“…To improve the time and spatial resolutions, the SymH index of 1-minute resolution was developed (Iyemori et al,1992) using the H-component data from up to 6 stations of MLS ~70º. The Dst and SymH indices have been used for studying not only the geomagnetic storms (e.g, Russell et al, 1973;Burton et al, 1975a;Gonzalez et al, 2011;Gopalswamy et al, 2015;Yermolaev et al, 2021;Balan et al, 2021;Manu et al, 2022Manu et al, , 2023 but also the disturbed upper atmosphere, ionosphere and magnetosphere (e.g., Fuller-Rowell et al, 1994;Manuucci et al, 2005;Tulasiram et al, 2010). For reviews, see Akasofu (1981Akasofu ( , 2021, Proless (1995), Daglis (1997), Luhr et al (2017) and Zong et al, (2021).…”