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Ann. Geophys., 26, 1865-1876, 2008
www.ann-geophys.net/26/1865/2008/
© European Geosciences Union 2008
Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde
D. V. Phanikumar1, A. K. Patra1, C. V. Devasia2, and G. Yellaiah3
1National Atmospheric Research Laboratory, Gadanki, India
2Space Physics Laboratory, VSSC, Trivandrum, India
3Department of Astronomy, Osmania University, Hyderabad, India
Abstract. In this paper, we present seasonal variation of E region field-aligned
irregularities (FAIs) observed using the Gadanki radar and compare them with
the seasonal variation of Es observed from a nearby location SHAR.
During daytime, FAIs occur maximum in summer and throughout the day, as
compared to other seasons. During nighttime, FAIs occur equally in both
summer and winter, and relatively less in equinoxes. Seasonal variations of
Es (i.e. ftEs and fbEs) show that the daytime
activity is maximum in summer and the nighttime activity is maximum in
equinoxes. No relation is found between FAIs occurrence/SNR and
ftEs/fbEs. FAIs occurrence, however, is found to be
related well with (ftEs−fbEs). This aspect is
discussed in the light of the present understanding of the mid-latitude Es-FAIs
relationship. The seasonal variations of FAIs observed at Gadanki are
compared in detail with those of Piura, which show a significant difference in
the daytime observations. The observed difference has been discussed
considering the factors governing the generation of FAIs.
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