Multiscale properties of the ionospheric electric field in the auroral region from a one-year survey with CSES-01.

We present the results of a study of the electric field properties in the auroral oval (AO) region. We exploit more than one year of electric field measurements taken by the EFD instrument onboard the China-Seismo-Electromagnetic Satellite 01 (CSES-01) spacecraft, orbiting sun-synchronously at around 500 km of altitude inside the Earth ionosphere. To exploit the high temporal resolution of EFD, we devise a new technique that allows to detect the crossing of the AO by CSES-01 using electric field measurements only. This new technique combines a median-weighted local variance measure and Iterative Filtering to automatically isolate high levels of electromagnetic activity caused by, e.g., particle precipitation and Field Aligned Currents (FAC) at auroral latitudes. We validate this new method on few selected orbits against other standard proxies, such as the SWARM single-FAC product and the auroral radiance emission measured by SSUSI onboard the DMSP constellation. Furthermore, we identify ~3 000 orbits (on a dataset of ~10 000) of high geomagnetic activity where CSES either crossed the AO boundary or the polar cap region and characterize the multiscale (down to characteristic electron scales) statistical properties of the electric field. This work represents the first systematic study of the Auroral electric field, with many potential applications to space-weather studies, thanks to the large amount of continuous observations of the ionosphere carried out by CSES-01.