A large coronal hole in the Sun’s atmosphere is currently in front of Earth, sending a burst of high-speed solar wind our way that could trigger geomagnetic storms and auroras this weekend.
fasting solar wind The stream is expected to arrive late Saturday into Sunday (Oct. 11-12), according to both space weather forecasters. NOAA Space Weather Prediction Center and the United Kingdom Meteorological Office. Geomagnetic activity could begin to recover at the end of October 11, with the increased activity scheduled for between 5 am and 5 pm EDT (0900-1700 GMT) on October 12.
If predicted minor geomagnetic storm (G1) conditions are reached on October 12, auroras could be visible as far north as Michigan and Maine, according to NOAA G Scalethat qualifies the strength of these disturbances. But given the time of year, just after the recent autumn equinoxEven a small increase in activity could have a larger impact and increase the chances of a more widespread expansion. auroras this weekend.
This isn’t the first time we’ve seen this particular coronal hole, although it looks a little different. It is the same characteristic that we saw last monthwhich took the form of a butterfly or a bird. Coronal holes can persist for months and reappear every 27 days or so as the sun completes a solar rotation.
Coronal holes are areas where the sun’s magnetic field opens up, allowing the solar wind to flow more freely into space. When this solar wind reaches Earth, it interacts with us planet’s magnetic fieldor magnetosphere, and some of those energetic particles are guided by magnetic field lines toward the poles. When they collide with atoms and molecules high in Earth’s atmosphere, primarily oxygen and nitrogen, they release energy in the form of light, creating the bright curtains we know as the aurora.
Seasonal ‘bump’ in the auroras
This weekend’s timing is good for aurora chasers, as around the fall equinox, Earth’s tilt aligns in a way that helps the solar wind connect more efficiently with our planet’s magnetic field. This seasonal boost is known as the Russell-McPherron effect.
NOAA latest forecast predicts a maximum Kp index of 5, which corresponds to minor geomagnetic storm conditions (G1). The Kp index is a global scale that measures geomagnetic activity from 0 (calm) to 9 (extreme). The higher the number, the greater the chances of seeing auroras further from their usual polar regions.
Space weather forecast
For a full breakdown of what’s happening on the Sun and what to expect from space weather this weekend and next week, check out the latest forecast from space weather physicist Tamitha Skov:
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