http://www.spaceweather.com/ GEOMAGNETIC STORM, SUBSIDING: Earth's magnetic field is calming down on June 1st following nearly 15 hours of non-stop geomagnetic storming. The storminess was caused by the arrival of an interplanetary shock wave on May 31st (1618 UT). The source of the shock is unknown. Current speculation focuses on a corotating interaction region (CIR)--that is, a shock-like transition zone between high- and low-speed solar wind streams.
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