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OLD SUNSPOT RETURNS WITH A ***: Active sunspot AR1944, which produced many strong flares
earlier this month, has returned from a two-week trip around the farside of the sun. It announced
itself on Jan. 27th with an M4-class solar flare, shown here in an extreme UV image from
the Solar Dynamics Observatory:
According to tradition, sunspots that circle around the farside of the sun and re-appear
are re-numbered. The new name of AR1944 is AR1967. That's how we shall refer to it from
now on.
Although AR1967 decayed during its absence, it is still potent. NOAA forecasters estimate
a 5% chance of X-flares and a 50% chance of M-flares on Jan. 28th. Explosions probably
won't be Earth-directed, however, because the active region is still near the sun's
southeastern limb. Solar flare alerts: text, voice
RECTANGULAR SUN: No, it's not an alien planet. It's just Rio. On Jan. 23rd, Helio C. Vital
looked out over the ocean from Rio de Janeiro, Brazil, and saw something out of this world--a
rectangular sun:
As alien as it appeared, this was a phenomenon of Earth. "An inversion air layer next to
the sea surface caused the top of the setting sun to acquire unusual shapes. In a matter
of tens of seconds, it went from a saucer to a cup, then to a rectangle," says Vital.
Atmospheric optics expert Les Cowley explains further: "A mirage morphed the sun into a
rectangular block brighter at its top edge. It is even more complex than it seems. Sun
rays are deflected (refracted) through the different temperature layers of a temperature
inversion, cold air trapped beneath warmer air, to form not one sun image but three or
even more. The topmost bright strip is the sun grazing the top of the inversion layer.
Beneath it are two or more sun images, half of them rising and the others descending.
They overlap to form the rectangle. Other shots show the separate sun images."
"Look for these mock-mirages and their green flashes when the horizon shows a dark band
of a temperature inversion," he advises. "But take care and never ever use binoculars or
a telescope. Magnified sunlight can cause serious eye damage."