Climatology of the Occurrence Rate and Amplitudes of Local Time Distinguished Equatorial Plasma Depletions Observed by Swarm Satellite. Issue 4 (13th April 2018)

• Record Type: Journal Article
• Authors: Wan, Xin; Xiong, Chao; Rodriguez‐Zuluaga, Juan; Kervalishvili, Guram N.; Stolle, Claudia; Wang, Hui
• Is Part Of: Journal of geophysical research. Volume 123:Issue 4(2018)
• Page Start: 3014
• Page End: 3026
• Publication Date: 2018-04-13
• Subjects: equatorial plasma depletion -- swarm LP -- depletion amplitude -- climatology -- postmidnight; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA025072
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: In this study, we developed an autodetection technique for the equatorial plasma depletions (EPDs) and their occurrence and depletion amplitudes based on in situ electron density measurements gathered by Swarm A satellite. For the first time, comparisons are made among the detected EPDs and their amplitudes with the loss of Global Positioning System (GPS) signal of receivers onboard Swarm A, and the Swarm Level‐2 product, Ionospheric Bubble Index (IBI). It has been found that the highest rate of EPD occurrence takes place generally between 2200 and 0000 magnetic local time (MLT), in agreement with the IBI. However, the largest amplitudes of EPD are detected earlier at about 1900–2100 MLT. This coincides with the moment of higher background electron density and the largest occurrence of GPS signal loss. From a longitudinal perspective, the higher depletion amplitude is always witnessed in spatial bins with higher background electron density. At most longitudes, the occurrence rate of postmidnight EPDs is reduced compared to premidnight ones; while more postmidnight EPDs are observed at African longitudes. CHAMP observations confirm this point regardless of high or low solar activity condition. Further by comparing with previous studies and the plasma vertical drift velocity from ROCSAT‐1, we suggest that while the F region vertical plasma drift plays a key role in dominating the occurrence of EPDs during premidnight hours, the postmidnight EPDs are the combined results from the continuing of former EPDs and newborn EPDs, especially during June solstice. And these newborn EPDs during postmidnight hours seem to be less related to the plasma vertical drift. Plain Language Summary: Practically, the equatorial plasma depletions are always related to transionospheric radio signal interruption. However, this work reveals that the higher occurrence of the structure does not always coincident with the higher occurrence of Global Positioning System signal loss, but the larger depletion amplitude is required. From the scientific perspective, the mechanism behind postmidnight equatorial plasma depletions is varying, and this work provides proofs on some aspects about postmidnight equatorial plasma depletions. Key Points: Amplitude of EPDs is rarely related to the occurrence rate but to the background electron density and GPS signal loss Postmidnight EPDs are consistent phenomenon throughout the full solar cycle Evidences supporting the postmidnight EPDs are the combined results from the continuing of former EPDs and newborn ones