The most prominent solar flares aren't always the most impactful.

A solar flare captured by NASA’s Solar Dynamics Observatory on October 1, 2015 at 8:12 p.m. Credit: NASA/SDO

Although many studies have compared the magnetic properties of confined and bursting solar flares, few have considered the thermodynamic properties of confined flares and even fewer compared to bursting flares.

Maria Kazachenko, an assistant professor in the University of Colorado Boulder Department of Astrophysical and Planetary Sciences, is one of the few people who has explored this topic. In a paper published I The Astrophysical Journal And featured on AAS Nova, he conducted a study quantifying thermodynamics. of hundreds of solar flares.

Solar flares are massive bursts of electromagnetic radiation from the Sun. It occurs when energy stored in magnetic fields, usually above sunspots, is suddenly released. Some involve flames. (CME), in which a large amount of charged particles, or plasma, is ejected.

Some of the study’s findings confirm the findings of earlier inquiries. However, the paper also includes new information suggesting that confined flares, or flares not associated with CMEs, may be more efficient at accelerating particles and therefore producing ionizing radiation.

What is a solar flare?

Solar flares are caused by the Sun’s magnetic fields, which are strongest in dark regions called sunspots. When disabled, these fields look like loops. However, when the Sun’s surface currents begin to shear and twist the sunspots to which they are bound, the magnetic fields also twist.

“You can think of it like a rubber band that you start to twist,” Kazachenko explains. “At some point, you cut it, then … the energy will be released and you’ll get a shock on your hand.”

Credit: NASA

Just as the elastic energy of a rubber band is released when it is cut, a portion of the Sun’s magnetic energy is released during a process called . Magnetic reconnection can take a variety of forms, but “one of the simplest configurations,” Kazachenko says, “is when you have two field lines of opposite direction pushing against each other …, like a rubber band that suddenly cut off.”

The free magnetic energy that is released during magnetic reconnection is stored in the plasma current. Electric currents produce magnetic fields, as seen in electromagnets, and charged particles move within the Sun’s plasma in a similar manner.

Confined and bursting flames

While some solar flares are associated with CMEs, where plasma is ejected from the solar atmosphere and into space, others are not. If a solar flare is associated with a CME, it is considered an eruption. If it has no corresponding CME, it is considered restricted. However, the difference between the two is deeper than that, because the mechanisms that determine whether a flare is confined or explosive may also decide how quickly the magnetic fields will reconnect and how long it will last. It will emit hard X-ray and gamma-ray radiation.

As their name suggests, confined flares are unable to escape due to the confining effects of the Sun’s atmosphere. These effects, called stripping fields, are also magnetic. Therefore, functional areas with more It also has strong stripping fields and hence is less likely to explode.

According to Kazachenko, this explains why the confined flames he studied had higher temperatures and recombined faster than burst flames of the same peak X-ray flux: “In confined flames, your Reconnection is reduced because you have a very strong strip. The field in the active region that doesn’t allow the structure to move up… the fields are stronger downstream, so the reconnection proceeds much faster.”

Although the importance of rapid reconnection may not be immediately apparent. explains, “Because the higher correlation rate leads to more accelerated ions and electrons, large confined flame ionizing electromagnetic radiation can be more efficient than burst flames.”

This does not mean that much energy is released during the reconnection of a finite flare. In fact, implosion flames have the same amount of recombined flux as confined flames. Rather, because energy is released more rapidly in confined flares, they can more efficiently accelerate ions and electrons from the Sun’s plasma.

Space weather in this solar system and beyond

When it comes to space weather, CMEs and They can often cause the most attention. This is for a good reason: Although CMEs are rare to reach Earth, when they do, the consequences are dire.

I , a geomagnetic storm will damage or destroy electrical transmission equipment, causing widespread blackouts. Additionally, such a storm would disrupt certain types of communications, damage satellite hardware, and expose astronauts and high-altitude aviators to potentially lethal radiation. Although these are only predictions, their evidence is based on the geomagnetic storm of 1859, the effects of which were evident, causing sparks and fires in telegraph stations.

Research like Kazachenko’s contributes to a broader understanding of how solar flares work, which could one day allow scientists to more accurately predict when they will occur and therefore People can avoid the worst consequences of geomagnetic storms by giving them time to take precautions. However, this study has broader implications as well.

“What happens on other stars?” Kazachenko asks. “Are there flares? Are there CMEs? From recent studies, it looks like there are thousands of flares, but CMEs, coronal mass ejections, are very difficult to determine.”

Although it is possible that stars like the Sun regularly undergo CMEs and scientists and researchers have simply failed to detect most of them, current evidence suggests that limited flares may occur in the space weather of other solar systems. play a more important role than For one reason, a seemingly low-impact type of solar flare can determine whether exoplanets are habitable—of great interest to astronomers looking for exoplanets suitable for colonization.

“So, this is a very fundamental question, both … for protecting our instruments, but also for understanding other planets,” Kazachenko says.

Future Inquiry

While Kazachenko has discovered a unique property of finite There is still work to be done, she says. His studies show that confined flames rapidly reattach magnetic fields and potentially accelerate charged particles more efficiently than exploding particles, but the properties of these particles are beyond his scope. .

Kazachenko says there should be a follow-up study. “Where you really look at the population of particle acceleration statistics in both groups of flares … but I think that’s where the future lies: not just looking at a single event in great detail, but taking advantage of the amazing observations that have been made.” We’re getting it now. Many different satellites are flying there, such as the new satellite launched by NASA and the European Space Agency called the Solar Orbiter.”

More information:
Maria de Kazachenko, Database of Magnetic and Thermodynamic Properties of Confined and Bursting Solar Flares, The Astrophysical Journal (2023). DOI: 10.3847/1538-4357/ad004e

Reference: The most outstanding solar flare eruptions are not always the most impressive (2024, February 21) https://phys.org/news/2024-02-outstanding-solar-flare-eruptions-21 February 2024 Retrieved from influential.html

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