Can the pre-reversal enhancement outside the conventional ±5° geomagnetic latitude equatorial belt be neglected in climatological models?

Résumé fourni par la source

In this study, we analyze ionograms recorded at Malindi (3.1° S, 40.7° E; dipole geom. lat. 6.8° S, Kenya) and Jataí (17.5° S, 51.4° W; dipole geom. lat. 9.1° S, Brazil) from August 2023 to July 2024 to estimate the ionospheric vertical plasma drift associated with the pre-reversal enhancement (PRE). This is the first time that such an intercontinental comparison based on ionosonde data has been conducted, providing a unique opportunity to investigate the ionospheric behavior across widely separated longitudinal sectors. The most striking result is that between October and March, a clear PRE signature is observed at both stations, even though they lie outside the conventional ±5° geomagnetic latitude equatorial belt typically used in climatological studies and for the development of vertical plasma drift models. This finding suggests that limiting such studies and models to the ±5° belt may significantly constrain our understanding of equatorial ionospheric dynamics. Furthermore, the analysis reveals a suppression of the PRE around the June solstice and a marked intensification between October and March, with the effect more pronounced at Malindi than at Jataí. At Malindi, the PRE consistently peaks between 18:00 and 19:00 local time (LT), reaching a maximum value of 30 m/s in October. At Jataí, the PRE peaks slightly later, between approximately 18:30 and 19:15 LT, with a maximum value of 20 m/s in January. We compare ionosonde derived vertical drifts at PRE with a recently developed model based on a combination of magnetometer, satellite and incoherent scatter radar observations as well as the empirical model incorporated within the International Reference Ionosphere that was constructed using satellite data.

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