Category Archives: sun

sun, sunspots

Diving Into Sunspots

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Sunspots Revealed

First view of what goes on below the surface of sunspots. Lighter/brighter colors indicate stronger magnetic field strength in this subsurface cross section of two sunspots. For the first time, NCAR scientists and colleagues have modeled this complex structure in a comprehensive 3D computer simulation, giving scientists their first glimpse below the visible surface to understand the underlying physical processes. (Click to embiggen.)
First view of what goes on below the surface of sunspots. Lighter/brighter colors indicate stronger magnetic field strength in this subsurface cross section of two sunspots. For the first time, NCAR scientists and colleagues have modeled this complex structure in a comprehensive 3D computer simulation, giving scientists their first glimpse below the visible surface to understand the underlying physical processes. (Click to embiggen.)

Today’s what lots of folk think of as the first day of summer for us northern hemisphere types and first day of winter for the southern hemisphere folks. (It’s actually the mid-point, marking the point when the Sun is the farthest north in its yearly path across the sky.)  Today’s the solstice and FATHER’s DAY here in the U.S…. and just in time for this auspicious occasion, the folks at National Center for Atmospheric Research (NCAR) and the Max Planck Institute for Solar System Research bring us a wonderful computer model of sunspots.  I’m dedicating today’s entry to my dad, who loves to look at sunspots! This one’s for you, Daddy!

The interface between a sunspots umbra (dark center) and penumbra (lighter outer region) shows a complex structure with narrow, almost horizontal (lighter to white) filaments embedded in a background having a more vertical (darker to black) magnetic field. Farther out, extended patches of horizontal field dominate. For the first time, NCAR scientists and colleagues have modeled this complex structure in a comprehensive 3D computer simulation, giving scientists their first glimpse below the visible surface to understand the underlying physical processes. (©UCAR, image courtesy Matthias Rempel, NCAR.
The interface between a sunspot's umbra (dark center) and penumbra (lighter outer region) shows a complex structure with narrow, almost horizontal (lighter to white) filaments embedded in a background having a more vertical (darker to black) magnetic field. Farther out, extended patches of horizontal field dominate. For the first time, NCAR scientists and colleagues have modeled this complex structure in a comprehensive 3D computer simulation, giving scientists their first glimpse below the visible surface to understand the underlying physical processes. (©UCAR, image courtesy Matthias Rempel, NCAR.

The high-res simulations of sunspots are an important tool for scientists to learn more about these blots of seemingly dark regions on the Sun (I say “seemingly” because they’re actually just cooler than the surrounding area, thus appearing darker).  Sunspots are manifestations of the magnetic fields that play across the Sun’s surface.  They’re also closely associated with massive ejections of material that can come straight at Earth and cause things like aurorae, or even go so far as to disrupt our communications networks and power systems. You may have heard of the term “space weather” — well, sunspots are often involved in the processes that cause space weather.  If you’ve been following the Space Weather FX project I’ve been working on for Haystack Observatory, we’ve been talking a lot about the effects of space weather on all kinds of systems.

Creating detailed simulations of sunspots would not have been possible even as recently as a few years ago. But now, we have the latest generation of supercomputers and a growing array of instruments to observe the Sun — and when you marry the two, you can get some amazing simulations of real life. Partly because of such new technology, scientists have made advances in solving the equations that describe the physics of solar processes. The Sun is a complex object, ever-changing and difficult to probe. So, coming up with a computer model is an important step. “This is the first time we have a model of an entire sunspot,” says lead author Matthias Rempel, a scientist at NCAR’s High Altitude Observatory. “If you want to understand all the drivers of Earth’s atmospheric system, you have to understand how sunspots emerge and evolve. Our simulations will advance research into the inner workings of the Sun as well as connections between solar output and Earth’s atmosphere.”

Outward flows from the center of sunspots were discovered a hundred years ago, and ever since then, atmospheric physicists have been working on explanations for the very complex structures they see in sunspots. This includes the fact that their numbers rise and fall during each 11-year solar cycle.

The work was supported by the National Science Foundation, NCAR’s sponsor. The research team improved a computer model, developed at MPS, that built upon numerical codes for magnetized fluids that had been created at the University of Chicago.  GO read more about it (and see some of their really COOL videos) at the UCAR/NCAR web site.

solar physics, solar studies, sun

Does the Sun Miss its Spots?

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Minima-lly Invasive Technique for Sounding the Sun

Our pesky Sun has been diabolically withholding its sunspots for the past couple of years, causing solar physicists to wonder what’s going on with this most minimum of sunspot minima.  The Sun goes through an eleven-year cycle of magnetic activity related to the appearance of sunspots, solar flares, and disturbances of the interplanetary environment called space weather.  We’re at a low in solar activity right now, and it’s been just a LITTLE too quite on the Sun.

a computer representation of one of nearly ten million modes of sound wave oscillations of the Sun, showing receding regions in red tones and approaching regions in blue. By measuring the frequencies of many such modes and using theoretical models, solar astronomers can infer much about the internal structure and dynamics of the Sun. Courtesy National Solar Observatory. Click to embignify.
A computer representation of one of nearly ten million modes of sound wave oscillations of the Sun, showing receding regions in red tones and approaching regions in blue. By measuring the frequencies of many such modes and using theoretical models, solar astronomers can infer much about the internal structure and dynamics of the Sun. Courtesy National Solar Observatory. Click to embignify.

All this lack of activity has scientists wondering just what’s going on inside our star that has kept its normally sunny complexion clear. They can’t exactly go out to the Sun and stick some instruments into the solar surface to diagnose the problem. But, they can do the next best thing — study it remotely with the Global Oscillation Network Group facility. GONG and the orbiting SOHO/MDI instrument measure sound waves on the surface of the Sun. Those sound waves are a very good probe of what’s going on inside the Sun — similar to the way a sonogram tells a doctor what’s happening inside your body. GONG and SOHO/MDI are vanguard instruments in the science of helioseismology.

What they are showing scientists is a clear “sonogram” of a jet stream of material that flows from east to west just beneath the Sun’s visible surface.  It’s called a “torsional oscillation” and a new one gets generated near the solar poles every 11 years. Over a period of 17 years,  the stream migrates slowly to the solar equator.  The most telling point abou these streams is that they are associated with the production of sunspots once they reach a critical latitude of 22 degrees.

Two scientists, Rachel Howe and Frank Hill of the National Solar Observatory, have found that the stream associated with the new solar cycle has been moving rather lazily — taking three years to cover a 10 degree range in latitude compared to two years for the last solar cycle. Since the current minimum is now one year longer than usual, Howe and Hill conclude that the extended solar minimum phase may have resulted from the slower migration of the flow.

Now that the stream has finally reached the critical 22 degree latitude, we should be seeing some more solar activity ramping up as time goes by.  It’s not clear why this torsional oscillation slowed down, but the good news is that the Sun’s magnetic dynamo continues to operate, and we’re probably seeing the beginnings of a new solar cycle.