The Sun’s coronal tail wags its photospheric dog

Posted: October 13, 2016 by oldbrew in research, Solar physics
Tags: ,

Solar flare erupting from a sunspot [image credit:]

Solar flare erupting from a sunspot [image credit:]

Researchers have unearthed a cause-and-effect conundrum for solar physicists, involving solar flares. reports.

Solar physicists have long viewed the rotation of sunspots as a primary generator of solar flares – the sudden, powerful blasts of electromagnetic radiation and charged particles that burst into space during explosions on the sun’s surface. Their turning motion causes energy to build up that is released in the form of flares.

But a team of NJIT scientists now claims that flares in turn have a powerful impact on sunspots, the visible concentrations of magnetic fields on the sun’s surface, or photosphere. In a paper published in Nature Communications this week, the researchers argue that flares cause sunspots to rotate at much faster speeds than are usually observed before they erupt.

Their observations, based on high-resolution images captured through NJIT’s 1.6 meter New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), come as something of a surprise. The sun’s outer layer, or corona, where flares are released, has a plasma density about a hundred million times smaller than that of the photosphere.

“It’s analogous to the tail wagging the dog. The lower-density regions are much less energetic and forceful,” said Chang Liu, a research professor of physics at NJIT and the principal author of the study, “Flare differentially rotates sunspot on Sun’s surface.”

“We do think the rotation of sunspots builds up magnetic energy that is released in form of solar flares, but we have also observed conclusively that flares can cause sunspots to rotate about 10 times faster,” he added. “This highlights the powerful, magnetic nature of solar flares.”

Haimin Wang, a distinguished professor of physics at NJIT and a co-author of the paper, said the observations will prompt scientists to revisit the mechanisms of flares – and the basic physics of the Sun – in a fundamental way.

“We used to think that the surface’s magnetic evolution drives solar eruptions. Our new observations suggest that disturbances created in the solar outer atmosphere can also cause direct and significant perturbations on the surface through magnetic fields, a phenomenon not envisioned by any major contemporary solar eruption models. This has immediate and far-reaching implications in understanding energy and momentum transportation in eruptions on the Sun and other stars,” Wang said. “We will continue to study, and possibly re-interpret, the relationship between the different layers of the Sun.”

Full report: The Sun’s coronal tail wags its photospheric dog |

  1. RoswellJohn says:

    It seemed obvious to me, a low level solar researcher back in the 60s, that flares came FROM the corona, where the density and temperature reached fusion levels, but I never saw any hint of that from mainstream solar physics. Now these researchers are just saying it, as if it was well known. As for that blast from above affecting photosphere sunspots; that’s new and interesting!

  2. oldbrew says:

    Solar Cycle Mystery Solved ?
    Guest Blogger / 7 hours ago October 13, 2016
    Guest essay by David Archibald

  3. Geoff Sharp says:

    It would seem that Archibald and Fix have reproduced my work?

    I hope I am cited correctly, if not the journal will be getting some correspondence.

  4. oldbrew says:

    SD news: Proxima Centauri might be more sunlike than we thought

    In August astronomers announced that the nearby star Proxima Centauri hosts an Earth-sized planet (called Proxima b) in its habitable zone. At first glance, Proxima Centauri seems nothing like our Sun. It’s a small, cool, red dwarf star only one-tenth as massive and one-thousandth as luminous as the Sun. However, new research shows that it is sunlike in one surprising way: it has a regular cycle of starspots.

    The cycle lasts around 7 years.

    “The existence of a cycle in Proxima Centauri shows that we don’t understand how stars’ magnetic fields are generated as well as we thought we did,” says Smithsonian co-author Jeremy Drake.

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