Is the solar brightness dependant on how many solarspots

[Max.Planck]

Hello,

I have a question about sunspots, to which the answer i could not find using google. Is the solar brightness dependant on how many solarspots are on the solar surface? I know that sunspots are cooler than the rest of the solar surface, however, the faculas that exist next to solar spots are hotter and therefore brighter.

Can anyone help me with this?

Thanks!

Max Planck

 

[Matterwave]

Sun spots appear to be correlated with Earth's climate...which would suggest to me that perhaps the luminosity is related. For example, during the Maunder minimum where there appeared to be very few sun spots for a period of 60 years or so, the Earth experienced a "little ice age" where temperatures went down quite a bit. It seems that fewer sunspots mean cooler Earth. This correlation is not very well understood.

This whole field is quite poorly understood. You can see this wikipedia article for more: http://en.wikipedia.org/wiki/Maunder_minimum

 

[ViewsofMars]

Hello,

I have a question about sunspots, to which the answer i could not find using google. Is the solar brightness dependant on how many solarspots are on the solar surface? I know that sunspots are cooler than the rest of the solar surface, however, the faculas that exist next to solar spots are hotter and therefore brighter.

Can anyone help me with this?

Thanks!

Max Planck

A warm hello to you, Max. Welcome to Physics Forums. I'm extremely fasinated by your question. I've spent a few hours attempting to do a decent search on the subject matter you provided and did discover:

1. The Solar 'Constant' - Faculae vs. Sunspots
"Three views of the Sun showing different levels of solar activity. The color table has been altered to enhance the appearance of the faculae (white regions) which are hotter than sunspots (red-black regions) and whose greater total area contribute to increasing the solar flux reaching the Earth."
http://svs.gsfc.nasa.gov/vis/a000000/a002600/a002644/index.html


2. Understand variability of the Sun's luminosity"Small variations in the Sun's energy output can change weather and climate on Earth. During the 17th century, an abnormal period of low solar activity conincided with the "Little Ice Age" in northern Europe. Observations from space have shown that the total energy output of the Sun changes with variations in its magnetic cycle.

"Solar-B will continuously monitor the buildup of sunspots as well as extremely small-scale magnetic structures as the Sun heads toward the next peak in its activity cycle."
http://xrt.cfa.harvard.edu/mission/objectives.php

Also, Current Solar Data updated every 30 minutes.
http://xrt.cfa.harvard.edu/missionops/current.php

In response to your question, "Is the solar brightness dependant on how many solarspots are on the solar surface?" My answer would be "no" at this particular time though I am on a mission to explore further. I am going hunting tomorrow for more information.

Have a nice day. Hope you enjoy exploring the websites.

Thank you,
Mars

 

[Astronuc]

Partial answer -

Faculae are bright areas that are usually most easily seen near the limb, or edge, of the solar disk. These are also magnetic areas but the magnetic field is concentrated in much smaller bundles than in sunspots. While the sunspots tend to make the Sun look darker, the faculae make it look brighter. During a sunspot cycle the faculae actually win out over the sunspots and make the Sun appear slightly (about 0.1%) brighter at sunspot maximum that at sunspot minimum.

http://solarscience.msfc.nasa.gov/feature1.shtml

http://solarscience.msfc.nasa.gov/SunspotCycle.shtml

 

[Chronos]

Agreed with Astronuc, the sun is more energetic during peak periods of sunspot activity. The sun's magnetosphere is very active during these times.

 

[ViewsofMars]

Moving onward with my quest for more information about sunspots, etc!

World Book at NASA - Sun
Updated:November 29, 2007
by Editor:Brian Dunbar

I’ve taken a snippet from four categories.

Energy output

Most of the energy emitted (sent out) by the sun is visible light and a related form of radiation known as infrared rays, which we feel as heat. Visible light and infrared rays are two forms of electromagnetic radiation. The sun also emits particle radiation, made up mostly of protons and electrons.

Color

In the visible-light band of the electromagnetic spectrum are all the colors of the rainbow. Sunlight consists of all these colors. Most of the sun's radiation comes to us in the yellow-green part of the visible spectrum. However, sunlight is white. When the atmosphere acts as a filter for the setting sun, the sun may look yellow or orange.

Magnetic field

When the sun's magnetic field becomes complex, field lines resemble a kinked, twisted garden hose. The field develops kinks and twists for two reasons: (1) The sun rotates more rapidly at the equator than at higher latitudes, and (2) the inner parts of the sun rotate more rapidly than the surface. The differences in rotational speed stretch field lines in an easterly direction. Eventually, the lines become so distorted that the kinks and twists develop.

In some areas, the field is thousands of times stronger than the overall magnetic field. In these places, clusters of field lines break through the surface, creating loops in the solar atmosphere. At one end of the loop, the breakthrough point is a magnetic north pole. At this point, the direction of the field lines is upward -- that is, away from the interior. At the other end of the loop, the breakthrough point is a magnetic south pole, and the lines point downward. A sunspot forms at each point. The field lines guide ions and electrons into the space above the sunspots, producing gigantic loops of gas.

The number of sunspots on the sun depends on the amount of distortion in the field. The change in this number, from a minimum to a maximum and back to a minimum, is known as the sunspot cycle. The average period of the sunspot cycle is about 11 years.

At the end of a sunspot cycle, the magnetic field quickly reverses its polarity and loses most of its distortion. Suppose the sun's magnetic north pole and its geographic north pole were at the same place at the start of a given cycle. At the beginning of the next cycle, the magnetic north pole would be at the same place as the geographic south pole. A change of polarity from one orientation to the other and back again equals the periods of two successive sunspot cycles and is therefore about 22 years.

Sunspots

Sunspots are dark, often roughly circular features on the solar surface. They form where denser bundles of magnetic field lines from the solar interior break through the surface.

http://www.nasa.gov/worldbook/sun_worldbook.html

Also, SOHO is a project of international cooperation between ESA and NASA.
Here’s a snippet from an article:

One of the outstanding questions facing solar physicists is the origin of the solar magnetic cycle: What drives the 11-year sunspot cycle? We have just passed an extended and deep minimum, unlike any in the past 100 years. The late onset of the new solar cycle (#24) and the unusually deep minimum between cycles 23 and 24 took all experts by surprise, which suggests that there is a fundamental lack in our understanding of the origin of the solar activity cycle.

The Sun's meridional circulation is a massive flow pattern within the Sun that transports hot plasma near the surface from the solar equator to the poles and back to the equator in the deeper layers of the convection zone, similar to a "conveyor belt". The flow is rather slow, with typical speeds of 10-15 m/s (20 to 30 mph). The structure and strength of this meridional flow is believed to play a key role in determining the strength of the Sun's polar magnetic field, which in turn determines the strength of the sunspot cycles. One class of dynamo models predicts that a stronger meridional flow produces weaker polar fields, whereas another class of models predicts stronger polar fields (and a shorter sunspot cycle) for the same flow.

Analyzing more than 60,000 full disk magnetograms registered by the MDI instrument on SOHO between May 1996 and June 2009, scientist now measured the latitudinal profile of this flow and its variations over a solar cycle by tracking the motions of small-scale magnetic flux concentrations, which are carried away by the meridional flow like leaves on a river. They found an average flow that is poleward at all latitudes up to 75 degrees, which suggests that it extends all the way to the poles. Perhaps even more importantly, they also found that the flow was faster at sunspot cycle minimum than at maximum and substantially faster on the approach to the current minimum than it was at the last solar minimum. This finding poses new constraints on solar dynamo models and may help to explain why the last solar minimum was so peculiar.
http://sohowww.nascom.nasa.gov/hotshots/2010_03_15/

Science had an article worthy of presenting:
Science 12 March 2010:
Vol. 327. no. 5971, pp. 1350 - 1352
DOI: 10.1126/science.1181990

Variations in the Sun’s Meridional Flow over a Solar Cycle
David H. Hathaway1,* and Lisa Rightmire2

Abstract:
The Sun’s meridional flow is an axisymmetric flow that is generally directed from its equator toward its poles at the surface. The structure and strength of the meridional flow determine both the strength of the Sun’s polar magnetic field and the intensity of sunspot cycles. We determine the meridional flow speed of magnetic features on the Sun using data from the Solar and Heliospheric Observatory. The average flow is poleward at all latitudes up to 75°, which suggests that it extends to the poles. It was faster at sunspot cycle minimum than at maximum and substantially faster on the approach to the current minimum than it was at the last solar minimum. This result may help to explain why this solar activity minimum is so peculiar.
http://www.sciencemag.org/cgi/content/abstract/327/5971/1350

 

[ViewsofMars]

A snippet from Earthobservatory- NASA

In 2003, Earth scientists will move a step closer to a full understanding of the Sun’s energy output with the launch of the Solar Radiation and Climate Experiment (SORCE) satellite. SORCE will be equipped with four instruments that will measure variations in solar radiation much more accurately than anything now in use and observe some of the spectral properties of solar radiation for the first time. Robert Cahalan of NASA Goddard Space Flight Center serves as SORCE Project Scientist, and the four instruments are being built at the University of Colorado under the direction of Gary Rottman, SORCE Principal Investigator, with participation by an international team of scientists. SORCE will be launched in January 2003 from Kennedy Space Center on a Pegasus XL launch vehicle provided by Orbital Sciences Corporation. With data from NASA’s SORCE mission, researchers should be able to follow how the Sun affects our climate now and in the future.

Today researchers know that roughly 1,368 watts per square meter (W/m2) of solar energy on average illuminates the outermost atmosphere of the Earth. They know that the Earth absorbs about only 70 percent of this total solar irradiance (TSI), and the rest is reflected into space. Perhaps most intriguing, researchers have affirmed that the TSI doesn’t stay constant, but varies slightly with sunspots and solar weather activity. In particular, by analyzing satellite data, scientists have observed a correlation between the Sun’s output of energy and the 11-year sunspot cycle, which physicists have known of since Galileo’s time. These data show that TSI varies just as regularly as the sunspot activity over this 11-year period, rising and falling 1.4 W/m2 through the course of the cycle (0.1 percent of the TSI). There are also longer-term trends in solar weather activity that last anywhere from years to centuries to millennia and may have an impact on global warming.
http://earthobservatory.nasa.gov/Features/SORCE/sorce.php

Another snippet from an article, Changes in Solar Brightness Too Weak to Explain Global Warming, dated September 13, 2006 peeked my interest.

Brightness variations are the result of changes in the amount of the Sun's surface covered by dark sunspots and by bright points called faculae. The sunspots act as thermal plugs, diverting heat from the solar surface, while the faculae act as thermal leaks, allowing heat from subsurface layers to escape more readily. During times of high solar activity, both the sunspots and faculae increase, but the effect of the faculae dominates, leading to an overall increase in brightness.

The new study looked at observations of solar brightness since 1978 and at indirect measures before then, in order to assess how sunspots and faculae affect the Sun's brightness. Data collected from radiometers on U.S. and European spacecraft show that the Sun is about 0.07 percent brighter in years of peak sunspot activity, such as around 2000, than when spots are rare (as they are now, at the low end of the 11-year solar cycle). Variations of this magnitude are too small to have contributed appreciably to the accelerated global warming observed since the mid-1970s, according to the study, and there is no sign of a net increase in brightness over the period.
http://earthobservatory.nasa.gov/Newsroom/view.php?id=30850

 

[ViewsofMars]

Nature had an article from August 27, 2009 entitled Sunspots stir oceans Variations in the Sun's brightness may have a big role in Pacific precipitation by Geoff Brumfiel.

"Computer simulations are showing how tiny variations in the Sun's brightness can have a big influence on weather above the Pacific Ocean.

"The simulations match observations that show precipitation in the eastern Pacific varies with the Sun's brightness over an 11-year cycle. However, the model does not indicate a relationship between solar activity and the rise in global temperature over the past century.

"This is not a global warming thing," says Gerald Meehl, a modeller at the National Center for Atmospheric Research in Boulder, Colorado, and first author of the study. "But it does indicate that the Sun has a measurable impact on Earth's climate." The research is published this week in the journal Science1.

"Although the Sun burns steadily, its shifting magnetic fields can lead to cooler, darker spots on the Sun's surface. The edges of these sunspots are much brighter than the rest of the Sun, and although this causes only a tiny increase in the Sun's total output of light over the 11-year cycle, researchers believe that it can influence Earth's climate. Many scientists think that a cold snap between 1645 and 1715, for example, may have been caused by an unusually spotless Sun. Researchers had also noticed that precipitation patterns in the Pacific Ocean seemed to vary with the 11-year sunspot cycle, with the average rainfall in the eastern Pacific seeming to drop during periods of high solar activity.

"Solar puzzle

"But how could such a tiny change in brightness influence weather over the world's largest ocean? Two theories have circulated in recent years. The first is that an increase in ultraviolet radiation associated with the brighter Sun changes the temperature of the upper echelons of the atmosphere. Those changes alter the winds over the tropics, and eventually lead to a drought in the east.

"The second theory is that the increased brightness is heating the Pacific itself. The heating intensifies evaporation and rainfall in some regions, but creates cooling winds in the eastern part of the ocean, which prevents rain clouds from forming in those eastern areas.

"Both theories seemed plausible, but when they were inserted separately into the models, neither produced an effect that was big enough to explain the observations, Meehl says. So he and his colleagues tried combining the two into a single model. "Sure enough, we got a much bigger response," he says.

"The work is a good piece of modelling, but not all parts of the puzzle are in place, says Drew Shindell, a climate modeller at the NASA Goddard Institute for Space Studies in New York. Combining the two theories does seem to produce a model that replicates the magnitude of the sunspot cycle's impact. But the results of the simulation are far from being a perfect geographical match for real observations (see 'A model forecast'). "I think it's a nice step," Shindell says. "But there's clearly still a long way to go."

""I don't think we're claiming we've solved the problem," Meehl says. But he maintains that the model clearly replicates the general trends seen in the Pacific. He expects that as atmospheric scientists, oceanographers and others combine their different models in the coming years, their predictive power will only improve."

http://www.nature.com/news/2009/090827/full/news.2009.869.html#B1

 

[Max.Planck]

Thank you so much for all your support guys!