Abstract The oceanic tidal magnetic field, mainly driven by the circular orbital motion of the Moon, is an essential part of the time‐varying geomagnetic field. The previously adopted time‐harmonic (TH) base worked well in fitting the primary tidal field, but extracting the other weaker modes like the was difficult with only a single satellite. The tidal field, although it can be derived fortuitously by the gradient data set relying on the side‐by‐side measurements of Swarm, remains a significant challenge in single satellite measurement. Here, we introduce the ephemerides predictor (EP) base, which corrects the Moon's eccentric orbit, to study the tidal fields based on the pre‐processed data set of China Seismo‐Electromagnetic Satellite (CSES) and Swarm‐Alpha. Our results suggest that the EP base is able to derive the tidal fields of both and when the gradient data set is unavailable.
Ma et al. (Mon,) studied this question.