NASA sun data helps new model predict big solar flares

Date:
July 31, 2020
Source:
NASA/Goddard Space Flight Center
Summary:
Scientists have developed a new model that successfully predicted
seven of the Sun's biggest flares from the last solar cycle, out
of a set of nine. With more development, the model could be used to
one day inform forecasts of these intense bursts of solar radiation.



FULL STORY ========================================================================== Using data from NASA's Solar Dynamics Observatory, or SDO, scientists
have developed a new model that successfully predicted seven of the Sun's biggest flares from the last solar cycle, out of a set of nine. With
more development, the model could be used to one day inform forecasts
of these intense bursts of solar radiation.


==========================================================================
As it progresses through its natural 11-year cycle, the Sun transitions
from periods of high to low activity, and back to high again. The
scientists focused on X-class flares, the most powerful kind of these
solar fireworks. Compared to smaller flares, big flares like these are relatively infrequent; in the last solar cycle, there were around 50. But
they can have big impacts, from disrupting radio communications and power
grid operations, to -- at their most severe -- endangering astronauts
in the path of harsh solar radiation.

Scientists who work on modeling flares hope that one day their efforts
can help mitigate these effects.

Led by Kanya Kusano, the director of the Institute for Space-Earth Environmental Research at Japan's Nagoya University, a team of scientists
built their model on a kind of magnetic map: SDO's observations of
magnetic fields on the Sun's surface. Their results were published in
Science on July 30, 2020.

It's well-understood that flares erupt from hot spots of magnetic
activity on the solar surface, called active regions. (In visible light,
they appear as sunspots, dark blotches that freckle the Sun.) The new
model works by identifying key characteristics in an active region, characteristics the scientists theorized are necessary to setting off
a massive flare.

The first is the initial trigger. Solar flares, especially X-class
ones, unleash huge amounts of energy. Before an eruption, that energy
is contained in twisting magnetic field lines that form unstable arches
over the active region.

According to the scientists, highly twisted rope-like lines are a
precursor for the Sun's biggest flares. With enough twisting, two
neighboring arches can combine into one big, double-humped arch. This
is an example of what's known as magnetic reconnection, and the result
is an unstable magnetic structure -- a bit like a rounded "M" -- that
can trigger the release of a flood of energy, in the form of a flare.

Where the magnetic reconnection happens is important too, and one of the details the scientists built their model to calculate. Within an active
region, there are boundaries where the magnetic field is positive on one
side and negative on the other, just like a regular refrigerator magnet.

"It's similar to an avalanche," Kusano said. "Avalanches start with
a small crack. If the crack is up high on a steep slope, a bigger
crash is possible." In this case, the crack that starts the cascade
is magnetic reconnection. When reconnection happens near the boundary,
there's potential for a big flare. Far from the boundary, there's less available energy, and a budding flare can fizzle out -- although, Kusano pointed out, the Sun could still unleash a swift cloud of solar material, called a coronal mass ejection.

Kusano and his team looked at the seven active regions from the last
solar cycle that produced the strongest flares on the Earth-facing side
of the Sun (they also focused on flares from part of the Sun that is
closest to Earth, where magnetic field observations are best). SDO's observations of the active regions helped them locate the right magnetic boundaries, and calculate instabilities in the hot spots. In the end,
their model predicted seven out of nine total flares, with three false positives. The two that the model didn't account for, Kusano explained,
were exceptions to the rest: Unlike the others, the active region they
exploded from were much larger, and didn't produce a coronal mass ejection along with the flare.

"Predictions are a main goal of NASA's Living with a Star program
and missions," said Dean Pesnell, the SDO principal investigator at
NASA's Goddard Space Flight Center in Greenbelt, Maryland, who did not participate in the study. SDO was the first Living with a Star program
mission. "Accurate precursors such as this that can anticipate significant solar flares show the progress we have made towards predicting these
solar storms that can affect everyone." While it takes a lot more work
and validation to get models to the point where they can make forecasts
that spacecraft or power grid operators can act upon, the scientists have identified conditions they think are necessary for a major flare. Kusano
said he is excited to have a promising first result.

"I am glad our new model can contribute to the effort," he said.


========================================================================== Story Source: Materials provided by
NASA/Goddard_Space_Flight_Center. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Kanya Kusano, Tomoya Iju, Yumi Bamba, Satoshi Inoue. A physics-based
method that can predict imminent large solar flares. Science,
2020; 369 (6503): 587 DOI: 10.1126/science.aaz2511 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200731135600.htm

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