The Sun's a hot topic

David Hosansky, NCAR & UCAR Media Relations  |  21 September 2009  •  The Sun is in one of its quietest periods in the last century, as noted in a NASA summary issued on 3 September and a recent article in the NCAR/UCAR Staff Notes newsletter. However, solar researchers at NCAR and elsewhere are in high gear.

The public is keenly interested in the Sun and its doings.  “Sunspots” is one of the most frequent search terms bringing visitors to the NCAR/UCAR website. In our media office, we’ve seen an almost unprecedented amount of news regarding the Sun in recent months. Some examples:

Sunspot simulationThe interface between a sunspot's umbra (dark center) and penumbra (lighter outer region) shows a complex structure with narrow, almost horizontal (lighter to white) filaments embedded in a background having a more vertical (darker to black) magnetic field. Farther out, extended patches of horizontal field dominate. For the first time, NCAR scientists and colleagues have modeled this complex structure in a comprehensive 3D computer simulation, giving scientists their first glimpse below the visible surface to understand the underlying physical processes. (Image courtesy Matthias Rempel, NCAR.  See more images and video animations in the Sunspots Multimedia Gallery.)

  • An international team featuring scientists from NCAR and the Max Planck Institute for Solar System Research has created the first-ever comprehensive computer model of sunspots. The results, which were covered in publications as diverse as Wired and LiveScience.com and featured in an exhibit at the Hayden Planetarium of the American Museum of Natural History, capture both scientific detail and remarkable beauty.  At right is one example of this imagery.
     
  • NCAR scientist Gerald Meehl led two major studies—one in Science in August and the other in the Journal of Climate in July—about the solar cycle driving weather events on Earth that are similar to El Niño and La Niña. The Sun’s impact on these events is magnified by chemical reactions in the stratosphere as well as the warming of surface waters in the tropical Pacific. Participants in this research came from NCAR and the Free University of Berlin.
     
  • A study just published in September by NCAR’s Sarah Gibson and colleagues  finds that sunspots tell only part of the story. Even when the Sun reaches minimum in the 11-year cycle and there are virtually no sunspots, Earth can still be bombarded with high-speed streams of charged particles that can disrupt satellites and threaten astronauts while generating impressive auroral displays. Gibson conducted the study with scientists from NCAR, the University of Michigan, NOAA, and NASA.

Such research to help us better understand the solar cycle and its impacts on Earth may eventually lead the way to predicting these powerful geomagnetic storms.

Is the Sun warming our climate?

One question we're asked and see frequently elsewhere is whether the Sun may be responsible for global warming. Even when scientists include variations in solar output in computer models simulating recent climate—especially the rapid warming of the late twentieth century—they find the warming is caused primarily by emissions of carbon dioxide and other greenhouse gases. In fact, the Intergovernmental Panel on Climate Change concluded in 2007 that the combination of solar variations and volcanic eruptions likely had a cooling effect on Earth’s climate over the last 50 years (see page 5 of the Summary for Policymakers in the IPCC’s 2007 synthesis report).

While the recent research gives us new insights into the Sun, it does not alter the basic physics of climate change.