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GEOMAGNETIC STORM: A CME hit Earth's
magnetic field on May 18th at around 0100 UT. Although
it was just a glancing blow, the impact was enough
to spark a G1-class geomagnetic storm. In the United
States, Northern Lights descended as far south as
Pawnee Buttes, Colorado:
"The aurora was not visible to
the naked eye," says photographer Robert Arn.
"Only with a 30 second exposure did I know
it was there. As I started to collect data, I noticed
an electrical storm in the distance. The juxtaposition
of the electrical storm and aurora made for a spectacular
image. (The moon near the horizon illuminated the
Elsewhere in the United States, faint
auroras were sighted or photographed in, e.g., Washington,
Vermont, and Iowa. Browse the aurora
gallery for more...
Aurora Photo Gallery
CME: As Earth's magnetic field reverberates
from one CME strike, a second more potent CME is
on the way. It was propelled in our direction by
sunspot AR1748, which unleashed an M3-class solar
flare on May 17th (0858 UT). Although this is not
the strongest flare we've seen from AR1748, it could
be the most geoeffective; the sunspot was almost-squarely
facing Earth when the blast occurred. NOAA forecasters
estimate a 75% chance of polar geomagnetic storms
when the cloud arrives. Aurora
The Solar and Heliospheric Observatory
took this picture of the CME leaving the sun at
1500 km/s (3.4 million mph) on May 17th:
video, the CME appears to hit Mercury, but it
does not. It is merely passing in front of the innermost
planet. The planet in the line of fire is actually
Space Weather Photo Gallery
IN THE TAIL OF COMET LEMMON: Comet
Lemmon (C/2012 F6), which is receding from the sun
not far beyond the orbit of Earth, has just experienced
a "disconnection event." A cloud of dusty
plasma is propagating down the comet's tail, shown
here in a photo taken by Paul Mortfield on May 15th:
"I was pretty surprised to see
this disconnection event when I processed the images,"
says Mortfield. "The comet is a challenge to
photograph because it is so low in the sky at the
start of morning twilight."
Disconnection events can be caused
by CME impacts. A famous example is that of Comet
Encke in 2007. Comet Lemmon, however, is not
on the same side of the sun as active sunspot AR1748.
It's hard to see how the recent X-flares can be
responsible. Nevertheless, solar activity is high,
so now is a good time to monitor comet tails. They
are very sensitive to stormy space weather.
Comet Lemmon is a pre-dawn object
for observers in the northern hemisphere. It is
currently gliding alongside the Great Square of
Pegasus in the eastern sky before sunrise. The 7th-magnitude
comet is too faint to see with the naked eye, but
it is visible in medium-to-large backyard telescopes.
Observers with computerized GOTO 'scopes should
point their optics here.
More about Comet Lemmon:
Comet Photo Gallery
Aurora Photo Gallery
Noctilucent Cloud Photo Gallery
[previous years: 2003,