Swarm Electric Field Instruments, processors and data quality: evolutions, new baseline and scientific highlights

ESA Earth Explorer Swarm mission, launched in November 2013 with the purpose of exploring and understanding the Earth’s interior and its environment, provided significant achievements in the observation of the geomagnetic field, the ionosphere, and electric currents. And it continues contributing to geomagnetism and ionospheric science fields.Each of the three satellites of the Swarm constellations carries onboard a set of instruments to achieve the mission objectives: a Vector Field and an Absolute Scalar Magnetometer (VFM and ASM); three star trackers (STR) for accurate attitude determination and, recently, for energetic particle detection; a dual-frequency GPS receiver (GPSR); an accelerometer (ACC); an Electric Field Instrument (EFI), composed of two Langmuir Probes (LPs) and two Thermal Ion Imagers (TIIs), dedicated to electric field and plasma measurements. The products derived from EFI instruments represent the focus of this work.A defining feature of the Swarm mission is its commitment to continuous improvement. Since its launch, advancements in data processing algorithms have been continuously applied: these updates have not only maintained the good quality of Swarm's measurements but have also allowed the mission to evolve and continue meeting the needs of the scientific community. These refinements served the development of novel Swarm-based data products and services, further broadening the mission’s impact, and allowing it to overcome the initial objectives and go beyond its original scope, such as in the Space Weather field.In December 2025, the most recent baseline has been transferred to operations, delivering updated datasets and evolved products. These algorithm updates greatly impacted the EFI LP products. This work will provide an overview of the improvements applied on Swarm plasma data products: detailed analyses are presented, dedicated to new plasma densities and temperatures parameters, new flags, and other upgrades; comparisons with other L1B and L2 Swarm products are performed; case studies in correspondence of recent main Space Weather events are also displayed, to highlight the innovative application of Swarm to this field.