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Our Sun is a dynamic star, constantly bombarding our planet with charged particles that cause aurorae and geomagnetic storms. Now, a team of researchers found that an energetic outburst by our star disrupted our planet’s magnetic field for two hours in 2023.
The event occurred on April 24, 2023, when a coronal mass ejection (CME)—a burst of solar radiation from the Sun—swept over our planet. CMEs are generally faster than the Alfvén speed, or the speed of magnetic field lines through plasma.
But that wasn’t the case in late April of last year, when NASA’s Magnetospheric Multiscale mission observed an Alfvén speed faster than the CME that swept towards our planet. The mission detected electron and ion energy fluxes, and changes in electron density, as the solar event passed through. The CME caused Earth’s bow shock—the shockwave that typically forms when a CME hits Earth’s magnetic field—to disappear for two hours, from approximately 8:30 a.m. to 10:30 a.m. ET. The team’s analysis of the surprising solar event was published last week in Geophysical Research Letters.
“The terrestrial bow shock disappears, leaving the magnetosphere exposed directly to the cold CME plasma and the strong magnetic field from the Sun’s corona,” the study authors wrote in the paper. “Our results show that the magnetosphere transforms from its typical windsock-like configuration to having wings that magnetically connect our planet to the Sun.”
These structures—called Alfvén wings—acted as a highway transporting plasma between the Sun and Earth’s magnetosphere, according to an American Geophysical Union release. The team noted that Alfvén wing aurorae could occur on Earth, and could be observed in future studies.
“The wings are highways for Earth’s plasma to be lost to the Sun, and for the plasma from the foot points of the Sun’s erupted flux rope to access Earth’s ionosphere,” the team added. “Our work indicates highly dynamic generation and interaction of the wing filaments, shedding new light on how sub-Alfvénic plasma wind may impact astrophysical bodies in our solar and other stellar systems.”
CMEs should not be confused with solar flares, the brilliant events that can cause geomagnetic storms on Earth. As explained by EarthSky, both solar flares and CMEs are caused by realignments of the Sun’s magnetic fields, pushing energy out into space. Solar flares are bright flashes on the Sun’s surface, but CMEs launch magnetized particles into space, sometimes in Earth’s direction.
The team added that “Sun-Earth connection through Alfvén wings is analogous to the Jupiter-Ganymede connection,” indicating that aurorae on Jupiter’s moon Ganymede may be forged by similar Alfvén wing pathways.
More observations could reveal how the Sun’s powerful outbursts affects other heavenly bodies in our cosmic neighborhood. But as far as Earth’s magnetic field is concerned, everything is back to normal…for now!
