SONOGRAMS OF THE SUN EXPLAIN MYSTERY OF THE MISSING SUNSPOTS

Here is visual backup material for the AAS/SPD press conference of the same name; at the bottom is a copy of the initial press release. This page will remain accessible until 1-July-2009. Each web-sized image is a hyperlink to a higher-resolution copy of itself.

For access to the telecon, you may dial 866-606-4698 or +1-713-577-1201; the access code is 7976073.


Principal visuals

1. solar diagram

This diagram of the Sun's internal structure shows the Sun's major parts, including the jet streams that are the subject of today's telecon. The jet streams extend deep into the Sun, to the base of the solar convective zone.

2. Solar movie

(click image for movie) This movie reveals motions of the Sun's interior as measured with helioseismology on data from GONG and SOHO/MDI. East to west motion is color coded: blue is slow, red is fast. A red band in the outer third of the Sun moves slowly down from near each pole toward the equator; that band is the jet stream that is associated with sunpot emergence and the solar cycle. As of early 2009 the Cycle 24 jet streams have just reached N/S 22 degrees latitude, and new sunspots are beginning to emerge.

3. 7000 km down

This diagram shows east-to-west motion speed versus latitude, as it evolves year to year at a depth of 4000 miles (7000 km) in the solar interior, as derived from helioseismology observations by GONG and SOHO?MDI. The diagonal yellow bands are the "torsional oscillation" jet streams inside the Sun. The streams are associated with the solar activity cycle. The flow for the previous cycle (#23) can be seen in yellow at the left side of the picture, while the flow for the next cycle (#24) is visible in yellow at the right side of the image. The streams for Cycle 24 have migrated slower than those for Cycle 23. The bottom of the yellow band is currently at the critical latitude of N/S 22 degrees (mid 2009).

4. 7000 km deep overlay

This diagram shows east-to-west motion like (2) above, but overlain on the surface pattern of sunspots and solar activity high above. The dashed diagonal lines show the slope (in degrees of latitude per year) of the Cycle 23 motion. The Cycle 24 motion has a shallower slope, requiring one extra year compared to Cycle 23 to reach the critical latitude of 22 degrees. The Cycle 24 stream is just now reaching the critical latitude, and faint signs of sunspot activity can be seen in the northern hemisphere at right. This heralds the start of a new solar cycle.


Backup visuals

Solar Image

A visible light image of the active Sun. Sunspots emerge in a pair of narrow latitude bands associated with the "torsional oscillation" jet streams. When the streams, marching toward the equator, reach 22 degrees latitude, new sunspots begin to appear.

Butterfly Diagram

This "butterfly diagram" shows number and position of sunspots for many solar cycles. The current long minimum is unusual but not unprecedented. The new solar cycle (#24) is just beginning to appear at far right.



June 16, 2009

Contact:
Craig DeForest
AAS/SPD Press Officer
+1 303-641-5769

AAS/SPD PRESS CONFERENCE, WEDNESDAY, JUNE 17, 2009:
SONOGRAMS OF THE SUN EXPLAIN MYSTERY OF THE MISSING SUNSPOTS

EDITORS: Please do not post or publish the information on
press-conference access for journalists. **Please note the embargo for
12:30 p.m. MDT, Wednesday, June 17, 2009.**

Below is a press release that relates to the press conference "New
Insight into the Sun's Mysterious Quiet Period" at 12:30 p.m. MDT
(2:30 p.m. EDT) on Wednesday, June 17, 2009, at the triennial
standalone meeting of the Solar Physics Division of the American
Astronomical Society in Boulder, Colorado. Also included is
information on how off-site reporters can participate in the briefing
via telephone and/or Internet.

PRESS CONFERENCE ACCESS FOR JOURNALISTS

Audio Conference Call:
Toll-free calls (from within the U.S.), dial 1-866-606-4698
International calls, e-mail deforest@boulder.swri.edu for access
When prompted, enter passcode 7976073

Internet Audio/Visual access:
Point your web browser to http://spd.boulder.swri.edu/solar_mystery
for access to visual material that will be used during the press
conference. (The content will be made available at 12:00 pm MDT,
Wednesday, June 17, 2009.)

To ask questions during the conference call, please wait until
prompted by the chair of the briefing, or (to ensure that your
question will be taken) e-mail it to deforest@boulder.swri.edu during
the briefing.

The press conference will not be archived.

PRESS RELEASE

Forwarding of the following release does not imply endorsement by the
American Astronomical Society.

EMBARGOED UNTIL:
12:30 .m. MDT (2:30 p.m. EDT)
Wednesday, June 17, 2009

Press contact:
Dr. Craig DeForest
SPD Press Officer
deforest@boulder.swri.edu
+1 303-641-5769

Scientific contacts:
Dr. Frank Hill
National Solar Observatory
hill@noao.edu
+1 520-318-8138

Dr. Rachel Howe
National Solar Observatory
rhowe@noao.edu
+1 520-318-8573

Dr. Dean Pesnell
NASA/GSFC
William.D.Pesnell@nasa.gov
+1 301-286-4009

SONOGRAMS OF THE SUN EXPLAIN MYSTERY OF THE MISSING SUNSPOTS

Boulder, Colorado -- Scientists from the National Solar Observatory
(NSO) in Tucson, Arizona, have discovered that a solar jet stream deep
inside the Sun is migrating slower than usual through the star's
interior, giving rise to the current lack of sunspots and low solar
activity, according to work being presented this week at the meeting
of the Solar Physics Division of the American Astronomical Society
(AAS/SPD).

The Sun normally undergoes an eleven-year cycle of magnetic activity
related to sunspots, solar flares, and the interplanetary storms
called "CMEs". The current "solar minimum" quiet period has been
unusually long and deep, confounding scientists who hope to understand
the origins of space weather and the Sun's magnetic field.

Drs. Rachel Howe and Frank Hill, both of the NSO, used long-term
observations from the NSO's Global Oscillation Network Group (GONG)
facility to detect and track an east-to-west jet stream, known as the
"torsional oscillation", at depths of ~1,000 to 7,000 km below the
surface of the Sun. The Sun generates new jet streams near its poles
every 11 years; the streams migrate slowly, over a period of 17 years,
to the equator, and are associated with the production of sunspots
once they reach a critical latitude of 22 degrees.

Howe and Hill found that the stream associated with the new solar
cycle has moved sluggishly, taking three years to cover a 10 degree
range in latitude compared to two years for the last solar cycle, but
has now reached the critical latitude. The current solar minimum has
become so long and deep, some scientists have speculated the Sun might
enter a long period with no sunspot activity at all. The new result
both shows that the Sun's internal magnetic dynamo continues to
operate, and heralds the beginning of a new cycle of solar activity.

"It is exciting to see", said Dr. Hill, "that just as this sluggish
stream reaches the usual active latitude of 22 degrees, a year late,
we finally begin to see new groups of sunspots emerging at the new
active latitude." 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.

GONG and its sister instrument SOHO/MDI measure sound waves on the
surface of the Sun. Scientists can then use the sound waves to probe
structures deep in the interior of the star, in a process analogous to
a sonogram in a medical office. "Using the global sound wave
inversions, we have been able to reveal the intimate connection
between subtle changes in the Sun's interior and the sunspot cycle on
its surface," said Hill.

"This is an important piece of the solar activity puzzle," said Dr.
Dean Pesnell, of NASA's Goddard Space Flight Center. "It shows how
flows inside the Sun are related to the creation of solar activity and
how the timing of the solar cycle might be produced. None of the
forecasting research groups predicted the current long extended delay
in the new cycle. There is a lot more to learn in order to understand
how the Sun creates magnetic fields."

The new science of helioseismology, enabled by instruments such as the
ground- based GONG, the Michelson Doppler Imager aboard the SOHO
spacecraft, and NASA's planned Solar Dynamics Observatory, has
revolutionized understanding of the solar interior. "While the surface
effects of the Sun's torsional oscillations have been observed for
some time, understanding of the dynamo and the origin of sunspots
depend on measurements of the solar interior that are only possible
with helioseismic techniques", said Hill.

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An additional science contact named in the conference was:
Jesper Schou, Stanford University
650-725-9826
schou@quake.stanford.edu