| Autor: |
J.T. Weaver, A.K. Agarwal |
| Rok vydání: |
1990 |
| Předmět: |
|
| Zdroj: |
Physics of the Earth and Planetary Interiors. 60:1-17 |
| ISSN: |
0031-9201 |
| Popis: |
The induction effect on geomagnetic variations due to the daytime electrojet in the region of the Indian peninsula and Sri Lanka has been investigated numerically with the aid of a thin sheet algorithm. The electrojet is represented by a Gaussian current distribution over a band of about 600 km width with its maximum intensity close to the dip-equator and a height of 110 km. An inducing source comprising an equatorial electrojet superimposed on the uniform planetary field is also considered. The results are presented in the form of contour plots and the differences between the magnetic field components associated with electrojet and uniform sources are highlighted. It is observed that the non-uniformity of the source in daytime events has a profound effect on the induced currents in the region. The dual effect of reduced current intensity and opposing external and internal parts results in smaller vertical magnetic field variations over the southern peninsula especially close to the periphery of the electrojet. It is confirmed that for a pure electrojet source the vertical field vanishes completely in the region of the permanent geomagnetic station at Annamalainagar thereby lending credence to a recently proposed method of separating a daytime magnetic event into its ionospheric and magnetospheric parts. An examination of field ratios shows that the magnetotelluric impedance is less dependent on the source effect over the whole region than other parameters. Finally, it is shown that in the presence of a combined electrojet and uniform source field, the observed equatorial enhancement is not proportional to the strength of the electrojet alone but is also critically dependent on the intensity of the uniform part of the field. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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