Sun experiences seasonal changes, new research finds

April 7, 2015
A number of NASA instruments captured detailed images of this coronal mass ejection on Aug. 31, 2012. Although CMEs can damage sensitive technological systems, this one just struck a glancing blow to Earth's atmosphere. New research that quasi-annual variations in solar activity, which may help experts better forecast these powerful events. Credit: NASA

The Sun undergoes a type of seasonal variability with its activity waxing and waning over the course of nearly two years, according to a new study by a team of researchers led by the National Center for Atmospheric Research (NCAR). This behavior affects the peaks and valleys in the approximately 11-year solar cycle, sometimes amplifying and sometimes weakening the solar storms that can buffet Earth's atmosphere.

The quasi-annual variations appear to be driven by changes in the bands of strong magnetic fields in each solar hemisphere. These bands also help shape the approximately 11-year solar cycle that is part of a longer cycle that lasts about 22 years.

"What we're looking at here is a massive driver of solar storms," said Scott McIntosh, lead author of the new study and director of NCAR's High Altitude Observatory. "By better understanding how these activity bands form in the Sun and cause seasonal instabilities, there's the potential to greatly improve forecasts of space weather events."

The overlapping bands are fueled by the rotation of the Sun's deep interior, according to observations by the research team. As the bands move within the Sun's northern and southern hemispheres, activity rises to a peak over a period of about 11 months and then begins to wane.

The quasi-annual variations can be likened to regions on Earth that have two seasons, such as a rainy season and a dry season, McIntosh said.

The study, published this week in Nature Communications, can help lead to better predictions of massive geomagnetic storms in Earth's outer atmosphere that sometimes disrupt satellite operations, communications, power grids, and other technologies.

The research was funded by NASA and the National Science Foundation, which is NCAR's sponsor.

Bands of magnetized solar material march toward the sun's equator. The way the bands in each hemisphere interact leads to a 330-day cycle of waxing and waning activity on the sun that can be as strong as the more well-studied 11-year solar cycle. Credit: S. McIntosh

A "jet stream" in the Sun

The new study is one of a series of papers by the research team that examines the influence of the magnetic bands on several interrelated cycles of solar magnetism. In a paper last year in Astrophysical Journal, the authors characterized the approximately 11-year sunspot cycle in terms of two overlapping parallel bands of opposite magnetic polarity that slowly migrate over almost 22 years from high solar latitudes toward the equator, where they meet and terminate.

McIntosh and his co-authors detected the twisted, ring-shaped bands by drawing on a host of NASA satellites and ground-based observatories that gather information on the structure of the Sun and the nature of and coronal mass ejections (CMEs). These observations revealed the bands in the form of fluctuations in the density of magnetic fuel that rose from the solar interior through a transition region known as the tachocline and on to the surface, where they correlated with changes in flares and CMEs.

In the new paper, the authors conclude that the migrating bands produce seasonal variations in solar activity that are as strong as the more familiar 11-year counterpart. These quasi-annual variations take place separately in both the northern and southern hemispheres.

"Much like Earth's jet stream, whose warps and waves have had severe impact on our regional weather patterns in the past couple of winters, the bands on the Sun have very slow-moving waves that can expand and warp it too," said co-author Robert Leamon, a scientist at Montana State University. "Sometimes this results in magnetic fields leaking from one band to the other. In other cases, the warp drags magnetic fields from deep in the solar interior, near the tachocline, and pushes them toward the surface."

The surges of magnetic fuel from the Sun's interior catastrophically destabilize the corona, the Sun's outermost atmosphere. They are the driving force behind the most destructive .

"These surges or 'whomps' as we have dubbed them, are responsible for over 95 percent of the large flares and CMEs—the ones that are really devastating," McIntosh said.

The quasi-annual variability can also help explain a cold-war era puzzle: why do powerful solar flares and CMEs often peak a year or more after the maximum number of sunspots? This lag is known as the Gnevyshev Gap, after the Soviet scientist who first reported it in the 1940s. The answer appears to be that seasonal changes may cause an upswing in solar disturbances long after the peak in the solar cycle.

Researchers can turn to advanced computer simulations and more detailed observations to learn more about the profound influence of the bands on solar activity. McIntosh said this could be assisted by a proposed network of satellites observing the Sun, much as the global networks of satellites around Earth have helped advance terrestrial weather models since the 1960s.

"If you understand what the patterns of are telling you, you'll know whether we're in the stormy phase or the quiet phase in each hemisphere," McIntosh said. "If we can combine these pieces of information, forecast skill goes through the roof."

Explore further: Dazzled by the bright Southern Lights

More information: The solar magnetic activity band interaction and instabilities that shape quasi-periodic variability, Nature Communications, 2015. www.nature.com/ncomms/2015/150407/ncomms7491/full/ncomms7491.html

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8 comments

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Gimp
2.8 / 5 (14) Apr 07, 2015
Of course none of this affects the output of radiant energy and has a net zero effect on the Earth or it's climate. Now if we could tax the Sun and ask it to behave according to our wishes and desires........
Nnnrj
1.5 / 5 (8) Apr 07, 2015
Influences of Jupiter and Saturn, beyond the solar system rising to the center of the galaxy
rhsthjnty
4.3 / 5 (6) Apr 07, 2015
Influences of Jupiter and Saturn, beyond the solar system rising to the center of the galaxy


Jupiter has close to a 12 year orbit and Saturn has a 29 year orbit. Now, what the hell are you talking about?
Nnnrj
1 / 5 (6) Apr 07, 2015
"Jupiter has close to a 12 year orbit and Saturn has a 29 year orbit. Now, what the hell are you talking about?

is what happens when using wikipedia as the sole source of information
search for sunspot cycle forecast and planetary correlations
be more polite, you might find some collaboration around

and do not disturb me
Dethe
1 / 5 (4) Apr 07, 2015
why do powerful solar flares and CMEs often peak a year or more after the maximum number of sunspots
I tried to answer it here - the shifting of barycenter bellow surface of Sun stops the circulation of solar plasma which leads to its overheating in similar way, like the heating of pot in the microwave. When barycenter leaves the volume of Sun, the circullation of solat plasma gets restored, which manifest itself with sun spots turbulences. The overheated plasma raises to the surface of Sun like the bubbles of vapor and explodes there in solar flares.
Hat1208
5 / 5 (6) Apr 08, 2015
@rhsthjnty

I'm with you, "What the hell is Nnnrj talking about?".
Nnnrj
not rated yet Apr 09, 2015
até parece que não sei quem é você e o que esta querendo,
te vire, estude sozinho ou morra na sua ignorância, quero mais é que tu não compreenda nada do que eu digo
Dethe
not rated yet Apr 09, 2015
What you can see are the convective cells which can be seen in the atmosphere of Earth and another planets (Jupiter/Saturn bands, etc). The jet stream has also an analogy at the Earth..
Influences of Jupiter and Saturn, beyond the solar system rising to the center of the galaxy
The 330 day period has nothing to do with Jupiter or Saturn, the center of galaxy the less.

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