Banner
    What Is A Geomagnetic Storm?
    By News Staff | February 22nd 2011 04:46 PM | 3 comments | Print | E-mail | Track Comments
    Concerns about geomagnetic storms are all the rage this week, so what are they? A geomagnetic storm is a disturbance in the magnetosphere due to near-Earth space weather that happens when the interplanetary magnetic field turns southward and remains that way.

    Geomagnetic storms are associated with solar flares and coronal mass ejections (CME). The geomagnetic storm which happened last week had some effect on communications in China but obviously it could have been a lot worse. The recent geomagnetic storm was due to a Class X2.2 solar flare but in 1859 a real doozy happened, so powerful it knocked out telegraph wires and caused auroras so powerful at the poles people claimed they could read using the light. Since the sun is emerging from a relatively quiet period in its 11-year cycle we could see more severe geomagnetic storms as well.

    Southwest Research Institute defines a coronal mass ejection as a massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the solar corona and this one sent charged plasma particles toward Earth at about 560 miles per second.

    Some geomagnetic storms are recurrent and happen every 27 days, corresponding to the Sun's rotation period but others occur more frequently near solar maximum and have both the interplanetary shock wave and the CME that drives it.

    So what does it really mean to have a geomagnetic storm?   Basically, the magnetosphere is a region of space around Earth controlled by our planet's magnetic field and it forms a shield that normally protects Earth from solar wind storms.  A strong gust of solar wind can compress the magnetosphere and trigger a geomagnetic storm.


    This sequence shows a coronal mass ejection moving from the Sun after the onset of a solar flare on April 4, 2000. The solid colored circle in the middle is the occulting disk of the Solar and Heliospheric Observatory's C3 coronagraph. It blocks out the intense light of the Sun so that the tenuous corona is visible. The C3 coronagraph is able to observe the Sun's corona between 3.5 to 30 solar radii.  Credit: NASA

    As the material from a CME flows away from the Sun, it piles up against slower-moving gas that has been ejected earlier, which produces a sharp, dense shock front. The shock wave from the eruption on in the graphic above traveled two days through interplanetary space before reaching Earth. When it arrived it triggered aurora so bright that they could be seen from a brightly lit parking lot in Yonkers, New York.


    Simulation of a CME impact on Earth's magnetosphere. With the sun off screen to the left, the earth's magnetosphere is visualized as a series of translucent blue shells that depict the magnetic fields at 60, 75, and 85 degrees from the equator. The electrically charged CME travels through the magnetosphere in roughly one hour, compressing the magnetic field lines and inducing a buildup in the earth's auroras. After the CME passes, the field lines quickly return to their original configuration and the auroras return to their pre-impact energy levels. For visual clarity, this simulation shows the auroral increase peaking well after the CME passes.

    Comments

    Ironic that it starts with the prefix "-geo", considering that it is induced by the activity of the sun.

    Hank
    It's not irony since the storms occur on Earth.   We also call beach water low tide and high tide even though they are induced by the moon.
    how come nobody never talks about geomagnetic sun storms effect on sensitive people like I am. I get such bad misgraines during this 3 days that I want end my life. HTat how painfull it is. I end up in ER on March 10th 2011 on the same day an earthquake hit Japan.