NASA's Solar Dynamics Observatory (SDO) has observed a massive coronal hole on the Sun, spanning approximately 800,000 kilometers in diameter. This structure is releasing a stream of solar wind that is expected to reach Earth on January 31st, potentially causing a minor G1-class geomagnetic storm.
Coronal holes are regions on the Sun where the magnetic field is open to interplanetary space, allowing solar material to be ejected at high speeds. Unlike sunspots, which are closed by strong magnetic fields, these dark zones allow heat and charged particles to escape freely into space. These events often lead to solar or geomagnetic storms when the solar wind reaches Earth, but the effects are weaker compared to those caused by coronal mass ejections (CMEs).
Due to their open magnetic structure, coronal holes are cooler than surrounding areas and appear as dark spots in telescope images. The recent massive hole on the Sun was captured by NASA's SDO, which has been monitoring the dynamics of our star for over 15 years. It is equipped with instruments such as the Extreme Ultraviolet Variability Experiment, which measures ultraviolet radiation, and the Helioseismic and Magnetic Imager, which analyzes magnetic activity.
The solar wind emanating from this coronal hole is traveling at a speed exceeding 500 kilometers per second, meaning it will impact Earth's magnetosphere within a few days. While this stream of charged particles is expected to cause only a minor G1-class geomagnetic storm, stronger events like those associated with CMEs can have serious consequences, including satellite malfunctions and problems with power grids.
The Sun is currently at the peak of its 11-year cycle of activity, indicating that more powerful geomagnetic storms are expected throughout 2025. Such events can produce spectacular displays of auroras, even in southern parts of Europe. However, despite increased solar activity, the Sun briefly lost its sunspots on January 27th.