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Seasonal Crack in Earth’s Magnetic Field

It might sound like science fiction but it is not. Earth is surrounded by a magnetic force-field, a bubble in space called “the magnetosphere” which is tens of thousands of miles wide. On March 16-17, 2019, a magnetic crack opened for more than 5 hours, creating a geomagnetic storm that sparked stunning auroras around the Arctic Circle.

Although the exact date of the storm was not predicted, it comes as no surprise, because March is the most geomagnetically active month of the year. With the vernal equinox only days away, and at this time of year, cracks often form in the Earth’s magnetic field. It is the solar wind, pouring through the gaps, that fuels the phenomena creating bright displays of Arctic lights.

This amazing sight is called the “Russell-McPherron effect,” named after the researchers who first explained it. Scientists have been aware of this phenomenon for decades. It is basically described this way: the geometry of the solar wind and our magnetic field around the time of the equinoxes is such that the two opposing fields cancel each other out, opening up weaknesses or “cracks” in our magnetosphere.

Our magnetic shield is drafty, like a house with a window stuck open during a storm. The house deflects most of the storm, but the furniture is ruined. Similarly, our magnetic shield takes the brunt of space storms, but some energy slips through its cracks, sometimes enough to cause problems with satellites, radio communication, and power systems.

Fortunately, these cracks do not expose Earth’s surface to the solar wind. Our atmosphere protects us, even when our magnetic field doesn’t. The effects of solar storms are felt mainly in the high upper atmosphere and the region of space around Earth where satellites orbit.


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