Dependence of solar wind velocity and interplanetary magnetic field on Pc4 magnetic pulsations at low latitudes in India

I. A. Ansari1*, K. A. Nafees1, A. K. Sinha2 and B. M. Pathan2
1Department of Physics, Aligarh Muslim University, Aligarh (U.P.) 202002, India
2Indian Institute of Geomagnetism, New Panvel(W), Navi Mumbai 410218, India

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Employing an array of three low latitude stations situated in India at Hanley (HAN) (L=1.178 RE), Nagpur (NAG) (L=0.974 RE) and Pondicherry (PON) (L=0.910 RE ), 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 (VSW) (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 VSW at all the three stations. Although Pc4 occurrence was reported for VSW ranging from 250 to 1000 km/s, yet the major Pc4 events occurred for a VSW 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.

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Keywords : Pc4 Magnetic pulsations– MHD waves and instabilities-solar wind–IMF control of Pc4 pulsations