A lucky spacecraft alignment has recorded a huge, developing solar explosion


Our Sun is not a cool ball scorching hot plasma. In fact, it explodes in a somewhat continuous mass explosion; Such coronal mass ejections are the cause of geomagnetic storms when directed to Earth.

From near-Earth space, we can measure them very well with satellites and other spacecraft. But something incredibly happened in 1998. Not only was a spacecraft near Earth able to measure a coronal mass ejection (CME), another spacecraft outside Mars lined up just the right way to receive a solar explosion.

This means that two spacecraft were able to measure the same CME at different points of their journey from the Sun, providing a rare opportunity to understand how these powerful explosions develop.

Coronal mass ejections may not appear as solar flares (which they sometimes accompany), but they are much more powerful. They occur when twisted magnetic field lines on the sun reconnect, convert and release tremendous amounts of energy in the process.

It occurs in the form of a CME, in which large amounts of ionized plasma and electromagnetic radiation, bound in a helical magnetic field, are launched into space in the solar wind. When they come to the rear of the Earth, CMEs can interact with the magnetosphere and the ionosphere, causing satellite communication problems and aurora-like effects.

But what happens to CMEs when they are out of the previous Earth, in interplanetary space, has become much more difficult to study. We have far, far fewer means for one thing. The difference of the spacecraft at two different distances from the Sun detecting the same CME is incredibly small.

Fortunately, the same happened in 1998 with two spacecraft designed to study solar space. NASA’s wind spacecraft, in a L1 Lagrangian point at about 1 astronomical unit (the distance between Earth and the Sun), first observed a CME on 4 March 1998.

Eighteen days later, the same CME arrived in Ulysses, a spacecraft that at the time was 5.4 astronomical units, equal to or less than Jupiter’s average orbital distance.

Now astronomers examined the data from both of those encounters to see how the CME changes when they travel deep into the solar system for the first time. In particular, he studied the magnetohydrodynamic evolution of the embedded magnetic cloud.

Wind data (left) and Ulysses data (right). (Teloni et al., APJL, 2020)

They found that, at 4.4 astronomical units between the two spacecraft, the helical structure of the magnetic cloud had dropped significantly. The team feels that this was possible due to interactions with each other, leaving behind a magnetic cloud that traveled faster than before, reaching up to capture it and compressing it until it reached Ulysses. Arrived.

This may explain why the helical structure of the magnetic cloud in CME became more twisted by the time it reached 5.4 astronomical units – rather than less, as might be expected. Magnetic contact between two clouds can degrade the outer layer, leaving behind a more twisted core.

“What clearly emerges from this analysis is that the second magnetic cloud in 5.4 astronomical units is interacting much more with the first one,” the researchers wrote in their paper.

“As a result, the magnetic structure of the preceding magnetic cloud is strongly deformed. In fact, its mass rotation propagates well from behind the following magnetic cloud and represents a form of D real background background magnetic field rotation. . “

It would be fascinating to see more studies on the subject – and, lucky as observations were, we can get them. Researchers note that we can be seen as the “golden age” of solar physics.

With NASA’s Parker Solar Probe, ESA and JAXA’s BepiColombo and ESA’s Solar Orbiter orbiting the Sun at different distances, it may be just a matter of time before the stars or – spacecraft, in this case – align. Do it

The research has been published in The Astrophysical Journal Letters.

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