overview of projects throughout the organization
This image from the Solar Optical Telescope, which was built for the Hinode satellite by a U.S.-Japanese consortium that includes NCAR, shows narrow features called spicules streaming outward from the solar surface during the Quiet Sun Characterization Campaign this spring. Scientists are trying to determine how the various types of spicules form and how they relate to solar energy transfer. Click here to see an animation. (Image and animation courtesy Scott McIntosh.)
Is the “quiet Sun” a misnomer? The Sun is currently in the minimum of its 11-year cycle, with sunspot counts and other signs of activity as low as scientists have observed in the last 50 years. But this doesn’t mean all is calm. Scott McIntosh (ESSL/HAO) and colleagues believe the phrase “quiet Sun”—a name given to portions of the solar atmosphere away from sunspots—doesn’t adequately describe what is going on in the baseline state of solar activity.
At the spring meeting of the American Geophysical Union, Scott presented initial results from the Quiet Sun Characterization Campaign, which took place April 10–16 as part of the International Heliophysical Year. The goal was to analyze the coupling between the Sun’s dynamic lower atmosphere and corona, assess the flow of energy through an intervening region, and compare results from this solar minimum and the last one. “Our observations may help shed more light on not only chromospheric and coronal heating at solar minimum but also the origins of the fast solar wind,” Scott says.
Scott and colleagues drew on high-resolution data from a wide variety of multiwavelength instruments, including several aboard the Hinode satellite. As expected, they found very low levels of activity in the corona, but the atmosphere just below was a place of constant evolution and was far from quiet. There, the team found a multitude of colorfully named phenomena, including spicules, jets, shocks, surges, macrospicules, and blinkers.
All of these are now being linked to the relentless evolution of magnetic fields in the plasma near the Sun’s surface, says Scott. “We saw that there is nowhere on the Sun that you can label truly quiet—just areas that display different degrees of activity. Understanding these is allowing us to slowly navigate one of the final frontiers in solar research.”
Plants and aspirin. Scientists working on TIIMES’s BEACHON study last year in a walnut grove in California (the same site as CHATS) were surprised to measure methylsalicylate being emitted from plants. Methylsalicylate, a plant hormone, is a volatile form of aspirin.
Plants release the chemical when they are under stress from various biological factors, such as large temperature swings or pest infestations. Until now, scientists believed that the chemical was emitted in such small quantities that it couldn’t be measured in the atmosphere and didn’t play an important role in atmospheric chemistry.
“The main thing we are excited about is that nobody has observed this before in the real atmosphere,” says Thomas Karl (ESSL/ACD), adding that researchers have documented the process in lab studies. “From our measurements we see methylsalicylate can be emitted in significant quantities.”
Thomas, along with Alex Guenther, Andrew Turnipseed, Ned Patton, and Kolby Jardine, published the findings online in Biogeosciences on June 6.
The chemical serves as a signal between plants. When a stressed plant emits methylsalicylate, nearby plants take it up and convert it to salicylic acid, a closely related substance to aspirin (acetylsalicylic acid). This in turn activates defense mechanisms in those plants—for example, producing chemicals that are toxic to an invader. During CHATS, the stressor was likely drought combined with large temperature swings between night and day, which can damage plant membranes.
Methylsalicylate emitted by plants could affect atmospheric chemistry by impacting the formation of secondary organic aerosols, which have implications for climate. In addition, because stressed plants emit methylsalicylate before visual damage is apparent, the research may give scientists an early warning signal for detecting damage to ecosystems.
“If we’re able to measure the chemicals on a large scale in the atmosphere, we’ll have a chemical marker for stress which, combined with ecosystem health studies, might provide a chemical way to diagnose the health of plants,” Thomas says.
For more about BEACHON (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen) visit www.tiimes.ucar.edu/beachon.