A solar wind disturbance deprived Earth of its magnetic tail

Aug. 2 () –

Data collected by a NASA space mission have yielded unprecedented observations of a rare phenomenon created during a solar coronal mass ejection (CME).

Like a supersonic jet powered by high-speed winds, Earth is constantly bombarded by a stream of charged particles from the Sun known as the solar wind.

Much like the wind around an airplane or the water around a ship, these streams of solar wind curve around the Earth’s magnetic field, or magnetosphere, forming a front called a bow shock on the side of the magnetosphere facing the sun. and stretching it out into a windsock with a long tail on the night side.

Dramatic changes in the solar wind alter the structure and dynamics of the magnetosphere. An example of such changes provides insight into the behavior of other bodies in space, such as Jupiter’s moons and extrasolar planets.

CMEs typically travel faster than the Alfvén velocity, the speed at which vibrating magnetic field lines move through magnetized plasma, which can vary with the plasma’s environment. In 2023, a CME disrupted the normal configuration of Earth’s magnetosphere for about two hours.

Researchers led by Li-jen Chen of NASA’s Goddard Space Center analyzed observations from NASA’s Magnetospheric Multiscale Mission (MMS) to find out what happened. Results published in Geophysical Research Letters.

On April 24, 2023, the MMS mission observed that although the solar wind streaming velocity was fast, the Alfvén velocity during the strong CME was even higher. Normally, the solar wind travels faster than the Alfvén velocity. This anomaly caused the Earth’s shock wave to temporarily disappear.which allowed the Sun’s plasma and magnetic field to interact directly with the magnetosphere.

The tail of Earth’s windsock was replaced by structures called Alfvén wings. that connected the Earth’s magnetosphere to the recently erupted region of the Sun. This connection acted as a highway transporting plasma between the magnetosphere and the Sun.

The unique CME event offered new insights into how Alfvén wings form and evolve, the authors write. A similar process could occur around other magnetically active bodies in our solar system and the universe, and the researchers’ observations suggest that aurora formation on Jupiter’s moon Ganymede may also be attributed to Alfvén wings. The authors suggest that future work one could look for similar Alfvén wing auroras on Earth.