Recent solar flares may test why sun acts up when its cycle wanes 

Posted: September 20, 2017 by oldbrew in research, Solar physics
Tags: ,

Solar flare [credit: NASA]

Even though the current solar cycle (SC 24) is well-known for its relatively low level of sunspots, it can still produce surprisingly powerful bursts of ‘counter-intuitive’ activity, causing solar scientists to put their thinking caps on.

A series of rapid-fire solar flares is providing the first chance to test a new theory of why the sun releases its biggest outbursts when its activity is ramping down, says Science News.

Migrating bands of magnetism that meet at the sun’s equator may cause the biggest flares, even as the sun is going to sleep. A single complex sunspot called Active Region 2673 emitted seven bright flares — powerful bursts of radiation triggered by magnetic activity — from September 4 to September 10.

Four were X-class solar flares, the most intense kind.

The strongest, released at 8:02 a.m. EDT on September 6, was an X9.3. The most powerful flare since 2006 (and the eighth largest since monitoring started in June 1996), it disrupted shortwave radio communication over Africa for up to an hour. It also flung a blob of energetic plasma, called a coronal mass ejection, speeding toward Earth, which sparked auroras the night of September 7 that were visible as far south as Arkansas.

All that activity is counter-intuitive, as the sun is near the end of an unusually weak solar cycle, which began in 2008 (SN: 11/2/13, p. 22). The sun’s magnetic activity waxes and wanes roughly every 11 years, generating more dark sunspots at the peak of the cycle and fewer at the trough.

“This cycle’s a wiener,” says solar physicist Scott McIntosh, director of the High Altitude Observatory at the National Center for Atmospheric Research in Boulder, Colo. When the cycle peaked in 2013, it was already looking like the weakest in a century.

Solar physicists realized in the 1960s that the peak flare rate comes a few years after the sunspot maximum. Even stranger, the strongest flares tend to occur on the cycle’s downslope. The quietest cycles may even produce the biggest flares. The biggest solar storm in recorded history, called the Carrington event, occurred at the end of another especially weak cycle in early September 1859. Modern simulations estimate that flare may have been an X45.

“When you’re descending to a quiescent phase of the cycle and things are getting more organized and simplified, how is it we are getting things this complex?” asks solar physicist Madhulika Guhathakurta, spokesperson for NASA’s Heliophysics Division. “It still remains an interesting question.”

McIntosh has an idea why. In a series of papers, including a 2015 paper in Nature Communications, he and colleagues argued that complex sunspots like AR 2673 and their forceful flares are the result of opposing bands of magnetism vying for supremacy.

Continued here.
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Update: Solar antics

  1. causing solar scientists to put their thinking caps on.

    How about solar scientists putting their guessing caps on?

  2. oldbrew says:

    One problem with the sun is – you can’t go there 😐

  3. craigm350 says:

    Err the sunspot didn’t stop firing away, it was just not earth facing and it’s now rotating back around…

  4. oldbrew says:

    Are Mexico’s two September earthquakes connected?

    Here’s one theory…

    Fluctuations of cosmic-solar radiations are charging the ionosphere. That results in anomalies of geomagnetic field which causes the generation of eddy current. The eddy current heats the rocks in the faults and consequently the shear resistant intensity and the static friction limit of the rocks would decrease. This is the main process that trigger earthquakes and volcanic eruption.

    During solar minimum high energy cosmic radiation can penetrate to a very deep distance below the Earth’s surface, in some case a few hundred kilometers. This is the reason why most if not all earthquakes during solar minimum are deep earthquakes. The stress on the Magnetosphere during solar minimum is higher because the Heliosphere is weaker and more high energy charged particles can penetrate the solar system.

  5. oldbrew says:

    Solar antics
    September 20, 2017

    The sun’s recent activity has caught the interest of scientists and space weather forecasters worldwide, highlighting the need to keep a watchful eye on our star and its awesome power.

    Read more at:

  6. Oldbrew, lots of earthquakes in last week, also Vanuatu, Toga, Fiji, Indonesia, Hawaii, Japan-near well as Mexico and USA. In fact right around the ring of fire.
    I used to look at site on earthquakes and volcanos I think mentioned a few times here but have lost all the bookmarks when I had to reinstall Windows and Mozilla. can anyone help. The site had explanation as well as a map, times and strength (which are on the US Geo physical site) Can anyone help?

  7. Ivan, no that covers mainly USA and does not say much. This shows Australia and the ring of fire around it Notice the big one in Vanuatu and the one South of NZ
    However the site I was looking for shows the world’s earthquakes and volcanoes and tries to relate changes to things like changes to the magnetic fields and solar flares.

  8. Poly says:

    One site which “shows the world’s earthquakes and volcanoes and tries to relate changes to things like changes to the magnetic fields and solar flares” is;

  9. oldbrew says:

    Last big eruption in 1963-4 killed ~1700.

    Earthquake strikes off coast of Bali, residents evacuated
    Yahoo7 / September 21st, 2017

    A 5.7 magnitude earthquake has struck off the coast of Bali, Indonesia.

    It was detected northeast of Kemeduran on Thursday, the US Geological Survey confirmed.

  10. Brett Keane says:

    “One of these came during the Cassini mission’s final phase, the so-called Grand Finale where it made a total of 22 daring dives through the 1,500-mile-wide (2,400-km) gap between the planet and its rings. It was through these lunges that Cassini revealed the Saturn’s magnetic field has no discernible tilt. This is a something of a curveball for planetary scientists, who have generally believed that some degree of tilt is a necessary for a planet to sustain a magnetic field.”

  11. oldbrew says:

    Brett K – perhaps they could call it the liquid metallic hydrogen problem 😉