Near-Conjugate Characteristics of Long Period ULF waves at very high Latitudes (L≈14 RE)

Abstract:

Indian Antarctic station Bharati (CGM location 74.8 deg S, 97.8 deg E; L=14.8 R_E) and IMAGE chain observatory Hornsund (74.3 deg N, 108.5 deg E; L=14 R_E) form a near-conjugate pair. Around the latitudes of stations under consideration, the geomagnetic field lines are typically connected to the outermost region of magnetosphere. Using magnetic field variations recorded at these stations, we examine characteristics of the Pc5 band (frequency ~2-10 mHz) ULF activity. We observe that Pc5 activity, in general, maximizes near magnetic noon in both the hemispheres. Its amplitude appears related with the speed of the solar wind. For the selected events when the footprints of CLUSTER satellites were close to the ground stations, strikingly similar waveforms were observed on the ground and in the magnetosphere. Possible cause for generation of Pc5 waves at very high latitudes and the ionospheric modulation have been discussed.