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| Titel |
On the validity of the ionospheric pierce point (IPP) altitude of 350 km in the Indian equatorial and low-latitude sector |
| VerfasserIn |
P. V. S. Rama Rao, K. Niranjan, D. S. V. V. D. Prasad, S. Gopi Krishna, G. Uma |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 24, no. 8 ; Nr. 24, no. 8 (2006-09-13), S.2159-2168 |
| Datensatznummer |
250015617
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| Publikation (Nr.) |
 copernicus.org/angeo-24-2159-2006.pdf |
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| Zusammenfassung |
| The GPS data provides an effective way to estimate the total electron
content (TEC) from the differential time delay of L1 and L2 transmissions
from the GPS. The spacing of the constellation of GPS satellites in orbits are
such that a minimum of four GPS satellites are observed at any given point
in time from any location on the ground. Since these satellites are in
different parts of the sky and the electron content in the ionosphere varies
both spatially and temporally, the ionospheric pierce point (IPP) altitude
or the assumed altitude of the centroid of mass of the ionosphere plays an
important role in converting the vertical TEC from the measured slant TEC
and vice versa. In this paper efforts are made to examine the validity of
the IPP altitude of 350 km in the Indian zone comprising of the
ever-changing and dynamic ionosphere from the equator to the ionization anomaly
crest region and beyond, using the simultaneous ionosonde data from four
different locations in India. From this data it is found that the peak
electron density height (hpF2) varies from about 275 to 575 km at
the equatorial region, and varies marginally from 300 to 350 km at and
beyond the anomaly crest regions. Determination of the effective altitude of
the IPP employing the inverse method suggested by Birch et al. (2002) did
not yield any consistent altitude in particular for low elevation angles, but
varied from a few hundred to one thousand kilometers and beyond in the Indian
region. However, the vertical TEC computed from the measured GPS slant TEC
for different IPP altitudes ranging from 250 to 750 km in the Indian region
has revealed that the TEC does not change significantly with the IPP
altitude, as long as the elevation angle of the satellite is greater than 50
degrees. However, in the case of satellites with lower elevation angles
(<50°), there is a significant departure in the TEC computed using
different IPP altitudes from both methods. Therefore, the IPP altitude
of 350 km may be taken as valid even in the Indian sector but only in the
cases of satellite passes with elevation angles greater than 50°. |
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