When the solar wind reaches the Earth's vicinity,and the Earth's dipole magnetic field,and the strength of the Earth's magnetic field lines going bending backward.However,the magnetic field pressure to block the movement of the plasma flow,making the solar wind can not be penetrated the Earth's atmosphere and magnetic field to move to circumvent the campaign.Thus forming a cavity,to be included on the magnetic field in the cavity,.At this time the size of a magnetic field to a large one small egg bar.
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