A huge butterfly-shaped crown hole opens in the sun's atmosphere and is currently emitting fast-moving solar winds toward the earth, which could trigger a mild geomagnetic storm and dazzling aurora this weekend.
High-speed solar wind spanning about 310,000 miles (500,000 kilometers) is expected to reach Earth around September 14.
Space weather forecasts are expected to be active on G1 (secondary) geomagnetic storm conditions and may reach G2 (medium) geomagnetic storm levels between September 13 and 14, according to the UK Metropolitan Office. NOAA's Space Weather Forecasting Center has released a more cautious estimate that only peaks in the G1 condition are expected. However, if the embedded magnetic field lines of the solar wind are favorable to the embedded magnetic field lines of the earth, they have the potential to be more active.
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Geomagnetic storms are classified using G-level, which the G-scale ranks from G1 (secondary) to G5 (extreme). A halo occurs when the solar wind interacts with the Earth's magnetic field. Charged particles from the sun collide with gases, such as oxygen and nitrogen, in the upper atmosphere, transferring energy to them. This energy is released in light, creating a colorful display seen in the night sky. The stronger the solar wind, the more vibrant and wider the aura becomes.
NOAA's WSA-Enlil solar wind model shows predicted plasma density (top) and radial velocity (bottom) throughout the solar system. The sun is in the center (yellow), the earth is green, and the stereo A is red. These predictions help track solar wind flow and potential CME effects. (Photo source: NOAA Space Weather Forecasting Center)
Russell-McPherron effect
For Aurora Hunters, this weekend’s storm watch is particularly effective during the year. During the spring and autumn equinoxes, the Earth's direction in space makes the planet's magnetic field easier to connect with the interstellar magnetic field carried by the solar wind. This seasonal elevation to geomagnetic activity is known as the Russell-McPherron effect, which was first described in 1973 by geophysicists Christopher Russell and Robert McPherron.
During the vernal equinox, the sun shines directly on the Earth's equator, making the day and night equal to the two hemispheres. Meanwhile, the magnetic poles of the earth are aligned in such a way that the incoming solar wind flow can be more efficiently connected to the magnetic layer. For most of the year, the tilt of the Earth causes the Earth's magnetic field and the Sun to slightly misalign, which helps deflect some of the incoming charged particles. But around the vernal equinox, the natural buffer is weakened. As a result, space weather disturbances, such as coronal holes or coronal mass ejections (CMEs), can provide stronger impact.
Long-term research shows that during the vernal equinox, geomagnetic storms are about twice as likely to be around dissolving in June and December. With the emergence of fall on September 22, even moderate solar wind conditions will produce brighter and wider aurora than before.
During the period 1930-2007, the average number of geomagnetic interference days per month. Geomagnetic activity appears to peak in the spring and fall months. (Image source: NASA/MSFC -David Hathaway.)
If a G2 storm does occur this weekend, auroras can be seen in the central to the highest patches throughout the northern hemisphere, including Canada, Alaska, Alaska, Scandinavia and the southern hemisphere in the northern United Kingdom, Auroras may light up the sky over the Antarctic sky with less visibility in Tesmania and South Zealand.
As always, in space weather, predictions come with uncertainty, and the aurora may become varied. The real advantage of this weekend’s storm depends on the exact conditions when the solar wind reaches Earth. Nevertheless, with the butterfly-shaped crown hole exploding, the vernal equinox effect promotes the odds of the aurora, and you may still want to keep your eyes and camera in the sky.