Evaluating the impact of a tilted eccentric dipole model on ionospheric simulations over the South American sector under quiet geomagnetic conditions

Abstract

This work presents the fi rst comprehensive evaluation of the SUPIM‑INPE ionospheric model using the tilted eccentric dipole (ED) magnetic fi eld configuration, compared with the tilted centered dipole (CD), and validated against observational data of the F2‑layer critical frequency (foF2) that is a key parameter for understanding ionospheric behavior. Simulations were carried out using two ED configurations: one implemented in single precision and the other in double precision to minimize computational rounding and truncation errors and improve numerical stability. Both configurations were tested over fi ve ionospheric stations across South America: Belém (1.43°S, 48.44°W), São Luís (2.60°S, 44.20°W), Cachoeira Paulista (22.70°S, 45.00°W), Tucumán (26.90°S, 65.40°W), and Santa Maria (29.73°S, 53.80°W). Model outputs were compared with ionosonde data from these stations for geomagnetically quiet days during both high (18 January 2014 and 9 May 2024) and moderate (7 and 31 January 2014, 30 January 2023, 21 and 22 April 2023) solar activity conditions. Model performance was evaluated using the Mean Absolute Error (MAE), Mean Relative Error (MRE), and the coefficient of determination (R2). Our results indicate that the double‑precision ED configuration achieves better agreement with observations, highlighting the importance of both a more realistic representation of the geomagnetic fi eld and the reduction of numerical errors in magnetic fi eld geometry and coordinate transformation routines.