A stunning aurora borealis set to light up northern China

Solar activity is expected to be at moderate to high levels for the next three days from Friday, with a chance of M-class or larger solar flares, according to the forecast from the China Meteorological Administration's National Center for Space Weather.

Severe geomagnetic storms are expected due to coronal mass ejections (CMEs), and quiet to unsettled levels with possible active periods are expected on October 12 to 13. The ionosphere is expected to be disturbed on October 11 and October 12 due to the geomagnetic storm and will return to calm on October 13.

The China Meteorological Administration's National Center for Space Weather reminds aurora enthusiasts that, from the evening of October 10, especially from the early morning on the following day to the early morning of the October 12, there is a chance of observing relatively obvious auroras in northern China, with some regions even possibly seeing red and green composite auroras.

What is a geomagnetic storm?

As the most typical solar flare activity, one CME event can eject billions of tonnes of solar material from the solar surface at a speed of hundreds of kilometers per second. It not only carries a huge amount of kinetic energy due to its mass and speed, but also carries strong magnetic field energy. Once it hits Earth, it will cause changes in the direction and magnitude of the geomagnetic field, resulting in a geomagnetic storm.

Why have geomagnetic storms been occurring so frequently in recent years?

Just like the Earth's weather, space weather alternates between calm and active periods but with a longer cycle, typically 11 years. Since entering the 25th solar cycle in December 2019, solar activity has significantly intensified with frequent occurrences of X-class flares, solar proton events, and strong geomagnetic storms. The frequency and intensity are far exceeding those of the same period of the 24th cycle. Another reason is that, thanks to the advancements in China's space weather monitoring network in recent years, more accurate forecasts are now possible.

How are auroras generated?

Auroras are actually "by-products" of geomagnetic storms. When coronal mass ejections from the sun reach Earth, some of their energy enters the atmosphere near the poles, guided by the Earth's magnetic field. These charged particles collide with atmospheric atoms and molecules 100 to 400 kilometers above the ground. During these collisions, energy is transferred to the outer electrons of the atmospheric particles. This energy then rapidly releases and creates the stunning light that we know as auroras. 

(Cover: Aurora on the horizon over waters of Lake Ellesmere, Christchurch, New Zealand, May 11, 2024. /CFP)