Solar physicists from Lockheed
Martin [NYSE: LMT], and The Institute of Theoretical
Astrophysics of the University of Oslo have analyzed the
highest resolution images ever taken near the solar disk
center and found surprising new small-scale magnetic field
structures. Their results, which were reported yesterday at
the American Astronomical Society’s meeting in Denver,
address long-standing issues on the formation and decay of
sunspots and the forecasting of magnetic activity such as
solar flares and coronal mass ejections. Such activity
influences the upper atmosphere and magnetosphere of Earth
and can damage satellites in orbit.
"These new images and magnetic field measurements show that
the Sun can still surprise us when we look at things 100 km
(62 mile) in size," said Dr. Tom Berger, principal
investigator on the study, and solar physicist at the
Lockheed Martin Solar and Astrophysics Lab (LMSAL) at the
company’s Advanced Technology Center in Palo Alto, Calif.
"Using the Swedish one-meter Solar Telescope (SST) on the
island of La Palma, Spain, we have discovered new ways in
which the smallest ‘elements’ of the Sun’s magnetic field
arrange themselves in the turbulent flowfields of the Sun’s
surface.
The Sun undergoes an 11-year cycle in which its magnetic
flux, as seen most prominently in the form of dark sunspots,
peaks and wanes. Sunspots demarcate highly magnetic
‘active regions’ in the solar atmosphere that unleash
flares and coronal mass ejections. When coronal mass
ejections are directed toward Earth they can damage
satellites in orbit, expose high flying airplanes to
radiation, and even adversely effect power stations on the
ground. Scientists still do not understand how active
regions are formed, why they vary with a roughly 11-year
period, or how and when flares and mass ejections occur.
In addition to the large and obvious sunspots, active
regions contain a myriad of smaller magnetic structures
surrounding the sunspots. These smaller structures are much
more dynamic than sunspots, constantly emerging, moving,
and rearranging due to their interactions with the
convective flowfield. This constant motion in the small-
scale ‘plage’ fields around sunspots builds up magnetic
‘tension’ in the larger scale magnetic fields, like a
spring winding tighter and tighter. The magnetic ‘spring’
eventually snaps causing ‘magnetic reconnection’ and
subsequent flares and/or mass ejections.
Scientists are uncertain of the origin of the small-scale
magnetic structures on the Sun. Some of the structure
clearly originates from sunspots as they decay away over
their lifetime. But small-scale structure is found all over
the Sun, often far from sunspots in regions of ‘quiet Sun.’
Sunspots are believed to be formed by a ‘global-scale
dynamo’ system located about 30% of the way down to the
Sun’s center, at the bottom of the ‘convection zone.’
However recent observational and theoretical evidence
suggests that most of the small-scale magnetic flux in the
quiet Sun may be generated by a ‘local dynamo’ mechanism
seated in the upper convection zone and photosphere.
Determining where and how magnetic fields are generated on
the Sun, and by inference on other stars as well, is a key
goal of astrophysics.
The images used in this study (that can be accessed at the
URL below) reveal small-scale magnetic fields in the area
of a decaying active region. By studying the structure and
motion of these small-scale fields, scientists hope to be
able to differentiate between magnetic structures generated
from sunspot decay and those perhaps generated by a local
dynamo process.
When these images were first seen, Dr. Berger and the team
were surprised to find a variety of magnetic formations
that had not previously been seen on the Sun. Earlier
studies, based on images from smaller telescopes, had led
scientists to believe that small-scale magnetic structure
always took the form of small discrete ‘flux tubes,’ or
individual blobs of magnetic field. However the new images
show surprising ‘ribbon’ and ‘flower’ structures that
indicate much more complex interactions of the small-scale
magnetic field with the granule flowfield.
In addition to the images, the new data includes the
highest resolution magnetogram, or direct measurement of
the density of magnetic fields on the Sun, ever taken. By
combining the images and the magnetogram, Dr. Berger and
the team are measuring the magnetic content of these new
structures for the first time. Further studies of magnetic
flux in quiet Sun regions will be used to compare with the
images shown here in an effort to understand the origin and
fate of small-scale magnetic flux on the Sun.
Preliminary analyses of the data are in a paper submitted
for peer-review to the journal Astronomy &
Astrophysics .The authors are Dr. Tom Berger and Dr. Alan
Title of Lockheed Martin Solar and Astrophysics Lab; Dr.
Luc Rouppe van der Voort, Dr. Mats Carlsson, Dr. Viggo
Hansteen, Astrid Fossum, and Elin Marthinussen of The
Institute for Theoretical Astrophysics, University of Oslo;
and Dr. Goran Scharmer and Dr. Mats Lofdahl of The
Institute for Solar Physics of the Royal Swedish Academy of
Sciences, Stockholm. Future studies will examine movies of
these small-scale structures to determine their dynamical
interactions with granules.
Headquartered in Bethesda, Md., Lockheed Martin is a global
enterprise principally engaged in the research, design,
development, manufacture, and integration of advanced-
technology systems, products, and services. The
Corporation’s core businesses are systems integration,
space, aeronautics, and technology services. Employing
about 125,000 people worldwide, Lockheed Martin had 2002
sales surpassing $26.6 billion.
NOTE TO EDITORS: Low- and high-resolution JPEG image files
of the discovery are available at the following URL:
