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WeatherWise: the equinox and the aurora

Posted at 6:54 PM, Mar 08, 2021
and last updated 2021-03-08 20:54:00-05

HELENA — Spring is almost here and so may be the northern lights.

It is not just a coincidence that these two beautiful phenomena have a relationship.

March is a great time to hunt for the aurora borealis, not because the lights are a fan of the new season.

The weeks around both the vernal (spring) equinox as well as the autumnal equinox tend to deliver enhanced geomagnetic activity in our atmosphere mainly because of the position of the earth.

It's really all about geometry.

At the equinoxes, the earth's two magnetized poles are at a right angle to the solar wind flow. Charged particles are more likely to be accelerated around the poles at this time and position. On the winter and summer solstice, the earth is tilted at 23.5 degrees, and solar winds are not as easily "caught" by the magnetic poles.

The aurora is caused by solar activity, but the sun does not know or care what season it is on earth. But when the earth is upright, there is a direct connection from the upper atmosphere to the sun making the geomagnetic disturbances almost twice as likely in spring and fall than winter and summer.

Timing is everything, and position helps too. While the northern lights are still dependent on solar activity, which is increasing, the next few weeks could offer some fire in the night sky. And now you're a little more weather-wise.