Abstract

Employing an array of three low latitude stations situated in India at Hanley (HAN) (L=1.178 R_E), Nagpur (NAG) (L=0.974 R_E) and Pondicherry (PON) (L=0.910 R_E ), a recent study has been carried out for Ultra Low Frequency (ULF) Magneto-hydrodynamic (MHD) waves in the 6.7 to 22.2 mHz frequency range, designated as Pc4 Magnetic Pulsations. These are observed mainly in the dayside (0400-2000 hrs LT) magnetosphere. The present research has been undertaken for describing the dependence of low latitude Pc4 occurrence (with time resolution of 1 minute) on the Solar Wind Velocity (V_SW) (hourly data) and the Interplanetary Magnetic Field (IMF) (hourly data) for the period range 01 January to 31 December, 2005. The mean measured frequency ranges of occurrence for HAN, NAG and PON were determined as 12.9 to 14.6 mHz, 12.7 to 14.2 mHz and 12.0 to 15.0 mHz respectively. The results for the whole year 2005 provided similar patterns of Pc4 occurrence for V_SW at all the three stations. Although Pc4 occurrence was reported for V_SW ranging from 250 to 1000 km/s, yet the major Pc4 events occurred for a V_SW range of 300-700 km/sec. Even though at all the three stations, the IMF magnitude spread up to 22 nT, yet the majority of Pc4 events occurred for a narrower range of 2-10 nT. However, it is important to note that the peak in the Pc4 occurrence was observed for IMF range of 3 to 6 nT. The implications of these results are reported in this study.