Abstract:
The aim of the present study is to investigate the response of ionospheric total electron content (TEC),
Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) scintillations
during 17 March 2015 St. Patrick’s Day geomagnetic storm over Visakhapatnam, which is popularly
known as Waltair (WALT) in the literature. GPS TEC observations obtained from five IGS stations
(SGOC, IISC, HYDE, LCK4 and LHAZ) and WALT during the storm have been compared. The TEC
derived from GPS, GLONASS constellations and CODE global ionosphere TEC map (GIM) over WALT
has also been compared. Positive storm effect during the main phase of the storm and negative storm effect
during the recovery phase of the storm were observed over the said stations. The variation of northern
equatorial ionisation anomaly TEC (CODE GIM TEC maps) in response to the St. Patrick’s Day storm
over four Indian longitudes (75◦E, 80◦E, 85◦E and 90◦E) has also been presented. Strong amplitude
and phase scintillations were observed in the L-band signals of GPS and GLONASS constellations over
WALT. Twelve satellite (Pseudo Random Noise) PRNs of GPS L1 and nine PRNs of each GLONASS
L1 and L2-band signals were affected by strong amplitude and phase scintillation. The peak amplitude
scintillation index (S4) obtained from the effected PRNs of GPS L1 signal and GLONASS L1-band
signals over WALT range from 0.36 to 0.74 and 0.36 to 0.76, respectively. Strong fluctuations in rate of
TEC index are noted over the said stations. This enhanced scintillation activity is mainly due to the
main phase of the storm falls in the evening sector over the Indian region.
