 |
| Titel |
Temporal and spatial variations in TEC using simultaneous measurements from the Indian GPS network of receivers during the low solar activity period of 2004-2005 |
| VerfasserIn |
P. V. S. Rama Rao, S. Gopi Krishna, K. Niranjan, D. S. V. V. D. Prasad |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 24, no. 12 ; Nr. 24, no. 12 (2006-12-21), S.3279-3292 |
| Datensatznummer |
250015704
|
| Publikation (Nr.) |
 copernicus.org/angeo-24-3279-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
With the recent increase in the satellite-based navigation applications, the
ionospheric total electron content (TEC) and the L-band scintillation
measurements have gained significant importance. In this paper we present
the temporal and spatial variations in TEC derived from the simultaneous and
continuous measurements made, for the first time, using the Indian GPS
network of 18 receivers located from the equator to the northern crest of
the equatorial ionization anomaly (EIA) region and beyond, covering a
geomagnetic latitude range of 1° S to 24° N, using a 16-month period
of data for the low sunspot activity (LSSA) years of March 2004 to June 2005.
The diurnal variation in TEC at the EIA region shows its steep increase and
reaches its maximum value between 13:00 and 16:00 LT, while at the
equator the peak is broad and occurs around 16:00 LT. A short-lived day
minimum occurs between 05:00 to 06:00 LT at all the stations from
the equator to the EIA crest region. Beyond the crest region the day maximum
values decrease with the increase in latitude, while the day minimum in TEC
is flat during most of the nighttime hours, i.e. from 22:00 to 06:00 LT,
a feature similar to that observed in the mid-latitudes. Further, the
diurnal variation in TEC show a minimum to maximum variation of about 5 to
50 TEC units, respectively, at the equator and about 5 to 90 TEC units at the
EIA crest region, which correspond to range delay variations of about 1 to 8 m
at the equator to about 1 to 15 m at the crest region, at the
GPS L1 frequency of 1.575 GHz. The day-to-day variability is also
significant at all the stations, particularly during the daytime hours, with
maximum variations at the EIA crest regions. Further, similar variations are
also noticed in the corresponding equatorial electrojet (EEJ) strength, which
is known to be one of the major contributors for the observed day-to-day
variability in TEC.
The seasonal variation in TEC maximizes during the equinox months followed by
winter and is minimum during the summer months, a feature similar to that
observed in the integrated equatorial electrojet (IEEJ) strength for the
corresponding seasons. In the Indian sector, the EIA crest is found to occur
in the latitude zone of 15° to 25° N geographic latitudes (5° to
15° N geomagnetic latitudes). The EIA also maximizes during equinoxes
followed by winter and is not significant in the summer months in the LSSA
period, 2004–2005. These studies also reveal that both the location of the
EIA crest and its peak value in TEC are linearly related to the IEEJ
strength and increase with the increase in IEEJ. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|