Geophysics, Lecture Notes- Physics - Prof Gavin Bell 16

Geophysics, Lecture Notes- Physics - Prof Gavin Bell 16 -...

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PX266 Geophysics (2010/11) Lecture 15 Handout – Earth’s Magnetic Field and Paleomagnetism Dr. Gavin Bell Magnetic declination: angle between magnetic and geographical meridians. Magnetic inclination: angle I at which local field dips below horizontal, depending only on latitude for a cylindrically symmetric (dipole) field. tan 2 tan I Where are the geomagnetic poles (GMPs) right now? NGMP: Canadian Arctic, 82°N 248°E. SGMP: Antarctic Ocean, 65°S 138°E. These are not antipodal (i.e. opposite each other)! They also drift (see animation on course web site). The Earth’s field is quite close to but not precisely a dipole field – there are higher order components which alter the detailed form of the field, including breaking its N-S and longitudinal symmetry. Actually, symmetry-breaking is required in the “alpha-omega” theory of the self-exciting geodynamo. The non-dipolar components vary rapidly (timescale < 100 years). Changes in the geomagnetic field intensity and magnetic pole locations are known as
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This note was uploaded on 09/12/2011 for the course ECON 102 taught by Professor Gavinbell during the Spring '11 term at LSE.

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Geophysics, Lecture Notes- Physics - Prof Gavin Bell 16 -...

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