CHANCE OF STORMS ON MEMORIAL DAY: NOAA forecasters estimate a 55% chance of G1-class geomagnetic storms on May 30th when Earth enters a high-speed stream solar wind flowing from this coronal hole:
Coronal holes are places in the sun’s atmosphere where the magnetic field opens up and allows solar wind to escape. When solar wind leaves the sun, it carries some of the sun’s magnetic field with it to Earth. This is key: Magnetic fields in the emerging stream have a negative polarity (“negative Bz”). Such fields can pry open a crack in Earth’s magnetosphere, allowing solar wind to pour in and fuel geomagnetic storms. High-latitude sky watchers should therefore be alert for auroras on May 30th, especially in the southern hemisphere where darkening autumn skies favor visibility of faint lights.