Open AccessLow‐altitude quasi‐periodic echoes studied using a large database of Gadanki radar observations
Author(s) -
Venkateswara Rao N.,
Patra A. K.,
Rao S. V. B.
Publication year - 2009
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008ja013397
Subject(s) - daytime , equinox , morning , noon , solstice , sunset , radar , altitude (triangle) , atmospheric sciences , meteorology , ionosphere , geology , environmental science , geography , geodesy , physics , latitude , geophysics , astronomy , telecommunications , geometry , mathematics , computer science
In this paper we present studies on low‐altitude quasiperiodic (LQP) echoes based on a large database of Gadanki radar observations. LQP echoes have been observed 33% of the time during daytime and 39% during nighttime. Their occurrence is found to be maximum in the summer (daytime, 58%; nighttime, 57%), followed by the September equinox (daytime, 32%; nighttime, 48%), the March equinox (daytime, 26%; nighttime, 36%), and minimum in the winter (daytime, 25%; nighttime, 26%). Height‐time occurrence of LQP echoes shows two local time maxima: one in the morning (0700–1100 LT) and another in the evening (1900–0000 LT). The most significant results not reported earlier are the large occurrence rate of LQP echoes and the height‐time occurrence maps showing a descending pattern with close resemblance to tidal wind behavior. The Doppler velocities are upward‐northward (downward‐southward) for positive‐ (negative‐) sloped LQP echoes. Also, we find the Doppler spread as high as 200 m s −1 at times underlining the presence of strong plasma turbulence in the collision‐dominated lower E region. These results are discussed in the light of the current understanding of the LQP echoes.