Semiannual Variation of Total Ion Density of Topside Ionosphere Over Indian Equatorial and Low Latitudes

S. Bora¹

Section:Research Paper, Product Type: Journal-Paper
Vol.10 , Issue.2 , pp.20-24, Apr-2022

Online published on Apr 30, 2022

Copyright © S. Bora . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
 

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Abstract :
The total ion density measured by the Retarding potential analyzer (RPA) onboard the satellite FORMOSAT-1 have been analyzed to study the periodicity of the total ion density in the Indian equatorial and low latitude topside ionosphere during peak of the solar cycle 23 (1999 – 2003). The observation reveals the existence of an equinoctial asymmetry. The density is higher in the equinoxes than in the other seasons. This asymmetry is hemisphere dependent. The total ion density is maximum in the March equinox than that in the September equinox in the northern hemisphere. In the southern hemisphere, this pattern is seen in 2000 and 2002. But the March equinoctial density in 2001 is higher than that in the September equinox in the southern hemisphere. An annual and semiannual variation in density during the daytime (10:00-14:00 hrs LT) and nighttime (22:00-02:00 hrs LT) hours is observed. The spectral analysis shows that the power of the annual component is higher in the southern hemisphere while the semiannual component is higher in the northern hemisphere during daytime. But during the nighttime the power of the annual component is higher than that of the semiannual component.

Key-Words / Index Term :
Ionosphere, ionospheric total ion density, annual and semiannual variation, periodicity

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