WHO’S AFRAID OF AN OLD SUNSPOT? Sunspot AR1429, the source of many strong flares and geomagnetic storms earlier this month, has returned, but it’s no longer the behemoth it once was. After a two week transit around the backside of the sun, AR1429 has substantially decayed. All that’s left is a few small dark cores scattered among some bright magnetic froth:
Even the corpse of AR1429 might still be potent, however. Just yesterday it produced a flurry of five C-class flares and sent waves of ionization rippling through the high atmosphere over Europe. Furthermore, NOAA forecasters estimate a 35% chance of M-class flares during the next 24 hours.
Some activity from this diminished active region is certainly possible, but it is unlikely to be anything like the strong storms of early March. Stay tuned for updates
EMERGING SUNSPOT, STRONG FLARE: A big new sunspot is emerging over the sun’s northeastern limb. It announced itself on March 2nd at 1746 UT with anM3-class solar flare. NASA’s Solar Dynamics Observatory recorded the extreme ultraviolet flash:
Although the blast site was partially eclipsed by the solar limb, the flare nevertheless created waves of ionization in Earth’s upper atmosphere. Dave Gradwell of Birr Ireland detected the effect of these waves on the propagation of low-frequency radio signals across Europe. The explosion also hurled a faint CME over the northeastern limb: SOHO movie. The expanding cloud is not Earth-directed.
NOAA forecasters estimate a 55% chance of additional M-class flares and a 5% chance of an X-flare during the next 24 hours. Solar activity is picking up
ADVANCING SUNSPOTS: A phalanx of sunspots is turning toward Earth. Their advance is documented in this two-day movie from the Solar Dynamics Observatory:
The large one in the middle, AR1401, has a “beta-gamma” magnetic field that harbors energy for M-class solar flares. At the moment it is unleashing one such flare every day, such as this flash recorded during the late hours of Jan. 19th. Eruptions from AR1401 will become increasingly geoeffective in the days ahead as the sun’s rotation aligns the active region with our planet.
ACTIVE SUNSPOTS: Crackling with C-class solar flares, a pair of active sunspots is emerging over the sun’s northeastern limb. NASA’s Solar Dynamics Observatory photographed the pair during the early hours of Jan. 15th:
These sunspots have the potential for strong eruptions. Sunspot 1401 produced an M1-flare on Jan. 14th. Two days earlier, while it was still on the farside of the sun, sunspot 1402 produced a partially-eclipsed flare of uncertain magnitude that created waves of ionization in the atmosphere over Europe.
NOAA forecasters estimate a 30% chance of more M-flares during the next 24 hours
Spotless Days Current Stretch: 0 days
2011 total: 2 days (<1%)
2010 total: 51 days (14%)
2009 total: 260 days (71%)
Since 2004: 821 days
Typical Solar Min: 486 days
Updated 25 Dec 2011
SOLAR BLAST:A magnetic prominence dancing along the sun’s southeastern limb became unstable on Nov. 15th and slowly erupted. NASA’s Solar Dynamics Observatory recorded the event, which unfolded over a period of thirteen hours:
The eruption hurled a cloud of plasma (CME) toward Venus. According to a forecast track created by analysts at the Goddard Space Weather Lab, the cloud should reach the second planet on Nov. 17th. Venus has no global magnetic field to protect it from CMEs. The impact will likely strip a small amount of atmosphere from the planet’s cloudtops.
SOLAR ACTIVITY: Sunspot AR1339 is crackling with M-class solar flares, unleashing at least five of them in the past 24 hours. The blasts have been coming with such thick frequency that photographer Randy Shivak of Elyria, Ohio, was able to catch one in action on Nov. 5th:
“Looking like iron filings around a bar magnet, sunspot group 1339 showed itself in the throes of a solar flare,” says Shivak.
Even bigger eruptions are possible before the weekend is over. AR1339 has a delta-class magnetic field that harbors energy for X-class flares. The sunspot is turning toward Earth, so the odds of a geoeffective flare are increasing.
QUIET SUN: How quiet can a star with eight sunspot groups be? Pretty quiet, it turns out. The sun has that many sunspots and more facing Earth, yet none of them is producing flares. Regard this plot of the sun’s X-ray output for the past two days; it has almost flat-lined:
Perhaps this is the calm before the storm. Sunspot AR1319 has a ‘beta-gamma’ magnetic field that harbors energy for strong M-class flares. NOAA forecasters estimate a 30% chance of such an eruption in the next 24 hours
SATELLITE RE-ENTRY: The ROSAT X-ray observatory, launched in 1990 by NASA and managed for years by the German Aerospace Center (DLR), will return to Earth within the next two weeks. Current best estimates place the re-entry between Oct. 22nd and 24th over an unknown part of Earth. Although ROSAT is smaller and less massive than UARS, which grabbed headlines when it re-entered on Sept. 24th, more of ROSAT could reach the planet’s surface. This is because the observatory is made of heat-tolerant materials. According to a DLR study, as many as 30 individual pieces could survive the fires of re-entry. The largest single fragment would likely be the telescope’s mirror, which is very heat resistant and may weigh as much as 1.7 tons.
ROSAT is coming, but it’s not here yet. On Oct. 13th, Marco Langbroek photographed the observatory still in orbit over Leiden, the Netherlands:
Photo details: 5 second exposure, Canon EOS 450D, ISO 400
“I observed ROSAT this evening in deep twilight,” says Langbroek. “It was bright, magnitude +1, and an easy naked-eye object zipping across the sky where the first stars just had become visible.”
Update: Scott Tilley of Roberts Creek, British Columbia, made a video of ROSATon Oct. 15th: “It did get pretty bright, at least 1st magnitude, as it passed overhead after sunset.”
ROSAT will become even brighter in the nights ahead as it descends toward Earth. Local flyby times may be found on the web or on your smartphone.
The role of space weather: Solar activity has strongly affected ROSAT’s decay. Only a few months ago, experts expected the satellite to re-enter in December. However, they did not anticipate the recent increase in sunspot count. Extreme ultraviolet radiation from sunspots has heated and “puffed up” Earth’s atmosphere, accelerating the rate of orbital decay. The massive observatory now has a date with its home planet in October.
