- A stealth solar storm reached Earth on November 20 without warning signs
- Stealth CMEs are faint, slow solar eruptions that evade normal detection methods
- NOAA noted unusual solar wind changes suggesting a stealth CME impact on Earth
A solar storm quietly reached Earth on November 20, surprising scientists because it arrived without any warning signs. This type of eruption, called a stealth solar storm, is unusual because it cannot be easily seen in regular solar images. Even though this event did not trigger a geomagnetic storm, it may have helped create auroras visible in some mid-latitude regions, reported Space.com.
Stealth solar storms are coronal mass ejections (CMEs) that emerge from the Sun but leave almost no visible traces along their path. Normal CMEs are easily detected in solar observations, but stealth CMEs erupt extremely quietly and slowly, making them extremely challenging to track.
While normal CMEs appear as bright flares, sudden changes in ultraviolet light, or large loop-like formations rising from the Sun's surface, and coronagraphs capture them as large, diffuse clouds, stealth CMEs behave in the opposite way. They appear very faint, move slowly, and leave no bright signature behind. Because of this, scientists often detect them only when they approach Earth and disrupt the solar wind.
This is exactly what happened on November 20th. NOAA experts observed unusual changes in solar wind patterns and speculated that a stealth CME may have struck Earth. On that day, the solar wind was primarily influenced by a coronal hole's high-speed stream with negative polarity. They also recorded a signal called an "embedded transient," which is believed to be a hidden clue to a stealth CME.
The most significant signal was a sudden increase in the magnetic field. The solar wind speed was between 400-500 km/s, which is higher than the normal speed around Earth.
Space weather expert Tamitha Skov reported on social media that stealth solar storms have become active again. She said they are called "stealthy" because they leave no visible trace in observations of the Sun's disk or coronagraph. According to her, such storms are only detected when they collide with Earth.
They added that this event is likely to cause a mild geomagnetic storm at high latitudes. However, they also warned that when stealth CMEs pass near high-speed solar wind currents, they can in some cases produce more powerful storms than expected.
Stealth CMEs are typically more common when the Sun is in the waning phase of its 11-year solar activity cycle. During this time, the Sun's magnetic activity changes, increasing the likelihood of unusual events.
Although the November 20th storm did not pose a major threat, its nature is significant. It highlights how unpredictable the Sun can be and reminds us that even seemingly quiet eruptions can impact Earth's space environment.
