Effects of SSC in geomagnetic field components H, D and Z at low-latitude stations during 1995–2001

•Variations in geomagnetic fields H, D and Z during quiet and storm periods were studied.•The geomagnetic storms with Dst<−100 nT were considered.•Equatorial regions of Indian subcontinent are studied.•The dependence of storm associated variations of H with Bz and IEF is estimated.

The present study is an analysis of the effects of storm sudden commencements (SSC) on geomagnetic field components H, D and Z during 1995–2001 with the data of five low-latitude stations in India, namely Pondicherry (PND, 2.85°N, 79.92°E), Visakhapatnam (VSK, 8.34°N, 83.32°E), Alibag (ABG, 10.19°N, 72.87°E), Nagpur (NGP, 12.12°N, 79.08°E) and Ujjain (UJJ, 14.43°N, 75.78°E). The characteristics of geomagnetic H, D and Z field components are studied under various geophysical conditions. For both quiet and storm times, the maximum amplitude of H is obtained at PND and it decreases with increase in latitude for the period 1995–2001.The amplitude of D component is larger at VSK and smaller at UJJ for both quiet and storm periods during 1995–2001. It is clear that the storm time Hmin values show no variation with solar activity at 2.85°N (PND). However, all the other latitudes in the present study such as at 8.34°N, 10.19°N, 12.12°N and 14.43°N, storm time Hmin values decrease with increase of S10.7. The values of ΔHmin shows positive correlations with solar activity, for the stations PND, VSK, ABG, NGP and UJJ, considered in the present study. The value of correlation coefficient obtained between H and interplanetary magnetic field and H and interplanetary electric field increases with increase of solar activity. The values of ΔHmin (ΔHmin=Hstorm−Hquiet) increase with increase of solar activity and correlate well with Dstmax for the five low-latitudes studied here.