The Variation of Counter-Electrojet Current at the Southeast Asian Sector during Different Solar Activity Levels

Studies on counter-electrojet currents (CEJ) using ground data revealed that this current could occur simultaneously among locations are less than 30° longitude apart. In our work, the symmetricity of CEJ variation between west and east Southeast Asia, separated by ~25°, was preliminarily examined according to its types: morning (MCEJ) afternoon (ACEJ). Since most past studies had overlooked occurrence after dusk, monitoring period also extended from 18:00 21:00 LT, namely, post-sunset depletion (PSD). The magnetometer station in Davao, Philippines (DAV) Langkawi, Malaysia (LKW) were chosen represent parts. EEJ index (i.e., EUEL) over periods solar cycle 24 (2008–2018) utilized specifically during magnetically quiet days (Kp < 3). As result, both parts symmetrically showed MCEJ ACEJ positively negatively correlated with F10.7 index. Contrarily, asymmetrically prominent west. types varied season, especially for (at high level), Equinox J-solstice. Post-sunset (PSD) activity independent, as no correlation observed observation. PSD season except Equinox, where it Our finding level part.