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.
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.
OLAR FLARE AND RADIO BLACKOUT: Sunspot AR2257 erupted on Jan. 13th, producing an M5-class solar flare at 04:24 UT. A pulse of extreme UV radiation from the flare ionized Earth’s upper atmosphere over Australia and the Indian Ocean. Mariners and ham radio operators may have noticed a brief communications blackout at frequencies below about 10 MHz. This map from NOAA shows the affected region:
We do not yet know if the flare also produced a coronal mass ejection (CME). If so, the plasma cloud will probably miss Earth because of the sunspot’s off-center location on the solar disk.
More flares could be in the offing. AR2257 has an unstable ‘beta-gamma-delta’ magnetic field that seems poised to explode again. NOAA forecasters estimate a 40% chance of M-class flares and a 10% chance of X-flares on Jan. 13th.
HOLE IN THE SUN’S ATMOSPHERE: A vast hole has opened in the atmosphere over the sun’s south pole, and it is spewing solar wind into space. The gaseous gap, a.k.a. a ‘coronal hole,’ is colored dark-purple in this extreme ultraviolet image from NASA’s Solar Dynamics Observatory:
Curved lines trace the sun’s magnetic field in this EUV image from SDO
Coronal holes are places where the sun’s magnetic field opens up and allows solar wind to escape. A stream of solar wind flowing from this particular hole is expected to reach Earth’s orbit on Jan. 4-5. The bulk of the stream will flow south of our planet. However, not all of it will miss. NOAA forecasters estimate a 40% chance of polar geomagnetic storms when the solar wind arrives in the next 48 hours.
CME TARGETS EARTH, AFTER ALL: On Nov. 7th, when an X-flare from AR2205 hurled a CME into space, at first it appeared that the cloud would miss Earth. Follow-up computer modeling by NOAA analysts suggests that the CME might deliver a glancing blow to our planet’s magnetic field after all. A complete forecast follows this movie of the eruption recorded by the Solar and Heliospheric Observatory:
The CME left the sun traveling approximately 600 km/s (1.3 million mph) albeit not directly along the sun-Earth line. If the computer models are correct, the outskirts of the cloud should reach Earth mid-day on Nov. 10th (Universal Time). First contact could spark a G2-class geomagnetic storm on Nov. 10th subsiding to G1-class on Nov. 11th. NOAA forecasters are citing storm probabilities as high as 75%.
These storms in the forecast are mild, not extreme, so there is no danger of power outages or communications blackouts. However, the CME impact could spark some beautiful auroras around the Arctic Circle. The lights might even spill across the Canadian border into northern-tier US states such as Maine, Michigan, Minnesota and the Dakotas.
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.