GNSS-RO observed lower-ionospheric electron density: Morphologies driven by magnetospheric and ionospheric processes

Global observations from newly available GNSS-RO (radio occultation) constellations allow a detailed mapping of the lower-ionospheric electron density (N_e) transition from magnetospherically-driving auroral electron precipitation to ionospherically-driving photoionization processes. We applied our N_e retrieval algorithm to the COSMIC-1, COSMIC-2 and Spire GNSS-RO constellations, and obtained monthly N_e maps for every 2-hourly time interval. We found that at high latitudes the N_e distribution from auroral electron precipitation is correlated better with the magnetic field in the magnetosphere (e.g., at one Earth radius R_e), compared to the field in the lower ionosphere (e.g., 100 km). At low-to-middle latitudes, the D/E-region N_e is strongly modulated by solar photoionization and ionospheric magnetic-field pitch angle. Both polar and low latitude distributions reveal a significant longitudinal variation along the same magnetic field pitch angle. It remains as a challenging research topic to fully understand what processes drive these large longitudinal variations at the same pitch angle. Under NASA’s Commercial Smallsat Data Acquisition (CSDA) program, there are ~15,000 GNSS-RO profiles per day from the Spire constellation. With the combined Spire and COSMIC-2 (~6000 profiles per day) data, one will be able to resolve spatiotemporal spectra of these longitudinal variations and further quantify the relative importance of magnetospheric and ionospheric processes, as well as the forcings from the lower atmosphere.