MONSTER SUNSPOT: So you thought Halloween was over? Think again. There is a monster spot on the sun. AR2443 has more than quadrupled in size since it first appeared on Oct. 29th, and it now stretches more than 175,000 km from end to end. Philippe Tosi took this picture of the active region on Nov. 1st from his backyard observatory in Nîmes, France:
The sunspot has more than a dozen dark cores, many of which are as large as terrestrial continents–and a couple as large as Earth itself. These dimensions make it an easy target for backyard solar telecopes.
Of greater interest is the sunspot’s potential for explosive activity. The spotty complex has a ‘beta-gamma’ magnetic field that harbors energy for strong M-class solar flares. Any such explosions will be geoeffective as the sunspot turns squarely toward Earth in the days ahead.
THE SUNSPOT THAT WON’T EXPLODE: Measuring more than 150,000 km wide, sunspot AR2396 is one of the biggest sunspots of the current solar cycle. For the past week it has crossed the solar disk apparently poised to explode. Yet it has not. “It is a sleeping giant,” says Sergio Castillo, who photographed the behemoth from his backyard observatory in Corona, CA:
“AR2396 is huge, but dormant,” says Castillo. “There are very few flares erupting out of it.”
Castillo took the picture using a “Calcium K” filter tuned to the light of ionized calcium atoms in the sun’s lower atmosphere. Calcium K filters highlight the bright magnetic froth that sometimes forms around a sunspot’s dark core. AR2396 is very frothy, indeed.
Magnetic froth, however, does not herald an explosion. It merely means that the sunspot is photogenic.
FULL HALO CME, STORM WARNING: A coronal mass ejection (CME) is heading directly for Earth. It left the sun during the early hours of June 21st, and is expected to sweep up one or two lesser CMEs already en route, before it reaches Earth sometime on June 22nd. Click to view a movie of the “full-halo” CME, then scroll down for more discussion:
NOAA forecasters estimate a 90% chance of polar geomagnetic storms when the CME arrives. This doesn’t mean that a major space weather event is in the offing. The storm could be mild. It all depends on how the magnetic field of the CME connects to the magnetic field of Earth at the time of impact. According to NOAA, there’s only a 10% chance of nothing happening, so stay tuned.
NCREASING CHANCE OF FLARES: NOAA forecasters have boosted the odds of an M-class flare today to 25%. The reasons are circled in this June 12th image from NASA’s Solar Dynamics Observatory:
Sunspots AR2367 (left) and AR2360 (right) are growing with unstable magnetic fields that harbor energy for M-class solar flares. At the moment, both active regions are crackling with low-level C-class flares. It may be just a matter of time before a more significant eruption occurs.
BIG SUNSPOT, CHANCE OF FLARES: Yesterday, sunspot AR2339 unleashed an intense X2-class solar flare. It might not be finished. The active region has doubled in size since yesterday, and it has a ‘beta-gamma’ magnetic field that harbors energy for more eruptions. Amateur astronomer Philippe Tosi sends this picture of the behemoth sunspot from his backyard in Nîmes, France:
As the blue-circular insert shows, several of the sunspot’s dark cores are larger than Earth itself. From end to end, the sunspot group sprawls more than 100,000 km. These dimensions make it an easy target for backyard solar telescopes. If you have one, take a look. You might catch some action. NOAA forecasters estimate a 55% chance of M-class flares and a 10% chance of X-flares on May 7th.
HYDER FLARE MISSES EARTH: Earth-orbiting satellites detected a solar flare on Nov. 1st. Usually solar flares come from sunspots, but there were no sunspots anywhere near this blast. A movie from the Solar Dynamics Observatory shows what happened:
The C3-category flare was caused by a filament of magnetism, which rose up and erupted between 0400 and 0600 UT. Some of the material in the filament fell back to the sun, causing a flash of X-rays where it hit the stellar surface. That was the flare. The rest of the filament flew out into space, forming the core of a massive CME. A movie from the Solar and Heliospheric Observatory shows the CME billowing away from the sun. NOAA analysts say it will not hit Earth.
Flares like this, which happen without sunspots, are called Hyder Flares. They help keep solar activity high even when sunspot counts are low.
SUPER-SUNSPOT PREPARES TO DEPART: The biggest sunspot in nearly 25 years is about to leave the solar disk. This picture from Sergio Castillo of Corona CA shows AR2192 approaching the western limb on Oct. 27th:
“For its final trick, AR2192 is going to treat us by mimicking a Giant Skull,” says Castillo, one of many readers who has noted the resemblance between the sunspot and a skeletal face. “Say Happy Halloween as it gets ready to turn away from us. “
As AR2192 approaches the sun’s horizon, it is no longer facing Earth. However, the odds of an Earth-directed radiation storm are higher than ever. The reason is, the western limb of the sun is well-connected to Earth. Solar magnetic fields springing out of that region spiral back to our planet. If a sunspot passing through the area explodes, those spiralling magnetic fields can funnel energetic particles in our direction.
In only a few days, the behemoth sunspot will begin a 2-week transit of the far side of the sun, carried around by the sun’s 27-day rotation. However, that doesn’t mean we’ve seen the last of this magnificent active region. Big sunspots typically persist for two or three solar rotations before they decay. After it leaves, AR2192 will return in November.
A BEHEMOTH SUNSPOT EMERGES: A large and active sunspot is rotating over the sun’s southeastern limb on Oct. 17th. J. P. Brahic sends this picture of the behemoth from Uzès, France:
“I inserted a picture of Earth for scale,” says Brahic. The sunspot’s primary dark core could swallow our entire planet with room to spare.
This sunspot could cause a sharp increase in solar activity over the weekend. Earlier this week, while it was still hidden behind the southeastern limb, the active region unleashed several M-class solar flares and hurled a massive CME into space. Considering the fact that the blast site was partially eclipsed by the edge of the sun, those flares were probably much stronger than their nominal classification. Now that the sunspot has revealed itself, X-flares may be in the offing.
FAST-GROWNG SUNSPOT: New sunspot AR2175 didn’t exist one day ago. Now it stretches more than 100,000 km across the face of the sun with a primary dark core larger than Earth. The fast-growing region has a ‘beta-gamma’ magnetic field that harbors energy for M-class solar flares.
STORM WARNING (UPDATED): Among space weather forecasters, confidence is building that Earth’s magnetic field will receive a double-blow from a pair of CMEs on Sept. 12th. The two storm clouds were propelled in our direction by explosions in the magnetic canopy of sunspot AR2158 on Sept. 9th and 10th, respectively. Strong geomagnetic storms are possible on Sept. 12th and 13th as a result of the consecutive impacts. Sky watchers, even those at mid-latitudes, should be alert for auroras in the nights ahead. Aurora alerts: text, voice
EARTH-DIRECTED X-FLARE AND CME: Sunspot AR2158 erupted on Sept. 10th at 17:46 UT, producing an X1.6-class solar flare. A flash of ultraviolet radiation from the explosion (movie) ionized the upper layers of Earth’s atmosphere, disturbing HF radio communications for more than an hour. More importantly, the explosion hurled a CME directly toward Earth. The Solar and Heliospheric Observatory photographed the expanding cloud:
Updated: Radio emissions from shock waves at the leading edge of the CME indicate that the cloud tore through the sun’s atmosphere at speeds as high as 3,750 km/s. By the time it left the sun’s atmosphere, however, the cloud had decellerated to 1,400 km/s. This makes it a fairly typical CME instead of a “super CME” as the higher speed might suggest.
Even with a downgrade in speed, this CME has the potential to trigger significant geomagnetic activity when it reaches Earth’s magnetic field during the mid-to-late hours of Sept. 12th. NOAA forecasters estimate an almost-80% chance of polar geomagnetic storms on Sept. 12-13.