Radio-tomographic images of postmidnight equatorial plasma depletions

For the first time, equatorial plasma depletions (EPDs) have been imaged in the longitude‐altitude plane using radiotomography. High‐resolution (~10 km) reconstructions of electron density were derived from total electron content (TEC) measurements provided by a receiver array in Peru. TEC data were obtained from VHF/UHF signals transmitted by the Coherent Electromagnetic Radio Tomography (CERTO) beacon on the C/NOFS satellite. EPDs generated premidnight were observed near dawn. On one night, the bubble densities were highly reduced, 100–1000 km wide, and embedded within a layerlike ionosphere. Three nights later, the EPDs exhibited similar features but were embedded in a locally uplifted ionosphere. The C/NOFS in situ instruments detected a dawn depletion where the reconstruction showed lifted EPDs, implying that the postmidnight electric fields raised sections of ionosphere to altitudes where embedded/reactivated fossil EPDs were detected as dawn depletions. Satellites flying under domelike distortions of the ionosphere may observe these distortions as broad plasma decreases (BPDs). Key Points First‐ever radiotomographic reconstructions of equatorial plasma depletions Dawn depletions detected in situ when predawn E fields raise F layer sections Broad plasma decreases detected when satellites fly under the raised sections