American Astronomical Society Meeting
Highlights from the 220th AAS meeting held June 10-14 in Anchorage, Alaska
By Nadia Drake
20 hours of fame
Seen in gamma rays, the sun is usually dark. But on March 7, it blazed for 20 hours after a massive solar flare dumped high-energy particles and light into space. “The sky looked completely different,” Stanford University’s Nicola Omodei said on June 11. NASA’s Fermi Gamma-Ray Space Telescope captured the sun’s brief moment in the … sun, and recorded “the highest-energy light ever detected during a solar flare,” Omodei said. Scientists studying the gamma-ray–producing particles determined that instead of only being flung outward by the initial flare-producing shock, the particles were probably also accelerated by reconnecting solar magnetic fields after the event.
Sun’s short-term memory
Scientists trying to forecast peaks in solar cycle activity have generated vastly variable estimates, ranging from Wimpy to Hulk. Dibyendu Nandy, from the Indian Institute of Science Education and Research in Kolkata, suggests an explanation for the prognostic failure. “The sun has a very short memory,” he said on June 11. “It forgets its history of past activity.” That’s because a process called “turbulent pumping” mixes the solar magnetic field and erases “memories” of past cycles of activity. This mixing makes previous solar cycles bad indicators of future intensity. Instead, Nandy suggests that solar maximums, or periods when the sun has its highest number of sunspots, can be reliably predicted only using the previous minimum — which means the sun remembers its own history for just 5.5 years.