AURORA ALERTS: Did you miss the Northern Lights? Next time
get a wake-up call from Space
Weather PHONE |
|
|
SPACECRAFT
TO PLUNGE INTO THE SUN: NASA's daring plan
to visit the sun took a giant leap forward this week with
the selection of five key science investigations for the Solar
Probe+ spacecraft. Get the full
story from Science@NASA.
LIMB
EXPLOSION: On Sept. 4th around 1600 UT, a
magnetic filament erupted and hurled a massive coronal mass
ejection (CME) off the sun's northwestern limb. Click on the
image to view a close-up movie of the blast from NASA's Solar
Dynamics Observatory:
Another
movie from the Solar and Heliospheric Observatory (SOHO)
shows the CME billowing into space. The cloud is not heading
toward Earth, and no geomagnetic storms are expected from
this blast.
However, space weather could be in the offing
for a different reason. A solar wind stream is heading for
Earth and it could spark auroras when it arrives on Sept.
5th or 6th. NOAA forecasters estimate a 50% chance of geomagnetic
activity at high latitudes. People in Alaska, Canada, Scandinavia
and Antarctica should be alert for auroras in the nights ahead.
August
2010 Northern Lights Gallery
[previous Augusts: 2009,
2008, 2007,
2006, 2005,
2004, 2003]
VIRTUAL
REALITY PARHELIC CIRCLE: A parhelic
circle is an unforgettable sight. Thin and pale, it circles
the zenith in a majestic arc, always keeping the same distance
above the horizon. "I've been looking for a parhelic
circle for more than 13 years," says photographer Laurent
Laveder of Pluguffan, France. "Yesterday I finally
saw one." He rushed for his camera and quickly snapped
enough pictures to assemble a complete 360o zenith-to-horizon
composite view of the phenomenon. Click on the image below
to experience the VR
parhelic circle:
Parhelic circles are caused by sunlight reflecting from the
vertical faces of ice crystals--millions of them floating
in thin cirrus clouds spread almost evenly across the wide
blue sky. As Les Cowley notes in his authoritative
web page on the subject, "the parhelic circle appears
simple yet more ray paths contribute to it than in any other
halo. Some are very intricate."
A striking aspect of the parhelic circle is its dual personality.
At the same time it appears both circular and straight. "These
two pictures (1,
2) illustrate
the effect," says Laveder. More images may be found here.
|
