## 4 Conclusions  
This study observed CEJ over solar cycle 24 in eastern and western parts of Southeast Asia. It was apparent that MCEJ and ACEJ were solar activity dependent, with positive and negative correlations with the F10.7 index, respectively, in both parts, with remarkable symmetry. The asymmetricity of CEJ dominance (i.e., MCEJ in the east and ACEJ in the west) was probably due to local effects, which calls for a detailed study specifically in Southeast Asia to ascertain such effects in the sector, since the reported observation in the past was limited to only in the Indian sector. The seasonal variation of CEJ at different solar activity levels exhibit east-west symmetrical behavior during Equinox season for the greatest MCEJ occurrence and J-solstice at high solar activity level for ACEJ. This observation thus confirmed the mechanism that was proposed in past studies that involves atmospheric tides and stationary planetary waves. However, ACEJ at low solar activity level was excluded due to the corresponding percentage between Equinox and solstice month that might be caused by insufficient data. Upon extending the observation period to detect occurrences after dusk, it was found that PSD was solar activity independent in both parts and varied symmetrically by seasons. This event was also prominent during Equinox, except in the west during high solar activity level. In this preliminary PSD observation, we proposed that the appearance of PSD could be related to the equatorial plasma bubble phenomenon as the evening CEJ could have shifted to dusk time. This proposal will be confirmed in a future study on the CEJ-EPB relationship.  
Figure 9: (**a**) Seasonal variation of PSD in the east (DAV) over solar cycle 24 (left \(y\)-axis) alongside F10.7 index (right \(y\)-axis), and (**b**,**c**) its dominance at low and high solar activity levels. Information in (**d–f**) is similar to (**a–c**) but for the west (LKW).  
**Author Contributions:** Conceptualization, N.I.M.R. and N.S.A.H.; data curation, A.Y. and T.U.; funding acquisition, N.S.A.H. and M.A.; investigation, N.I.M.R.; methodology, N.I.M.R., N.S.A.H. and B.R.; project administration, N.S.A.H. and M.A.; supervision, N.S.A.H. and M.A.; validation, N.S.A.H. and K.A.Y.; visualization, N.I.M.R.; writing--original draft, N.I.M.R.; writing--review and editing, N.S.A.H., K.A.Y., T.U. and B.R. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was funded by the grant GUP-2019-053 from Universiti Kebangsaan Malaysia. MAGDAS was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI grant no. 268022. A.Y. was supported in part by the JSPS Core-to-Core Program (B. Asia-Africa Science Platforms), Formation of Preliminary Center for Capacity Building for Space Weather Research and JSPS KAKENHI grant 15H05815.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors would like to extend their gratitude to all members of the MAGDAS project including MAGDAS Malaysia team and Malaysian Space Agency (MYSA) for their cooperation and contribution to this study. F10.7 data that were obtained from the GSFC/SPDF OMNIIWeb interface.  
**Conflicts of Interest:** The authors declare no conflict of interest.