Quiet Sun (2009 May 16)

[Axel]

Beautiful picture of the Shuttle and the Hubble Telescope against an almost perfectly bald and smooth Sun - there is a small spot around 7 o'clock from the Shuttle. Is the Sun unusually quiet for this part of its cycle (or not)?

[neufer]

Beautiful picture of the Shuttle and the Hubble Telescope against an almost perfectly bald and smooth Sun - there is a small spot around 7 o'clock from the Shuttle. Is the Sun unusually quiet for this part of its cycle (or not)?

The Sun is unusually quiet for this part of its cycle.

The cycle also began late (as expected):

Scientists Issue Unprecedented Forecast of Next Sunspot Cycle
NCAR News Release March 6, 2006

BOULDER— <<The next sunspot cycle will be 30-50% stronger than the last one and begin as much as a year late, according to a breakthrough forecast using a computer model of solar dynamics developed by scientists at the National Center for Atmospheric Research (NCAR). Predicting the Sun's cycles accurately, years in advance, will help societies plan for active bouts of solar storms, which can slow satellite orbits, disrupt communications, and bring down power systems.

The Predictive Flux-transport Dynamo Model is enabling NCAR scientists to predict that the next solar cycle, known as Cycle 24, will produce sunspots across an area slightly larger than 2.5% of the visible surface of the Sun. The scientists expect the cycle to begin in late 2007 or early 2008, which is about 6 to 12 months later than a cycle would normally start. Cycle 24 is likely to reach its peak about 2012. By analyzing recent solar cycles, the scientists also hope to forecast sunspot activity two solar cycles, or 22 years, into the future. The NCAR team is planning in the next year to issue a forecast of Cycle 25, which will peak in the early 2020s.

The scientists have confidence in the forecast because, in a series of test runs, the newly developed model simulated the strength of the past eight solar cycles with more than 98% accuracy. The forecasts are generated, in part, by tracking the subsurface movements of the sunspot remnants of the previous two solar cycles. The team is publishing its forecast in the current issue of Geophysical Research Letters.

The Sun goes through approximately 11-year cycles, from peak storm activity to quiet and back again. Solar scientists have tracked them for some time without being able to predict their relative intensity or timing. Forecasting the cycle may help society anticipate solar storms, which can disrupt communications and power systems and affect the orbits of satellites. The storms are linked to twisted magnetic fields in the Sun that suddenly snap and release tremendous amounts of energy. They tend to occur near dark regions of concentrated magnetic fields, known as sunspots.

The NCAR team's computer model, known as the Predictive Flux-transport Dynamo Model, draws on research by NCAR scientists indicating that the evolution of sunspots is caused by a current of plasma, or electrified gas, that circulates between the Sun's equator and its poles over a period of 17 to 22 years. This current acts like a conveyor belt of sunspots.

The sunspot process begins with tightly concentrated magnetic field lines in the solar convection zone (the outermost layer of the Sun's interior). The field lines rise to the surface at low latitudes and form bipolar sunspots, which are regions of concentrated magnetic fields. When these sunspots decay, they imprint the moving plasma with a type of magnetic signature. As the plasma nears the poles, it sinks about 200,000 kilometers (124,000 miles) back into the convection zone and starts returning toward the equator at a speed of about one meter (three feet) per second or slower. The increasingly concentrated fields become stretched and twisted by the internal rotation of the Sun as they near the equator, gradually becoming less stable than the surrounding plasma. This eventually causes coiled-up magnetic field lines to rise up, tear through the Sun's surface, and create new sunspots.

The subsurface plasma flow used in the model has been verified with the relatively new technique of helioseismology, based on observations from both NSF– and NASA–supported instruments. This technique tracks sound waves reverberating inside the Sun to reveal details about the interior, much as a doctor might use an ultrasound to see inside a patient.


NCAR scientists have succeeded in simulating the intensity of the sunspot cycle by developing a new computer model of solar processes. This figure compares observations of the past 12 cycles (above) with model results that closely match the sunspot peaks (below). The intensity level is based on the amount of the Sun's visible hemisphere with sunspot activity. The NCAR team predicts the next cycle will be 30-50% more intense than the current cycle. (Figure by Mausumi Dikpati, Peter Gilman, and Giuliana de Toma, NCAR.)>>

[BMAONE23]

Beautiful picture of the Shuttle and the Hubble Telescope against an almost perfectly bald and smooth Sun - there is a small spot around 7 o'clock from the Shuttle. Is the Sun unusually quiet for this part of its cycle (or not)?

Agreeably, the sun is very quiet right now. But it is still very early into te beginning of the next solar cycle. This APOD from MARCH 2002 shows the solar activity after the last Solar Maxima peaked in 2000 While this image shows its current level of activity. It indicates that the solar activity is gradually increasing and we are moving away from this cycles solar minima http://sohowww.nascom.nasa.gov/data/LAT ... it_195.mpg Although none of these would qualify as "SunSpots" (they leave no dark spot on the solar surface) they are areas of dramatically increased magnetic activity on an otherwise quiet stellar body.
The difference between this Solar Maximum image and this Solar Minimum image is readily apparent.

[neufer]

Sunspot activity hits a new low
ABC Wednesday, 8 April 2009 Marilyn Head

<<Astronomers say the sun is experiencing is a very deep solar minimum, but it is still completely within the bounds of what is normal (Source: NASA)

Solar observers are keeping a close eye on the sun as it experiences its quietest period in more than a century. While none are concerned by the lack of sunspots, the 'deep solar minimum' is unique opportunity for astronomers to observe our nearest star.

Dr Sean Oughton, an associate professor of mathematics at New Zealand's Waikato University, says the sun's lack of solar activity is expected. "What we are experiencing is a very deep solar minimum, but it is still completely within the bounds of what is normal," he says.
Flipping out

Oughton says sunspot activity follows 11-year cycles, which are linked to the sun's magnetic field. When the number of sunspots reaches its maximum the polarity of the sun's magnetic field 'flips'.

According to NASA's Space Weather website the sun is in the middle of a solar minimum, with 266 sunspot-free days last year - the lowest for nearly a century. In 2009, the sun has been blemish-free for more than 80 days, putting it on track for an even quieter year.

Record reductions in the solar wind, solar radio emissions and solar brightness have also attracted attention. The reduction in sunspot activity has also seen a drop in solar flares and coronal mass ejections. These events blast vast quantities of atoms and ions into space, disrupting communications systems on earth and threatening astronauts in space.

A drop in solar activity allows more cosmic rays from outer space to enter the solar system. But it's too soon for us to be worried, says Oughton. "The solar wind is in fact so gentle that if you could bottle it up and release it next to a tree, the leaves wouldn't even tremble," he says. Oughton says that even if more cosmic rays enter the solar system, the earth is protected by its own magnetic field.

Past evidence suggests there may be a correlation between sunspot activity and global temperature. A seventy-year cold snap in the seventeenth century, which saw the River Thames freeze over, coincided with a drop in sunspot activity known as the 'Maunder minimum'. While the link seems to be supported by other geological evidence, Oughton says that it is only speculation. He says no mechanism has been found which would prove a connection between minimal sunspot activity and cooler temperatures.

Oughton says the most exciting thing about this unusually quiet period is that it gives scientists like the opportunity to gather more data and fine-tune their predictions. But if it continues, "it could be interesting," he says.>>