Solving sunspot mysteries

June 3, 2014 by Alexander Kosovichev
Images of sunspot structure on the solar surface (top left) and at different heights above the surface (bottom row) obtained from the New Solar Telescope at Big Bear Solar Observatory (NJIT) on 29 September, 2013. The surface images show a dark central part (umbra) surrounded by filamentary penumbra, and an intrusion of hot plasma in the umbra (“light bridge”). The atmospheric images reveal fast plasma jets (bottom left), material accretion in the form of dense plasma sheets (second  from the left) and very dynamic fibrils (two right panels). The sunspot  activity is exceptionally strong in the “light bridge” area, above which the IRIS satellite detected sharply enhanced UV radiation (top right image). Credit: Santiago Vargas Domínguez & Alexander Kosovichev (BBSO/NJIT)

Multi-wavelength observations of sunspots with the 1.6-meter New Solar Telescope at Big Bear Solar Observatory (BBSO) in California and aboard NASA's IRIS spacecraft have produced new and intriguing images of high-speed plasma flows and eruptions extending from the Sun's surface to the outermost layer of the solar atmosphere, the corona. Operated by New Jersey Institute of Technology (NJIT), BBSO houses the largest ground-based telescope dedicated to solar research.

On June 2, NJIT researchers reported on the acquisition of these images at the 224th meeting of the American Astronomical Society (AAS), held in Boston, Massachusetts. The high-definition video acquired at BBSO provides unique 3D views of a sunspot, revealing rapidly rotating plasma rolls, powerful shocks, and widespread plasma eruptions driven by solar-energy flux and controlled by intense magnetic fields. These leading-edge observations show that sunspots are far more complex and dynamic than previously believed.

Sunspots, first seen by Galileo more than 400 years ago as dark blemishes on the Sun, are still one of the greatest mysteries of astronomy. It has been known for more than a century that sunspots are compact, concentrated magnetic fields and that they appear dark because the magnetism prevents heat from rising to the surface from the superhot interior. But why these magnetic fields become so concentrated and compacted in structures that remain stable for days and sometimes weeks in a very turbulent environment is a mystery.

Sunspots can be the size of Earth or as big as Jupiter. Typical sunspots are nearly round with a very dark and relatively "cold" umbra (7,000 degrees Fahrenheit compared to the 10,000-degree solar surface) surrounded by a less dark and warmer penumbra. However, there are no external forces on the Sun that could hold these giant magnetic structures together. They appear and are organized by their own induced forces. Understanding the processes of such self-organization in the hot turbulent plasma is of fundamental importance for physics and astrophysics.

Investigating sunspots is much more than a matter of curiosity and the desire to increase the fund of basic scientific knowledge. When sunspots that are close to each other have magnetic fields with opposite polarities, they can produce powerful flares and solar storms. On Earth, this can severely damage communications and power infrastructure. Similar but even more intense magnetic phenomena have been detected on other stars, which may be a factor hindering the development of life elsewhere in our galaxy.

Solving sunspot mysteries

At the AAS meeting, the NJIT researchers presented video chronicling several hours in the life of an isolated sunspot that did not generate solar flares. But the roiling action revealed was a transformative view of sunspots as static-equilibrium structures maintaining a balance between magnetic force and gas pressure.

The telescope at BBSO that made these unparalleled observations possible was completed in 2009 under the leadership of Philip Goode, NJIT distinguished professor of physics and at the time director of the university's Center for Solar-Terrestrial Research. The telescope is equipped with adaptive optics that include a deformable mirror to compensate for the atmospheric distortion of images in real time. Images are captured with very fast cameras in 15-second "bursts" of 100 images, and then processed using a speckle reconstruction technique to improve sharpness.

The imaging and data-acquisition systems were developed by the BBSO engineering team led by Wenda Cao, NJIT associate professor of physics and the observatory's associate director. The data recorded is unique in that it comprises a long, uninterrupted series that allows researchers to look at a sunspot's life cycle and activity with unprecedented spatial resolution. Previously, only short series or snapshots with such resolution were available.

The sunspot data shared at the AAS meeting was obtained on September 29, 2013. The solar surface, the photosphere, was imaged using a red-light filter in the range of molecular TiO lines, to achieve the best contrast in the sunspot's umbra. Simultaneously, scanning the hydrogen H-alpha spectral line facilitated imaging at five different wavelengths. The H-alpha data yielded images of plasma flows at various layers in the , enabling the NJIT researchers to obtain a dynamic 3D view of the sunspot. The BBSO data was compared with UV images of the high and hot atmosphere obtained by NASA's IRIS satellite for the same region. This joint observing program allows investigation of the origins of solar UV radiation.

The data as presented in the high-definition video shown at the meeting reveals small-scale activity of a generally "quiet" sunspot in unprecedented detail. Remarkably, the organization of small-scale substructures is comparable to that seen at larger scales, indicating the existence of large-scale dynamics which control the formation and stability of sunspots. In particular, the TiO images provide the first detailed view of the darkest regions of sunspots, revealing rapidly rotating convective rolls in the penumbra and similarly rotating relatively bright "umbral dots." The umbral dots form an evolving pattern clearly linked to the outer penumbra structure. Such evolution provides evidence for large-scale flows that probably play a key role in the self-organization and stability of sunspots.

The most prominent features in the Sun's chromosphere are periodic pulses—shocks generated by sunspots at intervals of about three minutes. The shocks, which travel into the high solar atmosphere with a speed of about 45,000 miles per hour, are observed by the IRIS spacecraft as UV flashes above the sunspot. The sunspot's umbra is covered by ubiquitous eruptions—plasma jets that may contribute to the shocks detected.

The most significant UV emissions and violent motion are observed above the area where the penumbra intrudes into the umbra, the so-called "light bridge." It is likely that this effect is related to anomalies in the sunspot's magnetic topology, and requires further investigation. Some of the most dramatic events are high-speed plasma jets originating from the penumbra, as well as the apparent chromospheric accretion of dense plasma sheets into the . The origin of the accretion flows is another puzzle.

Looking ahead, the NJIT researchers plan to use quantitative diagnostics to study plasma and properties through analysis of polarized solar light, and to integrate realistic numerical simulations performed on supercomputer systems into their work. Comparable simulations at the NASA Ames Research Center have revealed a magnetic self-organization process that caused a compact "mini-spot" magnetic structure to form through the interaction of vortex tubes below the visible .

Explore further: Discovering a hidden source of solar surges

Related Stories

Discovering a hidden source of solar surges

June 3, 2014

Cutting-edge observations with the 1.6-meter telescope at Big Bear Solar Observatory (BBSO) in California have taken research into the structure and activity of the Sun to new levels of understanding. Operated by New Jersey ...

NASA's SDO sees giant January sunspots

January 7, 2014

An enormous sunspot, labeled AR1944, slipped into view over the sun's left horizon late on Jan. 1, 2014. The sunspot steadily moved toward the right, along with the rotation of the sun, and now sits almost dead center, as ...

Quiet Interlude in Solar Max

March 8, 2013

( —Something unexpected is happening on the Sun. 2013 was supposed to be the year of "solar maximum," the peak of the 11-year sunspot cycle. Yet 2013 has arrived and solar activity is relatively low. Sunspot numbers ...

Recommended for you

Video: A colorful 'landing' on Pluto

January 20, 2017

What would it be like to actually land on Pluto? This movie was made from more than 100 images taken by NASA's New Horizons spacecraft over six weeks of approach and close flyby in the summer of 2015. The video offers a trip ...

Freeze-dried food and 1 bathroom: 6 simulate Mars in dome

January 20, 2017

Crammed into a dome with one bathroom, six scientists will spend eight months munching on mostly freeze-dried foods—with a rare treat of Spam—and have only their small sleeping quarters to retreat to for solace.

Image: Wavemaker moon Daphnis

January 20, 2017

The wavemaker moon, Daphnis, is featured in this view, taken as NASA's Cassini spacecraft made one of its ring-grazing passes over the outer edges of Saturn's rings on Jan. 16, 2017. This is the closest view of the small ...

The evolution of massive galaxy clusters

January 20, 2017

Galaxy clusters have long been recognized as important laboratories for the study of galaxy formation and evolution. The advent of the new generation of millimeter and submillimeter wave survey telescopes, like the South ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) Jun 03, 2014
Sunspots are still one of the greatest mysteries of astronomy.

But why these magnetic fields become so concentrated and compacted in structures that remain stable for days and sometimes weeks in a very turbulent environment is a mystery.

The origin of the accretion flows is another puzzle.

"I cannot forecast to you the action of the plasma. It is a riddle, wrapped in a mystery, inside an enigma; but perhaps there is a key. That key is embracing Alfven and the theories he developed through a lifetime of experimentation" Winston Churchill (sorta)

Remarkably, the organization of small-scale substructures is comparable to that seen at larger scales, indicating the existence of large-scale dynamics

Why is that remarkable? The scalability of plasma is well understood by some, but apparently not those who claim to study it.

high-speed plasma flows; rapidly rotating plasma rolls; large-scale flows; vortex tubes

The "key" is electric currents, surprise?
1 / 5 (2) Jun 03, 2014
Many phenomena on the sun and sunspots , are only indicators of something that has a specific cause . Science does not make much effort to clarify the true causes of the phenomenon in the sun . How many times do I have to tell someone that there is a full explanation of almost all of these phenomena and their causes . Why does not exist anywhere in any scientific institution the possibility that it can offer a solution to this phenomenon. What are they afraid of science when , behold, I , I offer a safe solution , but no one was interested. Is it a complete science came to the ideas of total abstinence strangers , who offer the right solution . All this happens in the sun and have as a result of damage to our planet and climate change related to these phenomena , has other causes. Is there anyone who wants to make a contract , by which it can solve THIS ENIGMA .
I offer this solution " if it is not true , then I'm crazy , but if it is true , and no one will accept it , then everyone involved in it , crazy . Gotta say this, because I'm at over 100 sites offering solved and but there is no one who is interested. everyone only wanted me to publish , but above all to pay to get it ? ? ?
Consider who is crazy here . Sorry if I brought this to the fact that I have to make a statement .

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.