Yuichi Otsuka, Prayitno Abadi, Kornyanat Hozumi, Alif Almahi
We have investigated equinoctial asymmetry of scintillation occurrence and zonal irregularity drift velocity observed with closely-spaced GPS receivers at Kototabang (0.20°S, 100.32°E; geomagnetic latitude 10.6°S), Indonesia during a period from 2003 to 2016, and found that the scintillation occurrence rate is higher in Mar. equinox than in Sep. equinox, and that the eastward drift velocity at post-sunset is higher in Mar. equinox than in Sep. equinox. This result is consistent with previous work done by Otsuka et al. (2006), who have analyzed scintillation and zonal drift velocity data obtained at Kototabang in 2003–2004, and suggests that the eastward drift velocity corresponding to the downward electric field at post-sunset may be related to the pre-reversal enhancement of eastward electric field, which could play an important role in generating plasma bubble. In this study, we have investigated vertical drift velocity by analyzing the ionosonde data obtained near magnetic equator (Chumphon, Bac Lieu, and Cebu) during a period from 2003 to 2016, and found that the upward drift velocity at post-sunset is larger in Mar. equinox than Sep. equinox. We also find that solar activity dependence of the zonal and vertical drift velocities is more clearly seen in Mar. equinox than in Sep. equinox. In order to consider the mechanism causing the equinoctial asymmetry of the drift velocities, foF2 obtained by the ionosondes is also analyzed. We find that foF2 also depends on solar activity more clearly in Mar. equinox than in Sep. equinox, and that foF2 during high solar activity conditions is higher in Mar. equinox than in Sep. equinox. These results suggest that in Mar. equinox, due to high electron density, intense electric field could be generated through the F-region dynamo so that plasma bubble likely occurs. © 2023
Institute for Space‐Earth Environmental Research, Nagoya University, Nagoya, Japan; Research Center for Climate and Atmosphere, Indonesian National Research and Innovation Agency (BRIN), Bandung, Indonesia; School of Electrical Engineering, Telkom University, Kab. Bandung, Indonesia; National Institute of Information and Communications Technology (NICT), Tokyo, Japan; NASA Goddard Space Flight Center, Community Coordinated Modeling Center, Greenbelt, MD, United States; Department of Physics, Catholic University of America, Washington, DC, United States; Department of Atmospheric and Planetary Sciences, Sumatera Institute of Technology (ITERA), Lampung, Indonesia
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