A spherical cap model of the geomagnetic field over southeast Asia from CHAMP and Swarm satellite observations

In this paper, Spherical Cap Harmonic Analysis (SCHA) method was applied to model the geomagnetic field over Vietnam and adjacent area between 15°S 25°N latitude 90°E 130°E in longitude by using magnetic data recorded on CHAMP Swarm satellites. The characteristic parameters of were set at maximum index Kint = 8 for internal fields, spherical cap half-angle θ0 20°. regional areas are modelled two epochs (2007.0 2015.0). Comparison SCHA intensity its time variation with those from IGRF carried out. $$ (E_{F}^{SCHA} ) varies −90 98 nT epoch 2007.0 −139 143 2015.0; however, trends their variations same Vietnam. RMS components ground observations order. amplitude total is about tens greater than