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GEOMAGNETIC
STORM WARNING: A pair of closely-spaced
CMEs propelled by explosions of sunspot AR1302 on
Sept. 24th are heading not-quite directly toward
Earth. A significant glancing blow to our planet's
magnetic field is possible on Sept. 26th around
14:00 UT (+/- 7 hours). NOAA forecasters estimate
a 30% chance of strong geomagnetic storms when the
clouds arrive. [CME
forecast track]
Aurora alerts: text,
voice.
STRONG
SOLAR ACTIVITY: Having already
unleashed two X-flares since Sept. 22nd, sunspot
AR1302 appears ready for more. The active region
has a complex "beta-gamma-delta" magnetic
field that harbors energy for strong M-
and X-class eruptions. Flares from AR1302 will
become increasingly geoeffective as the sunspot
turns toward Earth in the days ahead.
Marko Posavec of Koprivnica, Croatia,
photographed the behemoth sunspot between flares
on Sept. 24th:
Photo details: Olympus E-510, Sigma
50-500mm lens (at 500mm), 1/640 sec. exposure, f/18,
ISO 100
"Sunspot complex 1302 is incredibly
easy to spot at sunrise or sunset," says Posavec.
"Be careful, though. Even the low-hanging sun
is bright enough to damage your eyes if you look
at it through optics of any kind." Safe solar
filters may be found in the SpaceWeather
Store.
more images: from
Alan Friedman of Buffalo, NY; from
Monika Landy-Gyebnar of Balatonfured, Hungary;
from
Piet Berger of Simpelveld, Netherlands; from
Howard Eskildsen of Ocala, Florida; from
Dzmitry Kananovich of Tallinn, Estonia; from
Chris Schur of Payson, Az; from
John Stetson of Falmouth, Maine; from
Grenier of Paris France; from
Maximilian Teodorescu of Magurele, Romania;
from
Cai-Uso Wohler of Bispingen, Germany; from
Philippe Van den Doorn of Rixensart, Belgium
SOLAR
STATIC: Active sunspot 1302 has
turned the sun into a shortwave radio transmitter.
Shock waves rippling from the sunspot's exploding
magnetic canopy excite plasma oscillations in the
sun's atmosphere. The result is bursts of static
that may be heard in the loudspeakers of shortwave
radios on Earth. Amateur radio astronomer Thomas
Ashcraft recorded this
sample from his backyard observatory in New
Mexico on Sept. 24th:
Dynamic spectrum: The horizontal
axis is time (h:m:s), the vertical axis is frequency
(MHz). Image credit: Wes Greenman
"Saturday was a super-strong
solar day with near continuous flaring and radio
sweeps," says Ashcraft. "The sound file
(above) corresponds to an M3 flare at 1918 UTC.
It was the strongest radio sweep of the observing
day."
"Try listening to the radio bursts
in stereo," he advises. "I was recording
on two separate radios at 21.1 MHz and 21.9 MHz,
and I put each one into its own channel of the audio
file. This gives a spatial dimension as the bursts
sweep down in frequency."
September
2011 Aurora Gallery
[previous Septembers: 2010,
2009, 2008,
2007,
2006,
2005,
2004]
