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  3. Periodic realignment of the Earth’s magnetic field occurs two ways: t

Periodic realignment of the Earth’s magnetic field occurs two ways: t

游客2024-01-11  30
问题            Periodic realignment of the Earth’s magnetic field occurs two ways: the
       first, "field regeneration", or the creation of new magnetic fields from the
       ambient geomagnetic field, takes place because magnetic field lines are trapped
Line    in effective electrical conductors. The field is trapped in molten iron which
(5)      moves in response to the forces imposed upon it and as the core moves, the field
       lines are stretched and twisted, creating a new magnetic field. The second
       process is the diffusion of the magnetic fields: in the same way that a drop of
       dye will soon diffuse throughout a swimming pool, a concentration of magnetic
       field lines diffuses throughout the planet’s outer core. On the large scale of
(10)     stars and planets, the field lines are caught up in the fluid motion and distorted,
       generating a new magnetic field before diffusing away. This rarer type of field
       reversal is likely caused by unexplained larger changes in the flow in the outer
       core, though scientists have suggested such fluctuations may simply be extreme
       examples of fluctuations in the dynamo processes-an El Nino in the weather of
(15)     the outer core. [br] Which of the hypothetical discoveries would MOST likely shed doubt on the author’s claim that "field regeneration" could be responsible for the earth’s magnetic reversals?
选项 A、Extreme fluctuations in the dynamo processes are discovered to be exceedingly rare, if they occur at all.
B、Magnetic field lines are discovered to diffuse very poorly through the earth’s outer core.
C、Realignment of the earth’s magnetic polarity is discovered to occur much more frequently than was previously believed.
D、Molten iron is discovered to be a poorer electrical conductor than was previously believed.
E、The earth’s core is found to move at a much faster rate than had previously been measured.
答案 D
解析
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