This from the this month’s meeting of the American Astronomical Society’s Solar Physics Division.
ASA Science News for March 1, 2013
Something unexpected is happening on the sun. 2013 is supposed to be the year of Solar Max, but solar activity is lower than expected. At least one leading forecaster expects the sun to rebound with a double-peaked maximum later this year.
FULL STORY: http://science.nasa.gov/science-news/science-at-nasa/2013/01mar_twinpeaks/
Remember all that data analysis you’ve been doing at www.solarstormwatch.com? All those storms you’ve tracked have now been used to create an animation of what the Sun has been up to over the first three years of the STEREO mission. It’s amazing! You can now see the constant stream of solar wind material as it erupts into space and even the spirals created as the various sources of solar wind rotate with the Sun. And when a solar storm erupts, you can see which planets are in the firing line! Watch the video and read more on the blog at http://blog.solarstormwatch.com/2012/12/19/see-your-data-analysis-like-never-before/
In other news, the BBC are making a documentary about the Sun and would like to feature Solar Stormwatch, including a small group of volunteers. They will be filming at Rutherford Appleton Laboratories in Oxfordshire in the UK (http://www.stfc.ac.uk/About+STFC/51.aspx). Filming is going to take place either February 28 or March 1 2013 (date to be confirmed).
If you are a UK-based Solar Stormwatch volunteer and would like to be part of the documentary please email email@example.com with the subject heading ‘SSW Documentary’ and we’ll forward your message on to the BBC. Unfortunately the BBC cannot pay travel expenses but if you can get to RAL they guarantee a good day out! There is more information on the Solar Stormwatch blog: http://blog.solarstormwatch.com/2013/02/04/calling-all-stormwatchers-bbc-2-documentary-needs-your-help/
This is a great opportunity to promote Solar Stormwatch and get even more involved in solar science.
Jan. 8, 2013: In the galactic scheme of things, the Sun is a remarkably constant star. While some stars exhibit dramatic pulsations, wildly yo-yoing in size and brightness, and sometimes even exploding, the luminosity of our own sun varies a measly 0.1% over the course of the 11-year solar cycle.
There is, however, a dawning realization among researchers that even these apparently tiny variations can have a significant effect on terrestrial climate. A new report issued by the National Research Council (NRC), “The Effects of Solar Variability on Earth’s Climate,” lays out some of the surprisingly complex ways that solar activity can make itself felt on our planet.
Understanding the sun-climate connection requires a breadth of expertise in fields such as plasma physics, solar activity, atmospheric chemistry and fluid dynamics, energetic particle physics, and even terrestrial history. No single researcher has the full range of knowledge required to solve the problem. To make progress, the NRC had to assemble dozens of experts from many fields at a single workshop. The report summarizes their combined efforts to frame the problem in a truly multi-disciplinary context.
One of the participants, Greg Kopp of the Laboratory for Atmospheric and Space Physics at the University of Colorado, pointed out that while the variations in luminosity over the 11-year solar cycle amount to only a tenth of a percent of the sun’s total output, such a small fraction is still important. “Even typical short term variations of 0.1% in incident irradiance exceed all other energy sources (such as natural radioactivity in Earth’s core) combined,” he says.
Of particular importance is the sun’s extreme ultraviolet (EUV) radiation, which peaks during the years around solar maximum. Within the relatively narrow band of EUV wavelengths, the sun’s output varies not by a minuscule 0.1%, but by whopping factors of 10 or more. This can strongly affect the chemistry and thermal structure of the upper atmosphere.
Several researchers discussed how changes in the upper atmosphere can trickle down to Earth’s surface. There are many “top-down” pathways for the sun’s influence. For instance, Charles Jackman of the Goddard Space Flight Center described how nitrogen oxides (NOx) created by solar energetic particles and cosmic rays in the stratosphere could reduce ozone levels by a few percent. Because ozone absorbs UV radiation, less ozone means that more UV rays from the sun would reach Earth’s surface.
Isaac Held of NOAA took this one step further. He described how loss of ozone in the stratosphere could alter the dynamics of the atmosphere below it. “The cooling of the polar stratosphere associated with loss of ozone increases the horizontal temperature gradient near the tropopause,” he explains. “This alters the flux of angular momentum by mid-latitude eddies. [Angular momentum is important because] the angular momentum budget of the troposphere controls the surface westerlies.” In other words, solar activity felt in the upper atmosphere can, through a complicated series of influences, push surface storm tracks off course.
Many of the mechanisms proposed at the workshop had a Rube Goldberg-like quality. They relied on multi-step interactions between multiples layers of atmosphere and ocean, some relying on chemistry to get their work done, others leaning on thermodynamics or fluid physics. But just because something is complicated doesn’t mean it’s not real.
Indeed, Gerald Meehl of the National Center for Atmospheric Research (NCAR) presented persuasive evidence that solar variability is leaving an imprint on climate, especially in the Pacific. According to the report, when researchers look at sea surface temperature data during sunspot peak years, the tropical Pacific shows a pronounced La Nina-like pattern, with a cooling of almost 1o C in the equatorial eastern Pacific. In addition, “there are signs of enhanced precipitation in the Pacific ITCZ (Inter-Tropical Convergence Zone ) and SPCZ (South Pacific Convergence Zone) as well as above-normal sea-level pressure in the mid-latitude North and South Pacific,” correlated with peaks in the sunspot cycle.
The solar cycle signals are so strong in the Pacific, that Meehl and colleagues have begun to wonder if something in the Pacific climate system is acting to amplify them. “One of the mysteries regarding Earth’s climate system … is how the relatively small fluctuations of the 11-year solar cycle can produce the magnitude of the observed climate signals in the tropical Pacific.” Using supercomputer models of climate, they show that not only “top-down” but also “bottom-up” mechanisms involving atmosphere-ocean interactions are required to amplify solar forcing at the surface of the Pacific.
In recent years, researchers have considered the possibility that the sun plays a role in global warming. After all, the sun is the main source of heat for our planet. The NRC report suggests, however, that the influence of solar variability is more regional than global. The Pacific region is only one example.
Caspar Amman of NCAR noted in the report that “When Earth’s radiative balance is altered, as in the case of a chance in solar cycle forcing, not all locations are affected equally. The equatorial central Pacific is generally cooler, the runoff from rivers in Peru is reduced, and drier conditions affect the western USA.”
Raymond Bradley of UMass, who has studied historical records of solar activity imprinted by radioisotopes in tree rings and ice cores, says that regional rainfall seems to be more affected than temperature. “If there is indeed a solar effect on climate, it is manifested by changes in general circulation rather than in a direct temperature signal.” This fits in with the conclusion of the IPCC and previous NRC reports that solar variability is NOT the cause of global warming over the last 50 years.
Much has been made of the probable connection between the Maunder Minimum, a 70-year deficit of sunspots in the late 17th-early 18th century, and the coldest part of the Little Ice Age, during which Europe and North America were subjected to bitterly cold winters. The mechanism for that regional cooling could have been a drop in the sun’s EUV output; this is, however, speculative.
Dan Lubin of the Scripps Institution of Oceanography pointed out the value of looking at sun-like stars elsewhere in the Milky Way to determine the frequency of similar grand minima. “Early estimates of grand minimum frequency in solar-type stars ranged from 10% to 30%, implying the sun’s influence could be overpowering. More recent studies using data from Hipparcos (a European Space Agency astrometry satellite) and properly accounting for the metallicity of the stars, place the estimate in the range of less than 3%.” This is not a large number, but it is significant.
Indeed, the sun could be on the threshold of a mini-Maunder event right now. Ongoing Solar Cycle 24 is the weakest in more than 50 years. Moreover, there is (controversial) evidence of a long-term weakening trend in the magnetic field strength of sunspots. Matt Penn and William Livingston of the National Solar Observatory predict that by the time Solar Cycle 25 arrives, magnetic fields on the sun will be so weak that few if any sunspots will be formed. Independent lines of research involving helioseismology and surface polar fields tend to support their conclusion. (Note: Penn and Livingston were not participants at the NRC workshop.)
“If the sun really is entering an unfamiliar phase of the solar cycle, then we must redouble our efforts to understand the sun-climate link,” notes Lika Guhathakurta of NASA’s Living with a Star Program, which helped fund the NRC study. “The report offers some good ideas for how to get started.”
In a concluding panel discussion, the researchers identified a number of possible next steps. Foremost among them was the deployment of a radiometric imager. Devices currently used to measure total solar irradiance (TSI) reduce the entire sun to a single number: the total luminosity summed over all latitudes, longitudes, and wavelengths. This integrated value becomes a solitary point in a time series tracking the sun’s output.
In fact, as Peter Foukal of Heliophysics, Inc., pointed out, the situation is more complex. The sun is not a featureless ball of uniform luminosity. Instead, the solar disk is dotted by the dark cores of sunspots and splashed with bright magnetic froth known as faculae. Radiometric imaging would, essentially, map the surface of the sun and reveal the contributions of each to the sun’s luminosity. Of particular interest are the faculae. While dark sunspots tend to vanish during solar minima, the bright faculae do not. This may be why paleoclimate records of sun-sensitive isotopes C-14 and Be-10 show a faint 11-year cycle at work even during the Maunder Minimum. A radiometric imager, deployed on some future space observatory, would allow researchers to develop the understanding they need to project the sun-climate link into a future of prolonged spotlessness.
Some attendees stressed the need to put sun-climate data in standard formats and make them widely available for multidisciplinary study. Because the mechanisms for the sun’s influence on climate are complicated, researchers from many fields will have to work together to successfully model them and compare competing results. Continued and improved collaboration between NASA, NOAA and the NSF are keys to this process.
Hal Maring, a climate scientist at NASA headquarters who has studied the report, notes that “lots of interesting possibilities were suggested by the panelists. However, few, if any, have been quantified to the point that we can definitively assess their impact on climate.” Hardening the possibilities into concrete, physically-complete models is a key challenge for the researchers.
Finally, many participants noted the difficulty in deciphering the sun-climate link from paleoclimate records such as tree rings and ice cores. Variations in Earth’s magnetic field and atmospheric circulation can affect the deposition of radioisotopes far more than actual solar activity. A better long-term record of the sun’s irradiance might be encoded in the rocks and sediments of the Moon or Mars. Studying other worlds might hold the key to our own.
The full report, “The Effects of Solar Variability on Earth’s Climate,” is available from the National Academies Press at http://www.nap.edu/catalog.php?record_id=13519.
Author: Dr. Tony Phillips |Production editor: Dr. Tony Phillips | Credit: Science@NASA
Article note sent by Solar observer Raymond Rienks
INCOMING CMES: A pair of minor CMEs is heading for Earth. They were
launched on Nov. 9th and 10th, respectively, and are expected to merge
into a single cloud before they reach our planet on Nov. 12th.
NOAA forecasters estimate a 55% chance of polar geomagnetic storms
in the next 48 hours.
Prepared jointly by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center and the U.S. Air Force. Updated 2012 Jul 26 2200 UTC Joint USAF/NOAA Report of Solar and Geophysical Activity SDF Number 208 Issued at 2200Z on 26 Jul 2012 IA. Analysis of Solar Active Regions and Activity from 25/2100Z to 26/2100Z: Solar activity was low. The only C-class flare of the reporting period was a C1 at 26/1953Z from new Region 1532 (S20E67). New flux emergence was observed in the northwest quadrant and was numbered as Region 1531 (N15W59). IB. Solar Activity Forecast: Solar activity is expected to be very low with a chance for a C-class flare. IIA. Geophysical Activity Summary 25/2100Z to 26/2100Z: The geomagnetic field was quiet. The greater than 10 MeV proton event at geosynchronous orbit that began at 23/1545Z, reached a maximum flux of 12 pfu at 23/2145Z and ended at 24/1800Z. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels during the period. IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be quiet on day 1 (27 July). By mid to late on day 2 (28 July), a recurrent coronal hole high speed stream (CH HSS) is expected to become geoeffective causing unsettled to active periods. Unsettled to active periods are expected on day 3 (29 July) due to the combined effects of the CH HSS and the 25 July coronal mass ejection. III. Event Probabilities 27 Jul-29 Jul Class M 05/05/05 Class X 01/01/01 Proton 01/01/01 PCAF Green IV. Penticton 10.7 cm Flux Observed 26 Jul 115 Predicted 27 Jul-29 Jul 115/115/120 90 Day Mean 26 Jul 125 V. Geomagnetic A Indices Observed Afr/Ap 25 Jul 006/007 Estimated Afr/Ap 26 Jul 000/004 Predicted Afr/Ap 27 Jul-29 Jul 006/005-011/015-015/018 VI. Geomagnetic Activity Probabilities 27 Jul-29 Jul A. Middle Latitudes Active 05/25/35 Minor storm 01/10/20 Major-severe storm 01/01/05 B. High Latitudes Active 15/15/10 Minor storm 10/25/30 Major-severe storm 05/30/50
Space Weather News for July 12, 2012
EARTH-DIRECTED X-FLARE: Big sunspot AR1520 erupted on July 12th around 16:53 UT, producing an X-class solar flare and hurling a CME directly toward Earth. Forecasters expect the cloud to arrive on July 14th. Its impact could spark moderate to severe geomagnetic storms, allowing auroras to be seen at lower latitudes than usual. Check http://spaceweather.com for more information and updates.
Space Weather News for March 9, 2012
INCOMING CME: As Earth’s magnetic field reverberates from the impact of one CME on March 8th, a second CME is on the way. Big sunspot AR1429 unleashed an M6-class solar flare today, and the eruption hurled a cloud of plasma almost directly toward Earth. Forecasters say the CME could reach our planet during the late hours of March 10th or early hours of March 11th. Strong geomagnetic storms are possible when the cloud arrives. Check http://spaceweather.com for more information and updates.
CR2119 has been released.
Look under the Pages Section A.L.P.O. Solar Section Recent Observations.
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