Regional character of induced magnetic variations in India |
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| Authors: | AK Agarwal BP Singh N Nityananda |
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| Institution: | Indian Institute of Geomagnetism, Colaba, Bombay 400 005, India |
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| Abstract: | Variations recorded simultaneously at eight Indian stations during a magnetic storm are analysed to obtain the power spectra for each component using the fast Fourier transform. For two selected peaks, observed for H at all stations, at 49.5- and 70-min periods, a complex demodulation is performed for each component. From the variations thus obtained, horizontal polarization ellipses are drawn for four events of 49.5-min period. The variation of the demodulates and polarization ellipses at the stations shows a regional character which coincides with the physiographic grouping of the stations. Anomalously large Z variations are observed at the equatorial stations, which are near the sea. A distinct feature is the suppression of H at Trivandrum where the polarization ellipses confirm the E-W trend of the induced currents in this region. The overall similarity of the horizontal variations is demonstrated by these ellipses. Horizontal disturbance vectors at Annamalainagar, Trivandrum and Sabhawala confirm channelled currents located previously. At Shillong, the induced effects are evident and the currents are deduced to flow eastward, directly beneath the station.The overall regional similarities in variations are clearly manifested. |
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