When is the best time to see auroras? Where is the best place to go? And how do you photograph them? These questions and more are answered in a new book, Northern Lights - a Guide, by Pal Brekke & Fredrik Broms.
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CHANCE OF FLARES: NOAA forecasters estimate a 50% chance of X-class solar flares and an 80% chance of M-class solar flares today. The source would be active sunspot AR1748, which is turning toward Earth. Solar flare alerts: text, voice.
ANOTHER X-FLARE ON MAY 15: When the week began, the sun hadn't unleashed an X-flare all year long. In only two days, sunspot AR1748 has produced four. The latest X-flare from this active sunspot occured on May 15th at 0152 UT. NASA's Solar Dynamics Observatory captured the extreme ultraviolet flash:
Although the sunspot is not directly facing Earth, this flare might have produced a CME with an Earth-directed component. We are waiting for coronagraph data from SOHO and the twin STEREO probes to check this possibility. Stay tuned for updates.
In summary, AR1748 has produced an X1.7-class flare (0217 UT on May 13), an X2.8-class flare (1609 UT on May 13), an X3.2-class flare (0117 UT on May 14), and an X1-class flare (0152 on May 15). These are the strongest flares of the year, and they signal a significant increase in solar activity. Solar flare alerts: text, voice.
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ION WAVES IN THE ATMOSPHERE: Although AR1748 is not directly facing Earth, its strong flares have nevertheless affected our atmosphere. UV and X-radiation hitting the top of the atmosphere ionizes atoms and molecules, creating ion waves over the dayside of the planet. Roberto Battaiola detected these waves on May 13th using a Sudden Ionospheric Disturbance monitor in Milan, Italy:
Sudden ionospheric disturbances--"SIDs" for short--make themselves known by the effect they have on low-frequency radio signals. When a SID passes by, the atmosphere overhead becomes an good reflector for radio waves, allowing signals to be received from distant transmitters. Battaiola monitored a faraway 21.75 kHz radio station to monitor the SIDs over his location.
More SIDS are in the offing as NOAA forecasters estimate an 80% chance of M-flares and a 50% chance of X-flares during the next 24 hours. Solar flare alerts: text, voice.
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[previous years: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2011]