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.
SUNDIVING COMET DESTROYED: The solar system now has one less comet. Earlier today, a sundiving comet discovered on Sept. 15th by Worachate Boonplod, a science writer from Thailand, passed too close to the sun and apparently evaporated. A coronagraph onboard the Solar and Heliospheric Observatory (SOHO) recorded the death plunge:
One comet went in, no comets came out. Fierce heat from the sun likely evaporated the comet’s fragile ices, transforming it into a disintegrated cloud of gas and dust.
Sundiving comets are more common than you might think. SOHO has found more than 3000 of them. Most are members of the Kreutz family. Kreutz sungrazers are fragments from the breakup of a single giant comet many centuries ago. They get their name from 19th century German astronomer Heinrich Kreutz, who studied them in detail. Kreutz fragments pass by the sun and disintegrate almost every day. Most, measuring less than a few meters across, are too small to see, but occasionally a bigger fragment like this one attracts attention.
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.
FARSIDE SOLAR ACTIVITY: Solar activity has been very low for more than two weeks. A change could be in the offing. During the early hours of August 3rd, a new active region on the farside of the sun announced itself with a bright CME. The Solar and Heliospheric Observatory (SOHO) recorded the eruption:
The CME is not heading for Earth. It is billowing away from the sun’s farside, well off the sun-Earth line.
What’s next? Because the blast site is hidden behind the sun’s limb, we cannot yet inspect it and assess its potential for future eruptions. However, it should rotate into view in the days ahead, possibly bringing an end to two weeks of quiet.
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.
OLSTICE AURORA WATCH: On June 18th, sunspot AR2371 unleashed the strongest solar flare in nearly 2 months. The M3-class explosion caused a brief shortwave radio blackout over North America, and it hurled a CME into space. SOHO (the Solar and Heliospheric Observatory) recorded a movie of the expanding cloud:
The CME is not heading directly for Earth. Nevertheless, it is probably geoeffective. According to NOAA computer models, the CME should deliver a glancing blow to our planet’s magnetic field during the late hours of June 21st. High-latitude sky watchers should be alert for solstice auroras.
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.
X-FLARE: The sun is no longer quiet. Emerging sunspot AR2339 unleashed an intense X2-class solar flare on May 5th at 22:11 UT. NASA’s Solar Dynamics Observatory captured the extreme ultraviolet flash:
A pulse of UV radiation and X-rays from the flare caused a strong radio blackout over the Pacific side of Earth. This map shows the extent of the blackout, which affected frequencies below 20 MHz. Mariners, aviators, and ham radio operators are the type of people who might have noticed the disturbance.
The explosion also hurled a CME into space: movie. Traveling faster than 1100 km/s (2.5 million mph), the expanding cloud does not appear to be heading for Earth.
In addition to causing a radio blackout, the flare also caused a radio burst. Immediately after the flare, a roar of static bellowed from the loudspeakers of shortwave receivers on Pacific isles and western parts of North America. Amateur radio astronomer Thomas Ashcraft of New Mexico recorded the outburst:
“The sound file is in stereo with one channel at 22 MHz and the other at 23 MHz,” says Ashcraft. “It is very intricate if listened to with headphones.”
What caused this burst of “solar static”? The same magnetic explosion that caused the flare also produced beams of electrons. As the electrons sliced through the sun’s atmosphere, they generated a ripple of radio-loud plasma waves. Astronomers classify solar radio bursts into five types; this one was a mixture of Type III and Type V.
CME, POSSIBLY EARTH-DIRECTED: A magnetic filament snaking around the sun’s southern hemisphere erupted on May 3rd. The blast did not create a pulse of electromagnetic radiation (i.e., a solar flare), but it did hurl a CME into space. The Solar and Heliospheric Observatory recorded the expanding cloud:
Although the CME is not moving directly along the sun-Earth line, it might still be geoeffective. A glancing blow is possible on May 5th or 6th. NOAA analysts are evaluating this possibility as they receive additional coronagraph data. Stay tuned for updates in the hours ahead.