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Quiet time short‐period and day‐to‐day variations in E × B drift studied using 150 km radar echoes from Gadanki
Author(s) -
Pavan Chaitanya P.,
Patra A. K.,
Rao S. V. B.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019668
Subject(s) - amplitude , daytime , physics , quiet , day to day , drift velocity , radar , atmospheric sciences , period (music) , diurnal temperature variation , electric field , geodesy , astrophysics , meteorology , geology , optics , operations management , quantum mechanics , computer science , acoustics , economics , telecommunications
In this paper we present short‐period and day‐to‐day variations in E × B drift during low solar and magnetically quiet conditions, based on radar observations of daytime 150 km echoes from Gadanki, India. Short‐period (<100 min) variations in E × B drift show amplitude as large as 7 m s −1 and display large day‐to‐day variation. Spectral analysis reveals that drift velocity fluctuations consist of several components of short periods in the range of 4–100 min. Among these periods, the most frequently occurring periods are 6–60 min. Observations also show that amplitudes of these periods increase with increasing period. Interestingly, signal‐to‐noise ratio (SNR) variations also show periods of 3–19 min, which have also been observed in velocity variations. In addition, amplitudes of the periodic variations in SNR tend to increase with increasing period, which is also similar to those observed in drift velocity fluctuations. No correlation between SNR and velocity variations, however, has been found. Noticeable day‐to‐day variations in drift velocity are found in all seasons, and the variation is as large as ±25 m s −1 . Day‐to‐day variations also show wave‐like features with period of 2–4 days. Observed E × B drift variations of 7 m s −1 at short time scale and 25 m s −1 on a day‐to‐day basis indicate zonal electric field variations of 0.25 mV/m and 0.9 mV/m, respectively. We surmise that quiet time E × B drift variations with periods <100 min and 2–4 days are likely to be the manifestations of gravity wave and planetary wave wind‐induced electric fields, respectively, consistent with those reported earlier.