, India
4Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Canada
Abstract. Observations of daytime E region echoes extending to altitudes as low as
87 km made using the Gadanki MST radar are presented. The echoing regions
display descending layer resembling the characteristics of tidal winds and
show structures with periods 2–4 min having both positive and negative
slopes. At the center of the layer where strongest SNR is observed, the
velocity is maximum and spectral width is minimum. At altitudes slightly
above and below, where SNR is relatively low, velocity is low but spectral
width is maximum. Daytime observations of echoes extending to such a low
altitude and associated structures akin to nighttime quasi-periodic echoes
throughout the observational period are the most significant results, not
reported earlier from Gadanki and other locations. Other notable results are
large SNR (as high as 15 dB) and spectral width (as high as 70 m/s) at the
bottommost altitudes, where collisional damping of the plasma waves is
significant
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