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RADIATION
STORM IN PROGRESS: Solar protons
accelerated by this morning's M9-class solar flare
are streaming past Earth. On the NOAA scale of radiation
storms, this one ranks S3,
which means it could, e.g., cause isolated reboots
of computers onboard Earth-orbiting satellites and
interfere with polar radio communications. An example
of satellite effects: The "snow" in this
SOHO coronagraph movie is caused by protons
hitting the observatory's onboard camera.
ALMOST-X
FLARE AND CME (UPDATED):
This morning, Jan. 23rd around 0359 UT, big sunspot
1402 erupted, producing a long-duration M9-class
solar flare. The explosion's M9-ranking
puts it on the threshold of being an X-flare, the
most powerful kind. NASA's Solar Dynamics Observatory
captured the flare's extreme ultraviolet flash:
The Solar and Heliospheric Observatory
(SOHO) and NASA's STEREO-B spacecraft detected a
CME rapidly emerging from the blast site: movie.
Analysts at the Goddard Space Weather Lab say the
leading edge of the CME will reach Earth
on Jan. 24 at 14:18UT (+/- 7 hours). Their
animated
forecast track shows that Mars is in the line
of fire, too; the CME will hit the Red Planet during
the late hours of Jan. 25.
This is a relatively substantial and
fast-moving (2200 km/s) CME. Spacecraft in geosynchronous,
polar and other orbits passing through Earth's ring
current and auroral regions could be affected by
the cloud's arrival. In addition, strong geomagnetic
storms are possible, so high-latitude sky watchers
should be alert for auroras. Magnetic
storm alerts: text,
voice.
JAN.
22ND 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 CME strongly compressed Earth's magnetic
field and briefly exposed satellites in geosynchronous
orbit to solar wind plasma. For the next 24 hours,
Earth's magnetic field reverberated from the impact,
stirring bright
auroras around the Arctic Circle. Bjørn Jørgensen
observed this display from Tromsø, Norway:
"This was amazing," he says.
"It was a wonderful experience to see these
stunning auroras."
NOAA forecasters estimate a 10% -
25% chance of continued geomagnetic storms tonight
as effects from the CME impact subside. The odds
will increase again on Jan. 24-25 as a new CME (from
today's M9-clare) approaches Earth. High-latitude
sky watchers should remain alert for auroras. Aurora
alerts: text,
voice.
UPDATED:
January
2012 Aurora Gallery
[previous Januaries: 2010,
2009,
2008,
2007, 2005,
2004]
The Jan. 22nd CME 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.
Comet
Lovejoy Gallery
[previous comets: McNaught,
Holmes,
Lulin,
Tuttle,
Ikeya-Zhang]
