首页|Secular trend of geomagnetic elements in the Indian region
Secular trend of geomagnetic elements in the Indian region
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NSTL
Terra Scientific Publ Co
In the present study, secular trends and jerks in the geomagnetic elements D, H and Z are investigated at the six Indian magnetic observatories using annual and monthly mean values for all days, quiet days and night base (night time mean). The residuals of all-day annual and monthly means are computed by removing a polynomial fit from their best fitting curves. The residuals of D, H and Z curves do not show any parallelism with the 11-year sunspot cycle. At Alibag, the D residual shows a periodicity of 2 solar cycles, whereas the H and Z residuals indicate a quasi-periodicity of 3 solar cycles for the period 1921-2009. At the Indian stations, an in-phase solar cycle component is observed for 2 of the solar cycles in the D and Z residuals, while the H residual shows outof- phase variations with the sunspot cycle for the period 1958-2009. Two geomagnetic jerks, 1970 and 1991, are well reflected in the monthly and annual mean values in the Indian region, as observed globally.
Secular variationcore-mantlegeomagnetic jerkssolar cyclepolynomial fit
S. K. Bhardwaj、P. B. V. Subba Rao
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Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410 218, India
NSTL
Terra Scientific Publ Co
