I. A. Ansari *
Department of Physics, Aligarh Muslim University, Aligarh 202002, India
Abstract. Pc3 geomagnetic pulsations are quasi-sinusoidal variations in the earths magnetic field in the period range 10-45 seconds. These pulsations can be observed in a number of ways. However the application of ground based magnetometer arrays has proven to be one of the most successful methods of studying the spatial structure of hydromagnetic waves in the earth's magne- tosphere. The solar wind provides the energy for the earth's magnetospheric processes. Pc3-5 geomagnetic pulsations can be generated either externally or internally with respect to the magnetosphere. The spatial and temporal varia- tions observed in Pc3 occurrence are of vital importance because they provide evidence which can be directly related to wave generation mechanisms both in- side and external to the magnetosphere. At low latitudes (L < 3) wave energy predominates in the Pc3 band and the spatial characteristics of these pulsations have received little attention in the past. An array of four low latitude induction coil magnetometers was established in south-east Australia over a longitudinal range of 17 degrees at L=1.8 to 2.7 for carrying out the study of the effect of the solar wind velocity on these pulsations. Digital dynamic spectra showing Pc3 pulsation activity over a period of about six months have been used to evaluate Pc3 pulsation occurrence. Pc3 occurrence probability at low latitudes has been found to be dominant for the solar wind velocity in the range 320- 700 Km s-1 . The results suggest that solar wind controls Pc3 occurrence through a mechanism in which Pc3 wave energy is convected through the magnetosheath and coupled to the standing oscillations of magnetospheric field lines.
Keywords: Pc3 magnetic pulsations - Pc3 occurrence - solar wind velocity magnetospheric physics