The solar wind is a permanent feature of the Solar System, except for Christmas 2022, when it suddenly disappears completely. The strange phenomenon was detected by a NASA spacecraft orbiting Mars, and the red planet’s magnetosphere was found to have tripled in size in response.

Because the sun operates like a giant fusion reactor, it emits a constant stream of charged particles that we call the solar wind. This buffers entire planets and would strip them of their atmospheres were it not for a protective magnetosphere that deflects incoming particles.

The solar wind fluctuates, but it surprised astronomers when it suddenly stopped completely for several days last December. This anomaly was discovered by the NASA orbiter MAVEN, which surveyed the Martian atmosphere and whose instruments recorded a 100-fold decrease in the intensity of the solar wind. Without the pressure of the solar wind, the Red Planet’s magnetosphere and ionosphere have tripled. normal sizes.

“When we first saw the data and how dramatic the decline in solar wind was, it was almost unbelievable,” said the study’s lead author, Jasper Halekas. “We formed a working group to investigate the incident and found that this period was rich in incredible discoveries.”

MAVEN found that the ionosphere transitions from a magnetized state to a non-magnetized state, while the boundary region sees much less electromagnetic activity than normal. About two days later, the solar wind returned, providing the NASA team with a rare window into the unusual.

“We’re really seeing how Mars responds when the solar wind is effectively eliminated,” Halekas said. “It provides a great study of what Mars would be like if it orbited a less ‘windy’ star.”

The team says the drop is due to rare interaction between waves in the solar wind. A fast-moving wave catches up with a slower-moving wave, causing them to merge into a single wave, leaving behind a less dense region. This phenomenon is known to occur in very rare cases, including the event that destroyed the Earth in 1998, but there is generally no spacecraft that can study them as well as MAVEN.

The event occurred as a result of increased solar activity as the Sun approached the peak of its 11-year cycle. The study was presented at the fall meeting of the American Geophysical Union.