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HIGH-LATITUDE
AURORAS: The Arctic Circle is alight
with auroras following this morning's CME impact.
Incoming reports from
Russia,
Denmark,
Scotland,
England,
and Norway
confirm a bright apparition underway now. Aurora
alerts: text,
voice.
CME
IMPACT: Arriving a little later
than expected, a coronal mass ejection (CME) hit
Earth's magnetic field at 0617 UT on Jan. 22nd.
According to analysts at the Goddard Space Weather
Lab, the impact strongly compressed Earth's magnetic
field and briefly exposed satellites in geosynchronous
orbit to solar wind plasma. Shifting lines of magnetic
force induced strong ground
currents in Norway and sparked bright auroras
over the upper reaches of North America. This colorful
corona appeared over Chatanika, Alaska:
"We enjoyed some amazing
displays as the late arriving CME made its presence
felt," says photographer Ronn Murray.
The impact also disturbed Earth's
ionosphere. In Atlanta, Georgia, radio engineer
Pieter Ibelings monitored a 4.5 MHz CODAR
(coastal radar) signal as it bounced off layers
of ionization along the US east coast. "The
moment of impact can be clearly seen on the CODAR
radar plot," he points out:
"The CODAR transmitters are located
all around the coast and are used for mapping the
ocean currents to a distance of about 200 miles,"
Ibelings explains. "These signals also propagate
through the ionosphere so they can be picked up
all around the world. The signals are almost perfect
for ionospheric sounding since they are linear chirps.
I capture the chirp with a receiver locked to GPS
both in frequency and time. I then de-chirp the
waveform so I can extract the time of arrival information
at my location."
The CODAR echoes show ionization layers
shifting vertical position by some hundreds of kilometers,
changes that surely affected the propagation of
HF radio signals in the aftermath of the impact.
More information about Ibelings' observations may
be found here.
more aurora images:
from
Lance Parrish of Skiland, Alaska; from
Coby Brock of North Pole, Alaska; from
Phil Hart of Lake Laberge, Yukon, Canada; from
Jason Ahrns of Chatanika, Alaska; from
John Dean of Nome, Alaska; from
Sam Tsai of Grande Prairie, Alberta, Canada;
from
Chad Blakley of Aurora Sky Station, Abisko National
Park, Sweden; from
Andrei Penescu of Kangerlussuaq, Greenland;
from
Marketa Stanczykova of Chatanika, Alaska; from
Kimberly S Mietzah Damkoehler of Houston, Alaska;
January
2012 Aurora Gallery
[previous Januaries: 2010,
2009,
2008,
2007, 2005,
2004]
INCREASING
SOLAR ACTIVITY CLEANS UP SAT-DEBRIS:
Earth's atmosphere has been puffing up in response
to increasing levels of UV radiation from sunspots.
This is good news for satellite operators, because
a puffed up atmosphere helps clean up low-Earth
orbit. "The number of cataloged debris in Earth
orbit actually decreased during 2011," reports
Nick Johnson in NASA's Orbital
Debris Quarterly newsletter. "[The figure
below] illustrates how the rate of debris reentries
from the Fengyun-1C anti-satellite test of January
2007 increased during the past year."
"Even though only 6% of the total
3218 cataloged debris from the ill-advised engagement
had reentered by the end of 2011, half of
these debris fell out of orbit in the past 12 months,"
he points out. "Likewise, many debris from
the 2009 accidental collision of Cosmos 2251 and
Iridium 33 are accelerating their departure from
Earth orbit. In the absence of a new major satellite
breakup, the overall orbital debris population should
continue to decrease during 2012 and 2013."
Comet
Lovejoy Gallery
[previous comets: McNaught,
Holmes,
Lulin,
Tuttle,
Ikeya-Zhang]
