Topside ionosphere effective plasma scale height characterization through CSES-01 satellite Langmuir Probes observations

The topside ionosphere embraces the region extending from the F2-layer electron density peak to the overlying plasmasphere. In this region the electron density monotonically decreases at a vertical rate driven by the plasma scale height, which in turn depends on both the plasma chemical composition and the physical state. Since an accurate and thorough knowledge of the plasma chemical and physical properties at these altitudes is not available with the required spatial and temporal coverage, an effective plasma scale height is usually inferred from topside electron density measurements and used for empirical modelling purposes.

In this work, we aim at characterizing the effective plasma scale height (H₀) above the F2-layer peak  through in-situ electron density (N_e) observations by Langmuir Probes (LPs) on-board the China Seismo-Electromagnetic Satellite (CSES-01). Additional information is given by the International Reference Ionosphere (IRI) model. CSES-01 is a sun-synchronous satellite flying with an orbital inclination of 97.4°, an altitude of ~500 km, and descending and ascending nodes are at ~14 local time (LT) and ~02 LT, respectively. Calibrated CSES-01 LPs N_e data recorded in the years 2019-2021 provides the information in the topside ionosphere, while IRI provides the N_e values at the F2-layer peak (NmF2) for the same time, latitude, and longitude sounded by CSES-01. These two N_e set of values are used as anchor points to infer H₀ through the topside representation given by the NeQuick model. By exploiting the CSES-01 dataset for the years 2019-2021 we deduced the global H₀ behavior for daytime (~14 LT) and nighttime (~02 LT) conditions, for low solar activity conditions. Results obtained with CSES-01 observations are compared and validated with corresponding ones provided by COSMIC-1 radio occultation measurements for similar diurnal and solar activity conditions.