Determinations of ionosphere and plasmasphere electron content for an African chain of GPS stations
The confluence of recent instrumentation deployments in Africa with developments for the determination of plasmasphere electron content using Global Positioning System (GPS) receivers has provided new opportunities for investigations in that region. This investigation, using a selected chain of...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-05-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/35/599/2017/angeo-35-599-2017.pdf |
| Summary: | The confluence of recent instrumentation
deployments in Africa with developments for the determination of plasmasphere
electron content using Global Positioning System (GPS) receivers has provided
new opportunities for investigations in that region. This investigation,
using a selected chain of GPS stations, extends the method (SCORPION)
previously applied to a chain of GPS stations in North America in order to
separate the ionosphere and plasmasphere contributions to the total electron
content (TEC) during a day (24 July) in 2011. The results span latitudes from
the southern tip of Africa, across the Equator, to the southern Arabian
Peninsula, providing a continuous latitudinal profile for both the ionosphere
and plasmasphere during this day.<br><br>The peak diurnal vertical ionosphere electron content (IEC) increases from
about 14 TEC units (1 TEC unit = 10<sup>16</sup> electrons m<sup>−2</sup>) at the
southernmost station to about 32 TEC units near the geographic equator, then
decreases to about 28 TEC units at the Arabian Peninsula. The peak diurnal
slant plasmasphere electron content (PEC) varies between about 4 and
7 TEC units among the stations, with a local latitudinal profile that is
significantly influenced by the viewing geometry at the station location,
relative to the magnetic field configuration. In contrast, the peak vertical
PEC varies between about 1 and 6 TEC units among the stations, with a
more uniform latitudinal variation.<br><br>Comparisons to other GPS data analyses are also presented for TEC,
indicating the influence of the PEC on the determination of latitudinal TEC
variations and also on the absolute TEC levels, by inducing an overestimate
of the receiver bias. The derived TEC latitudinal profiles, in comparison to
global map profiles, tend to differ from the map results only about as much
as the map results differ among themselves. A combination of ionosonde IEC
and alternative GPS TEC measurements, which in principle permits a PEC
determination through their difference, was compared to the composite and
separate ionosphere and plasmasphere contributions derived solely by the
SCORPION method for one station. Although there is considerably more scatter
in the PEC values derived from the difference of the GPS TEC and ionosonde
IEC measurements compared to the PEC values derived by the SCORPION method,
the average overhead values for this day are comparable for the two methods,
near 2 TEC units, at the South African site examined.<br><br>This initial investigation provides a basis for day-to-day TEC monitoring
for Africa, with separate ionosphere and plasmasphere electron content
determinations. |
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| ISSN: | 0992-7689 1432-0576 |