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ISSN  2096-3955

CN  10-1502/P

Citation: Abadi, P., Otsuka, Y., Liu, H. X., Hozumi, K., Martinigrum, D. R., Jamjareegulgarn, P., Thanh, L. T, and Otadoy, R. (2021). Roles of thermospheric neutral wind and equatorial electrojet in pre-reversal enhancement, deduced from observations in Southeast Asia. Earth Planet. Phys., 5(5), 387–396.

2021, 5(5): 387-396. doi: 10.26464/epp2021049


Roles of thermospheric neutral wind and equatorial electrojet in pre-reversal enhancement, deduced from observations in Southeast Asia


Space Science Center, Indonesian National Institute of Aeronautics and Space (LAPAN), Bandung, Indonesia


School of Electrical Engineering, Telkom University, Jl. Telekomunikasi No. 1, Kab. Bandung 40257, Indonesia


Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Nagoya, Japan


Department of Earth and Planetary Science, Kyushu University, Fukuoka, Japan


National Institute of Information and Communications Technology, Tokyo, Japan


Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Kyoto, Japan


King Mongkut’s Institute of Technology Ladkrabang, Prince of Chumphon Campus, Chumphon, Thailand


Institute of Geophysics, Vietnamese Academy of Science and Technology, Hanoi, Vietnam


University of San Carlos, Cebu, Philippines

Corresponding author: P. Abadi,

Received Date: 2021-01-11
Web Publishing Date: 2021-09-10

Previous studies have proposed that both the thermospheric neutral wind and the equatorial electrojet (EEJ) near sunset play important roles in the pre-reversal enhancement (PRE) mechanism. In this study, we have used observations made in the equatorial region of Southeast Asia during March–April and September–October in 2010–2013 to investigate influences of the eastward neutral wind and the EEJ on the PRE’s strength. Our analysis employs data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite to determine the zonal (east-west direction) neutral wind at an altitude of ~250 km (bottomside F region) at longitudes of 90°–130°E in the dusk sector. Three ionosondes, at Chumphon (dip lat.: 3.0°N) in Thailand, at Bac Lieu (dip lat.: 1.7°N) in Vietnam, and at Cebu (dip lat.: 3.0°N) in Philippines, provided the data we have used to derive the PRE strength. Data from two magnetometers — at Phuket (dip lat.: 0.1°S) in Thailand and at Kototabang (dip lat.: 10.3°S) in Indonesia — were used to estimate the EEJ strength. Our study is focused particularly on days with magnetically quiet conditions. We have found that the eastward neutral wind and the EEJ are both closely correlated with the PRE; their cross-correlation coefficients with it are, respectively, 0.42 and 0.47. Their relationship with each other is weaker: the cross-correlation coefficient between the eastward neutral wind and the EEJ is just 0.26. Our findings suggest that both the eastward neutral wind and the EEJ near sunset are involved in the PRE mechanism. Based on the weak relationship between these two parameters, however, they appear to be significantly independent of each other. Thus, the wind and the EEJ are likely to be influencing the PRE magnitude independently, their effects balancing each other.

Key words: equatorial ionosphere, thermosphere-ionosphere couple, pre-reversal enhancement, thermospheric neutral wind, equatorial electrojet

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Roles of thermospheric neutral wind and equatorial electrojet in pre-reversal enhancement, deduced from observations in Southeast Asia

P. Abadi, Y. Otsuka, HuiXin Liu, K. Hozumi, D. R. Martinigrum, P. Jamjareegulgarn, Le Truong Thanh, R. Otadoy