Geomagnetically Conjugate Observations of Equatorial Plasma Irregularities From Swarm Constellation and Ground‐Based GPS Stations

Abstract

The near‐polar orbit satellites of Swarm mission provide a good opportunity to investigate the conjugacy of equatorial plasma irregularities (EPIs) since their trajectories at low latitudes are basically aligned with fixed geographical longitude. However, the Swarm in situ electron density occasionally shows EPIs at only one hemisphere at this longitude. In this study, we provide detailed analysis of such EPI events from the in situ electron densities and onboard global positioning system (GPS) measurements of Swarm low pair satellites, and simultaneous GPS data from two geomagnetically conjugate ground stations at the Africa longitudes. The result indicates that when Swam in situ electron density sometime shows EPIs at only one hemisphere, the GPS scintillations are still observed from the Swarm onboard receiver and by the two conjugate ground stations. It implies that the EPIs should generally elongate along the geomagnetic flux tube. More than two‐year statistic results show that the onset time of scintillation in the northern station is on average 16 and 18 min earlier than that in the southern station for September equinox and December solstice in 2015, while for March equinox in 2016 the onset time of scintillation of northern station is about 11 min later than that of southern station, which indicates the asymmetry features of EPIs along the flux tube. Further analysis of nearly three‐year GPS data from two conjugate stations at the Asia longitudes, we find that during solar maximum years the local sunset time plays an important role for causing the difference of onset time of scintillation between two conjugate stations.

Two Typical Ionospheric Irregularities Associated With the Tropical Cyclones Tembin (2012) and Hagibis (2014)

“…Note that a threshold of 0.5 TECU/min has been used for the ground‐based GPS data. Due to the relatively low speed of GPS satellite with respect to a ground‐based station, the ROTI derived from ground‐based receiver mainly reflects the movement of ionospheric irregularity, while the ROTI derived from spaceborne receiver reflects more the irregularity structure along the low Earth orbit satellite track, like Swarm, due to the high speed of low Earth orbit satellite (Luo et al, ). As shown in Figure a, at around 12:30 UT Swarm Ne measurements experienced an abrupt increase (~2 × 10 11 m −3 ) at the 20° MLAT and then fluctuated slightly until 28° MLAT (see the blue region).…”

Combining Swarm Langmuir probe observations, LEO-POD-based and ground-based GNSS receivers and ionosondes for prompt detection of ionospheric earthquake and tsunami signatures: case study of 2015 Chile-Illapel event

“…The existing missions including LPs among the scientific payload are Swarm constellation (Diego et al 2019;Luo et al 2019) and a very recent China Seismo-Electromagnetic Satellite (CSES) (Liu et al 2019). Swarm is the fifth Earth Explorer mission approved in ESA's Living Planet Program, and was successfully launched on 22 November 2013.…”

A Strategy to Mitigate the Ionospheric Scintillation Effects on BDS Precise Point Positioning: Cycle-Slip Threshold Model

“…However, most GNSS receivers only deliver the measurements with 1 s or 30 s interval. In this study, ionospheric scintillation indices ROTI and S 4 are obtained from common geodetic GNSS receivers (30 s interval) [29,30]. The ROTI represents the rate of total electron content (TEC) index.…”

“…In this study, the S 4 index is also estimated by the SI but based on signal-to-noise ratio (S/N 0 ) measurement (30 s interval). The mathematical formula of S 4 is expressed as [29]:…”

“…In addition, it is also seen that the close relationship between the onset time of scintillation occurrence and the local sunset time. The detailed information can be seen in Luo et al [29]. Figure 2 shows four years (2013-16) statistics of scintillation in this region, which is represented by the GPS ROTI index derived from HKST station.…”