The struggle between two magnetic structures may cause solar eruptions
By developing a model to understand solar eruptions, it may be easier to predict them
Researchers have determined that a magnetic power struggle could be behind all solar eruptions.
The findings, detailed in a study published in the journal Nature on Wednesday, might improve our ability to predict solar flares.
A solar flare is one of the largest explosive events in our solar system. Appearing as brightened areas on the sun, solar flares are intense bursts of radiation produced as sunspots release magnetic energy. They can pass in a matter of minutes – or last for hours.
Although solar flares don’t directly harm us on Earth, they have the potential to disrupt the technology we rely on, like GPS, radar, high-frequency radio communications between aircraft and air traffic control, and communication technology that relies on satellites such as cell phones and electricity grid distribution networks.
They can also affect the International Space Station and anything else in the near-space environment of Earth’s upper atmosphere.
Solar flares are considered part of “space weather,” the conditions affecting the space around Earth that are usually caused by the sun. Flares are sometimes accompanied by coronal mass ejections, magnetic plasma bubbles that can reach Earth and cause an impact.
By studying one of several major solar flares that occurred in 2014, French researchers discovered the presence of a mechanism within the eruption. The October 24, 2014, flare affected some radio communication systems, like plane and radar systems, according to the US National Weather Service’s Space Weather Prediction Center.
Although researchers knew from previous research that the sun’s magnetic field was responsible for solar eruptions, the magnetic field itself is invisible. They developed a way to make it visible using models of the solar corona above where the eruptions take place. This created a “magnetic ultrasound scan,” allowing the researchers to see the properties present in the days leading up to the “birth” of the eruption, Tahar Amari wrote in an email. Amari is study author and director of the Centre de Physique Theorique, Ecole polytechnique in France.
The researchers discovered that a structure resembling a magnetic “cage” appears, and a magnetic “rope” forms inside it. The eruption happens when the rope releases an attack on the cage and the cage resists it. That relationship determines the power and magnitude of the flare, which researchers hope to be able to use in predicting the maximum energy that will be released.
“The cage is strongly rooted on the magnetic (sun) spots and is created with the spots,” Amari said. “The rope develops by two processes, one associated by its origin emerging from the surface and the other amplifying its properties related to the motions occurring on the surface of the sun.”
The resistance between the cage and the rope happens because the cage has gained pressure and tension force supplied by the magnetic field. When the rope becomes unstable due to its electric current, the cage is able to contain it.
In the case of the October 2014 flare, the rope was confined within multiple layers of the cage. The rope didn’t have enough energy to break through all of the layers of the cage to eject a magnetic plasma bubble, but it did destroy part of the cage. This is what caused the release of radiation that led to disruptions on Earth.
Using satellite data of the sun’s magnetic field, Amari hopes researchers can use the model to “scan” the magnetic structure at any time to look for signs of the cages and ropes. They can input that data into another model to look at the stability and predict the type of eruption.
The National Weather Service is able to predict space weather using the Space Weather Prediction Center, on a scale from hours to weeks. But Amari believes that his team’s method expands on that and provides a bigger picture.
Separately, NASA’s GOLD mission, which will explore the zone between Earth’s atmosphere and the lowest reaches of space, also seeks to investigate space weather.
Although not all space weather has an impact on Earth, some has had the potential to cause blackouts, like the Quebec power outage of 1989, when the Hydro-Quebec power grid failed during a geomagnetic storm, causing a widespread blackout lasting nine hours.
A study published last year in the journal Space Weather estimates that solar storm-caused blackouts could cost the US tens of billions of dollars.