Low latitude Pc1 pulsation as observed from ground-based search coil magnetometer

Magnetic data from searchcoil magnetometer in the Indian sector have been analyzed to study geomagnetic pulsations in the near equator low latitude region (geomag. lat.< 20 degrees). Apart from normal Pc4 pulsations (which is expected at such location), we observe the presence of Pc1 oscillations (frequency similar to 4 Hz) which are very unlikely at these latitudes. The interesting aspect of these observed pulsations is that they follow a broad-band spike during post-sunset and pre-dawn hours, whereas during day time the absence of broad band spike and simultaneous enhancement in the power of Schumann resonance was observed. Observations suggest that these two types of Pc1 pulses are sustained by different energy sources.