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Characteristics of quasi‐periodic scintillations observed at low latitude
Author(s) -
Patel Kalpana,
Singh Ashutosh K.,
Singh A. K.,
Singh R. P.
Publication year - 2009
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/2008rs003975
Subject(s) - scintillation , ionosphere , fading , physics , latitude , longitude , earth's magnetic field , geomagnetic latitude , amplitude , spectral density , computational physics , geodesy , geology , optics , geophysics , mathematics , magnetic field , channel (broadcasting) , telecommunications , computer science , statistics , quantum mechanics , detector
Quasi‐periodic scintillations are characterized as primary deep fadeout in field strength, associated with regular ringing patterns before and after it. In this paper, observations of quasi‐periodic scintillations using geostationary satellite (FLEETSAT) transmissions operating at frequency 250 MHz at low‐latitude ground station, Varanasi (geomagnetic latitude 14°55′N, longitude 153°59′E), are reported. The results indicate that the quasi‐periodic scintillations are most likely produced by plasma blobs/bubbles present in the E and F regions of the ionosphere which are helpful in identifying the generation mechanism of the associated irregularities. The various characteristic features of the different types of quasi‐periodic scintillations observed at low latitude are discussed for the first time in detail based on a highly comprehensive analysis of longer data sets using autocorrelation, power spectrum, and scintillation index analysis. The computed horizontal scale size of the quasi‐periodic scintillations producing irregularity varies from 100 to 1300 m which shows that the irregularities are of intermediate‐scale sizes. The spectral index obtained from the slopes of power spectrum varies from −2 to −8. All of these observed results are important for identifying the generation mechanism of ionospheric irregularities associated with quasi‐periodic scintillations. The observed fading patterns, especially the modulation of the diffraction patterns (fading envelopes), can be explained by considering an obstacle called radio lens in the ionosphere elongated in one direction. For the first time, we have successfully simulated the amplitude versus time plots of almost all types of quasi‐periodic scintillation patches and found that our modeled and observed characteristics of quasi‐periodic scintillation patches compare well with each other.