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Low altitude quasi‐periodic radar echoes observed by the Gadanki VHF radar
Author(s) -
Pan C. J.,
Rao P. B.
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl014331
Subject(s) - daytime , altitude (triangle) , radar , atmospheric sciences , middle latitudes , low latitude , ionosphere , earth's magnetic field , geology , zonal and meridional , doppler radar , sporadic e propagation , range (aeronautics) , latitude , doppler effect , meteorology , geophysics , physics , geodesy , magnetic field , astronomy , telecommunications , geometry , mathematics , materials science , quantum mechanics , computer science , composite material
We report here on the low altitude quasi‐periodic (LQP) radar echoes from low latitude sporadic E layer (Es) observed by the Gadanki (13.5°N, 79.2°E; geomagnetic latitude 6.3°N) VHF radar. The LQP echoes occurred both during daytime and nighttime and are confined to a slowly descending layer with a thickness of about 2–4 km in the height range of 90–100 km. The periods are found to range from tens of seconds to less than about 3 minutes. The Doppler velocities vary over a range of −20 to +20 m/s during daytime and 0 to 10 m/s during nighttime and are known to be sensitive to the layer height, being dominated by the effect of zonal electric field above and meridional neutral wind below a height of ∼97 km for the type 2 irregularities [ Krishna Murthy et al. , 1998]. The spectral widths are found to be of the order of 50 to 75 m/s during daytime and 30 to 60 m/s during nighttime. The LQP echoes reported here are similar to that observed recently over midlatitudes [ Rao et al. , 2000; Urbina et al. , 2000], but distinctly different from the widely reported quasi‐periodic (QP) echoes occurring at higher altitudes (>100 km). The observations are discussed briefly in terms of the potential source mechanisms.