GNSS Ionosphere Sounding of Equatorial Plasma Bubbles

Abstract

Ground- and space-based Global Navigation Satellite System (GNSS) receivers can provide three-dimensional (3D) information about the occurrence of equatorial plasma bubbles (EPBs). For this study, we selected March 2014 data (during solar maximum of cycle 24) for the analysis. The timing and the latitudinal dependence of the EPBs occurrence rate are derived by means of the rate of the total electron content (TEC) index (ROTI) data from GNSS receivers in China, whereas vertical profiles of the scintillation index S4 are provided by COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate). The GNSS receivers of the low Earth orbit satellites give information about the occurrence of amplitude scintillations in limb sounding geometry where the focus is on magnetic latitudes from 20° S to 20° N. The occurrence rates of the observed EPB-induced scintillations are generally smaller than those of the EPB-induced ROTI variations. The timing and the latitude dependence of the EPBs occurrence rate agree between the ground-based and spaceborne GNSS data. We find that EPBs occur at 19:00 LT and they are mainly situated above the F2 peak layer which descended from 450 km at 20:00 LT to 300 km at 24:00 LT in the equatorial ionosphere. At the same time, the spaceborne GNSS data also show, for the first time, a high occurrence rate of post-sunset scintillations at 100 km altitude, indicating the coexistence of equatorial sporadic E with EPBs.

Altitude Distribution of Large and Small‐Scale Equatorial Ionospheric Irregularities Sampled From an Elliptical Low‐Earth Orbit

“…This simultaneous E‐ and F‐region irregularity occurrence has also been noted in more recent work by Ma et al. (2019). Watson and Pedatella (2018a) studied the characteristics of the F‐region plasma irregularities at medium scale sizes (∼2–50 km) using COSMIC measurements and observed an increase in the irregularity intensity and occurrence in the 400–440 km altitude range around 20 to 24 magnetic local time (MLT) in solar active years.…”

“…In an integrated study of concurrent E-and F-region irregularities using a ground-based GNSS receiver and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO measurements, Yang and Liu (2018) showed that while the F-region irregularities occur mainly during 20-03 LT, observed irregularities at higher altitudes were more pronounced during 20-22 LT. Those authors reported the coexistence of sporadic E and EPBs in the F region during post-sunset hours. This simultaneous E-and F-region irregularity occurrence has also been noted in more recent work by Ma et al (2019). Watson and Pedatella (2018a) studied the characteristics of the F-region plasma irregularities at medium scale sizes (∼2-50 km) using COSMIC measurements and observed an increase in the irregularity intensity and occurrence in the 400-440 km altitude range around 20 to 24 magnetic local time (MLT) in solar active years.…”

“…Ma et al. (2019) demonstrated that the EPB occurrence rate estimated using the S 4 index is different from that found using TEC variations. We should also note that there are fewer measurements around 21–22 MLT in our study (Figure 7).…”

Supervised Detection of Ionospheric Scintillation in Low-Latitude Radio Occultation Measurements

“…As one of the causes of radio signal scintillation, regions of ionospheric irregularities in the F-layer, known as Equatorial Plasma Bubbles (EPB), have been investigated with RO measurements, adding a limb-sounding perspective to ground-based measurements. During March 2014 (around the equinox and at the maximum of the 24th solar cycle), COSMIC data corroborated ground-based measurements and showed a higher occurrence of EPBs at the magnetic equator after sunset, at about 450 km and descending to 300 km around midnight [23]. A longer period of evaluation, between 2007 and 2017, showed a similar interval of occurrence of EPBs with peak varying depending on the level of solar activity.…”

An improved method using adaptive smoothing for GNSS tomographic imaging of ionosphere

“…It sets a priori information for each voxel before the iteration begins in the tomographic region. The kth iteration of ART algorithm computes the difference between Y and Y k which is obtain by using the current estimated value X k in Eq (4) [35][36][37]. A correction derived from the difference is distributed over X k to get X k+1 .…”