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Secular Variation

Rapid decrease in total geomagnetic field intensity F at and around Maitri:

 

The total intensity F measured at DG and later at Maitri show a decrease of more than 1000 nT from 1982-1996. Further examination of the F values from IGRF suggests a drop of ~120 nT/yr at the geographic location of Maitri. A decrease of nearly 17% was observed since 1922, which is a considerable magnitude within 75 years. Examinations of F data from other northern and southern stations suggest that this decrease is occurring only in southern hemisphere. Further analysis of magnetic data from high-latitude stations in northern and southern hemisphere indicate that this rapid decline is confined to a narrow horse shoe shaped belt in the Antarctic region, encompassing Maitri. The rate of decline falls as one moves away in the poleward and equatorward directions.

 

Change of Earth Magnetic field at Alibag & Maitri (left panel), Rate of Change of magnetic field in southern hemisphere (middle panel) and change of magnetic field at mid latitude location in northern hemisphere (right panel). The rate of decrease has reduced since 2006 and is now ~70nT/yr.



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