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Solar Magnetic Crochet

  1. Mar 30, 2014 #1


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    When I linked to this morning's spaceweather.com, I read the following, which appears to be a notable disturbance of Earth's magnetic field simultaneous to a strong flare on the sun. Normally it's said to take hours or days for the effects of a flare to be felt on Earth, but in this case there was no such delay. How does it work so quickly?

    SOLAR FLARE CAUSES RARE 'MAGNETIC CROCHET': On March 29th at 17:52 UT, the magnetic canopy of sunspot AR1890 erupted, producing a brief but intense X1-class solar flare. NASA's Solar Dynamics Observatory recorded the extreme ultraviolet flash:

    Radiation from the flare caused a surge in the ionization of Earth's upper atmosphere--and this led to a rare magnetic crochet, measuring 17 nT at the magnetometer in Boulder, Colorado.

    A magnetic crochet is a ripple in Earth's magnetic field caused by electrical currents flowing in air 60 km to 100 km above our heads. Unlike geomagnetic disturbances that arrive with CMEs days after a flare, a magnetic crochet occurs while the flare is in progress. They tend to occur during fast impulsive flares like this one.
  2. jcsd
  3. Mar 31, 2014 #2
    The crochet is caused by ionization in the atmosphere by x-rays emitted by the solar flare. These move at the speed of light. See the last link you posted.
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