Ionospheric Vertical Plasma Drifts Over South America: Long‐Term Multi‐Instrument Observations and TIEGCM and WACCM‐X Evaluations

We present the first comprehensive multi‐instrument climatological study of quiet‐time equatorial F‐region vertical plasma drifts across South America, a region where the magnetic declination angle varies significantly. Our analysis of well‐established long‐term ground‐based data sets from the Jicamarca incoherent scatter radar spanning 1968–1988, four Brazilian ionosondes (1985–2002), and a ROCSAT‐1 satellite empirical model (1999–2004) highlights strong longitudinal vertical plasma drift variations over the South American sector. These data sets were used to assess the capability of two global first‐principles models, TIEGCM and WACCM‐X, to reproduce the observed patterns. These models represent the measured climatological vertical drift variability, particularly during the day and under moderate‐ to high‐flux conditions. However, their performance is reduced near dawn and dusk. For instance, WACCM‐X often overestimates evening pre‐reversal enhancement (PRE) amplitudes during the solstices, particularly under low solar flux conditions, whereas TIEGCM systematically underestimates the PRE amplitudes in most seasons. Furthermore, both models do not consistently reproduce the local‐time occurrence of the PRE peaks, with occasional offsets of 60 min or more, as well as the dependence of their amplitudes on solar flux. Nevertheless, WACCM‐X provides a relatively good representation of the high‐flux longitudinal patterns of equatorial PRE peak drifts across South America. These findings reveal that, although these models represent substantial progress in reproducing vertical plasma drift observations in this challenging region, continued development will be essential for achieving predictions that more accurately reflect the full complexity of this longitudinal sector.