https://spaceweather.com/
Sunspot AR3615, last seen in March crackling with X-flares, is now transiting the farside of the sun. The sunspot is so big, it is affecting the way the sun vibrates, allowing researchers to detect its seismic echo. Also, NASA's rover Perseverance can see the sunspot all the way from Mars. This large active region will return to the Earthside of the sun about a week from now.
https://spaceweather.com/
0 Comments
Yesterday (9 February) at 13.14 UT, the sun produced one of the most powerful solar flares in years, an X3.4-class explosion from just behind the sun's southwestern limb. NASA's Solar Dynamics Observatory (SDO) recorded the extreme ultraviolet flash: The source of the flare appears to be departing sunspot AR3575. Because the blast site was eclipsed by the edge of the sun, the flare was probably even stronger than its X3.4 classification suggests. This was a big explosion. Hours after the flare's peak, Earth was still feeling the effects of the blast. Solar protons energized by the flare are following curved magnetic field lines from the sunspot back to our planet. The resulting hailstorm, called a "radiation storm," is still intensifying at the time of this writing (9 February) and has just reached category S2: This plot shows what NOAA's GOES-18 satellite is seeing right now. The colored lines count the number of energetic protons streaming past the satellite en route to Earth. Green and blue are of special interest because they trace "hard protons" capable of upsetting spacecraft electronics, e.g., causing reboots of onboard computers and temporarily fogging cameras. The explosion also hurled a bright CME into space. It will not hit Earth. Instead, a NASA model of the CME shows it is heading for Mercury, Venus and Mars. It will hit all three planets this weekend. 10 February 2024: For the second day in a row, energetic protons from the sun are raining down on Earth. This is called a "solar radiation storm," and it is currently a category S2 event. A data-plot from NOAA's GOES-18 satellite shows how protons surged around our planet just after yesterday's X-class solar flare: The colored lines count the number of energetic protons streaming past GOES-18 en route to Earth. Green and blue are of special interest because they trace "hard protons" capable of upsetting spacecraft electronics, e.g., causing reboots of onboard computers. These particles can even reach all the way down to aviation altitudes, boosting dose rates for passengers and crews flying commercial planes over Earth's polar regions. We can actually *see* some of these protons. Take a look at this SOHO coronagraph movie of the sun hours after the flare: The "snow" in this movie is caused by the radiation storm. Each speckle is a solar proton striking the spacecraft's digital camera. This is a good example of how radiation storms can temporarily interfere with orbital imaging systems.
Another effect of the radiation storm is an ongoing blackout of shortwave radio transmissions around Earth's poles. This is called a "polar cap absorption event". Earth's magnetic field is guiding many of the incoming protons towards the poles, where they ionize the upper atmosphere; this, in turn, wipes out radio signals below 30 MHz. Many shortwave radios inside the Arctic Circle simply won't work until the radiation storm is over. https://spaceweather.com Recent measurements by NASA's Solar Dynamic Observatory reveal a rapid weakening of magnetic fields in the polar regions of the sun. North and south magnetic poles are on the verge of disappearing. This will lead to a complete reversal of the sun's global magnetic field perhaps before the end of the year. An artist's concept of the sun's dipolar magnetic field. Credit: NSF/AURA/NSO. If this was happening on Earth there would be widespread alarm. Past reversals of our planet's magnetic field have been linked to calamities ranging from sudden climate change to the extinction of the Neanderthals. On the sun, it's not so bad. "In fact, it's routine", says Todd Hoeksema, a solar physicist at Stanford University. "This happens every 11 years (more or less) when we're on the verge of Solar Maximum." Vanishing poles and magnetic reversals have been observed around Solar Max in every single solar cycle since astronomers learned to measure magnetic fields on the sun. Hoeksema is the director of Stanford's Wilcox Solar Observatory (WSO), that is observing its fifth reversal since 1980. The last five polar field reversals observed at the Wilcox Solar Observatory (inset) "One thing we have learned from these decades of data is that no two polar field reversals are alike," he says. Sometimes the transition is swift, taking only a few months for the poles to vanish and reappear on opposite ends of the sun. Sometimes it takes years, leaving the sun without magnetic poles for an extended period of time. "Even more strange," says Hoeksema, "sometimes one pole switches before the other, leaving both poles with the same polarity for a while." Indeed, such a scenario could be playing out now. The sun's south magnetic pole has almost completely vanished, but the north magnetic pole is still hanging on, albeit barely. How does all this affect us on Earth? One way we feel solar field reversals is via the heliospheric current sheet: An artist's concept of the heliospheric current sheet. The sun is surrounded by a wavy ring of electricity that the solar wind pulls and stretches all the way out to the edge of the Solar System. This structure is a part of the sun's magnetosphere. During field reversals, the current sheet becomes extra wavy and highly tilted. As the sun spins, we dip in and out of the steepening undulations. Passages from one side to another can cause geomagnetic storms and auroras.
Most of all, the vanishing of the poles means we're on the verge of Solar Maximum. Solar Cycle 25 is shaping up to be stronger than forecasters expected, and its peak could be relatively intense. Stay tuned for updates! https://spaceweather.com/ For the second month in a row, sunspot counts in the sun's northern hemisphere are more than double the south. The asymetry is obvious in this summary of September's sunspots compiled by astronomer Senol Sanli using data from NASA's Solar Dynamics Observatory: According to the Royal Observatory of Belgium's Solar Influences Data Analysis Center, in September the monthly sunspot number for the sun's northern hemisphere was 90, the southern hemisphere was only 44; that's a ratio of 2-to-1 in favor of the north. August was about the same. Looking back over an entire year, the north is leading the south by an average of 50%. What's going on? In fact, it's not unusual for the sun's northern and southern hemispheres to be out of synch. As long ago as the 19th century, solar cycle pioneers Spoerer (1889) and Maunder (1890) noted that there were often long periods of time when most sunspots were found preferentially in one hemisphere and not the other. This plot from the Royal Observatory of Belgium shows assymetries throughout the last 6 solar cycles: Until recently, Solar Cycle 25 was pretty evenly matched, north vs. south. Sunspot counts from August and September, however, suggest that the northern hemisphere may be seizing control--at least temporarily. This has happened during the upslope of all four previous solar cycles (21-24).
One possible explanation for this phenomenon may be that the two hemispheres of the sun have their own solar cycles, one out of phase with the other by about a year. Indeed, Solar Max is often double peaked. You can see it in the hemispheric sunspot plot. In the three most recent cycles (22-24), north peaked before south, creating two surges of solar activity separated by a "Gnevyshev gap." Solar Cycle 25 might continue this trend. A complete discussion of sunspot asymmetries is included in David Hathaway's excellent review article "The Solar Cycle." https://spaceweather.com/ If you're a satellite, this story is important. A series of geomagnetic storms in 2023 has pumped terawatts of energy into Earth's upper atmosphere, helping to push its temperature and height to a 20-year high. Air surrounding our planet is now touching satellites in Earth orbit and dragging them down. "Blame the sun," says Martin Mlynczak of NASA Langley. "Increasing solar activity is heating the top of the atmosphere. The extra heat has no effect on weather or climate at Earth's surface, but it's a big deal for satellites in low Earth orbit." Above: A severe geomagnetic storm on March 24, 2023, photographed by Michael Underwood from Yellowstone National Park Mlynczak is an expert on the temperature up there. For 20 years he has been using the SABER instrument on NASA's TIMED satellite to monitor infrared emissions from "the thermosphere," the uppermost layer of the atmosphere."Right now we’re seeing some of the highest readings in the mission's 21.5 year history," he says. The thermosphere is exquisitely sensitive to solar activity, readily absorbing energy from solar flares and geomagnetic storms. These storms have been coming hard and fast with the recent rise of Solar Cycle 25. "There have been five significant geomagnetic storms in calendar year 2023 that resulted in marked increases in the amount of infrared radiation (heat) in Earth's thermosphere," says Mlynczak. "They peaked on Jan. 15th (0.59 TW), Feb. 16th (0.62 TW), Feb. 27th (0.78 TW), Mar. 24th (1.04 TW), and April 24th (1.02 TW)." The parenthetical values are TeraWatts (1,000,000,000,000 Watts) of infrared power observed by SABER during each storm. The sensor obtains these numbers by measuring infrared radiation emitted from nitric oxide and carbon dioxide molecules in the thermosphere. Above: NASA's daily Thermosphere Climate Index tracks thermal energy in Earth's upper atmosphere. So far, Solar Cycle 25 is far ahead of Solar Cycle 24. Credit: Linda Hunt "The two storms exceeding 1 TW are the seventh and eighth strongest storms observed by SABER over the past 21.5 years," he says. "It is interesting to note that each successive storm in 2023 is generally stronger than its predecessors."Actually, it doesn't take a strong storm to cause problems. In Feb. 2022, a minor geomagnetic storm dumped enough heat into the thermosphere that 38 newly launched Starlink satellites fell out of the sky. SpaceX has since started launching their Starlinks to higher initial altitudes to avoid the drag.
If current trends continue, the thermosphere will warm even more in 2023 and 2024. This is a matter of concern because Earth's population of active satellites has tripled since SpaceX started launching Starlinks in 2019. The growing constellation of 4100 Starlinks now provides internet service to more than a million customers. An extreme geomagnetic storm like the Halloween Storms of 2003 could shift the positions of these satellites by many 10s of kilometers, increasing the risk of collisions and causing some of the lowest ones to de-orbit. Stay tuned as the warming continues. https://spaceweather.com BBC: Sat, 27 May 2023 14:01 UTC A halo, with sun dogs and tangent arcs, was spotted over the Headland in Hartlepool by Ash Foster Much of northern England enjoyed a rare optical display on Sunday evening. Thin, high cloud gave a spectacular show of halos, arcs and upside-down rainbows across the North East and Cumbria, not often seen together in the UK. The phenomena are caused by sunlight reflecting and refracting through ice crystals high in the atmosphere. BBC Look North weather presenter Jennifer Bartram said it was "very unusual". "The particular angle at which the sunlight hits these high-up ice crystals form these patterns," she said. "It's a real delight to see." The rings around the Sun are known as halos and have a reddish tinge on the inner edge. Halos gave the perfect frame around the Angel of the North, spotted by Andy Gowland Though halos are not uncommon in the UK, the combination of other optical effects is more unusual. © Daniel McTiernan The unusual solar effects shone over Whitley Bay on Sunday. One of the more unusual features spotted was an upside-down rainbow, known as a cirumzenithal arc. It is also known as a Bravais' arc, and is formed when sunlight enters horizontal ice crystals and refracts through a side prism face, which causes the upside-down effect. A bright circumzenithal arc spotted in Stanwix, Cumbria, by Weather Watcher Ravi Steven Lomas captured the stunning spectacle over Souter Point lighthouse Also visible were a range of other effects, including parhelia - or sun dogs - which appear as bright patches either side of the sun. A rare sighting of halos, arcs and sun dogs were spotted in Whale, just outside Penrith,
by Kim Skelton A parhelic circle is an unforgettable sight. Thin and pale, it circles the zenith in a majestic arc, always keeping the same distance above the horizon. Two days ago, R. J Cobain saw this one over Conlig, Northern Ireland: "I was shaking as I took as many photos as I could," says Corbin. "By combining 11 photos I was able to capture the full circle."
This was part of a great display of ice halos widely seen and reported across Northern Ireland and Northern England on May 28th. A weather system blanketed the region with a rare mixture of gem-like ice crystals in wispy cirrus clouds. Sunlight shining through the crystals produced a stunning variety of forms. A full parhelic circle is among the rarest of ice halos. It requires as many as five internal reflections from millions of individual ice crytals, all catching sunbeams simultaneously. "This was by far the best display of atmospheric optics I have ever seen," Corbin says. more images: from Alan Fitzsimmons of Belfast, Northern Ireland; from Mike Devenport of Gateshead, UK; from Ian Lee of Carlisle, Cumbria, UK. https://spaceweather.com/ Before the launch of the Solar and Heliospheric Observatory (SOHO) in 1995, astronomers had never seen anything like this. Behold, a solar storm passing directly in front of the Pleiades: SOHO recorded this rare conjunction on May 21st. An erupting filament of magnetism near the sun's north pole propelled the CME into space just as the Seven Sisters were passing by. Electra, Taygete, Maia, Celaeno, Alcyone, Sterope, and Merope spent nearly three hours shining through the translucent solar storm.
When SOHO left Earth almost 30 years ago, it carried the first realtime coronagraph into space. Coronagraphs are devices that create an artificial eclipse, blocking the glare of the sun to reveal nearby stars, planets, and comets. No telescope on Earth could see something as faint as the Pleiades only a few degrees from the sun, but SOHO does it all the time. https://spaceweather.com/ Tomorrow, April 20th, a rare hybrid solar eclipse will sweep across Australia and Indonesia. Eclipse chaser Mohamad Sol couldn't wait. One day early, he snapped this picture of the Moon from inside the path of totality: "Just the day before the total solar eclipse, I observed this fabulous moonrise from Exmouth, Australia, where the eclipse will be total on April 20th," says Sol. A hybrid eclipse is a mixture of two types: an annular eclipse and a total eclipse. The difference is the size of the Moon. During the annular phase, the Moon is slightly too small to cover the entire solar disk, resulting in a "ring of fire." During the total phase, the whole sun is covered, revealing the sun's ghostly corona. Tomorrow's eclipse begins as an annular eclipse over the Indian Ocean, transitions into a total eclipse as it moves over western Australia, then becomes an annular eclipse again over the South Pacific. The last time such a hybrid eclipse occurred was Nov. 3, 2013.
Outside the narrow red path (shown above), the eclipse will be partial--neither annular nor total. The sun will still be very bright, but shaped like a crescent as the Moon takes a bite out of the solar disk. Observers in this broad region can look directly at the eclipsed sun using safe solar eclipse glasses. www.spaceweather.com Something rare and strange happened last month. On Feb. 23rd, growing sunspot AR3234 produced an M-class solar flare. It was nearly midnight in Florida when the explosion occurred, so you'd expect no one there to notice. On the contrary, in the community of High Springs, FL, amateur radio astronomer Dave Typinski recorded a strong shortwave radio burst. "You CAN see the sun at midnight in Florida... sometimes," says Typinski. This is what his instruments recorded while the flare was underway: A double wave of static washed over Florida, filling the radio spectrum with noise at all frequencies below 25 MHz. "The Sun was 69° below the horizon when this happened," he marvels. How is this possible? The entire body of our planet was blocking the event from Typinski's antenna. It's called "antipodal focusing". First postulated by Marconi more than 100 years ago, antipodal focusing is a mode of radio propagation in which a signal starts out on one side of the planet, gets trapped between Earth's surface and the ionosphere, and travels to the opposite hemisphere. Waves converging at the antipode can create a surprisingly strong signal. "This is the second or maybe third midnight solar radio burst I've seen in ten years, but it's by far the strongest," says Typinski. "The previous events happened at the height of Solar Cycle 24. They're quite rare." This diagram from a declassified US Gov.report shows the basic geometry of antipodal focusing. Pause: Yes, solar flares can produce radio signals. Typinski's midnight burst was a "Type V", caused by streams of electrons shooting through the sun's atmosphere in the aftermath of the flare. Plasma waves rippling away from the streams emited intense bursts of natural radio static. The burst was first observed in broad daylight at the Learmonth Solar Observatory in Australia, then it curved around Earth to reach Typinski. Above: An example of antipodal focusing of seismic waves caused by the Chicxulub asteroid impact. The geometry is the same as for radio waves. [more]. "This propagation mode was used during the Cold War," notes Typinski. "The U.S. would park a SIGINT ship in the south Pacific to grab signals from the Eastern Bloc. The Soviets probably did the same thing, parking in the southern Indian ocean."
Turns out, this method of spying works for radio astronomers, too. Would you like to record an event like this? NASA's Radio JOVE program makes it easy. Off-the-shelf radio telescope kits allow even novices to monitor radio outbursts from the sun, which are becoming more frequent as Solar Cycle 25 intensifies. www.spaceweather.com Cosmic rays reaching Earth just hit a six-year low. Neutron counters in Oulu, Finland, registered the sudden decrease on Dec. 26th when a coronal mass ejection (CME) hit Earth's magnetic field: The CME swept aside galactic cosmic rays near our planet, abruptly reducing radiation levels. Researchers call this a "Forbush Decrease," after American physicist Scott Forbush, who studied cosmic rays in the early 20th century. The Dec. 26th event continues a trend that began in 2020. Since then, cosmic ray fluxes have been fitfully decreasing as one CME after another hit Earth. The reason is Solar Cycle 25, which began around that time and has been gaining strength. The Forbush Decreases are adding up. Scott Forbush was the first to notice the yin-yang relationship between solar activity and cosmic rays. When one goes up, the other goes down. CMEs play a big role in this relationship. The solar storm clouds contain tangled magnetic fields that do a good job scattering cosmic rays away from our planet. A recent paper in the Astrophysical Journal looked at the last two solar cycles and compared the daily rate of CMEs to the strength of cosmic rays near Earth. This plot shows the results: At the peak of Solar Cycle 24, the sun was producing more than 5 CMEs per day. At the same time, galactic cosmic rays (GCRs) dropped more than 60%.
Neutron counts are now at their lowest level since 2016. If current trends continue, cosmic ray levels will plunge even further in the years ahead, perhaps even lower than Solar Cycle 24. This is good news for astronauts and polar air travelers who will benefit from less radiation. FAQ: Why neutrons? When cosmic rays strike Earth’s atmosphere, they produce a spray of secondary particles that rain down on Earth. Among these particles are neutrons, which can make it all the way down to Earth's surface. Researchers at the Sodankyla Geophysical Observatory in Oulu, Finland, have been counting neutrons every day since 1964, providing an unparalleled record of cosmic rays for almost 60 years. www.spaceweather.com It seemed like sunspot AR3088 would never stop exploding. Over the past four days, the strangely-magnetized active region produced more than a dozen M-class solar flares: Each X-ray peak in the graph above produced a corresponding shortwave radio blackout on Earth. No part of our planet was untouched. More than half of the explosions also produced a coronal mass ejection (CME). Earth dodged them all. Only one and maybe two delivered glancing blows of no consequence. All the rest sailed harmlessly into space. The simple reason why: AR3088 was never facing Earth. Most of the explosions occurred while the sunspot was approaching or even rounding the sun's western limb. This movie from NASA's Solar Dynamics Observatory is a good example. It shows a flare from AR3088 on Aug. 29th partially eclipsed by the edge of the sun. The explosion registered M9 on GOES satellite X-ray sensors, but the uneclipsed flare was probably much stronger--perhaps even an X-flare.
If the sunspot had been facing us, we might now be experiencing strong geomagnetic storms with spectacular low-latitude auroras. Maybe next time... https://spaceweather.com/ Photographers consider themselves lucky when they catch a green flash. The sunset emerald ray is so rare, it was once thought to be a fable. Now imagine the odds of catching a triple green flash. James W. Young did it last night while standing on Oregon's Cannon Beach: "The setting sun produced a green flash which split into three layers," marvels Young. "I photographed them using a 1120mm telephoto lens with a Canon 1Dx Mark II camera."
This is a sign of very strong temperature inversions (warm air above cold) over the Pacific Ocean. Strong inversions produce 'ducts'. Rays from the setting sun get trapped in these ducts, bouncing up and down and traveling long distances in layers sometimes only a few inches thick. A trio of ducts split the green flash into a stack of three. You can actually see the ducts edge-on in Young's picture--a marvel, indeed. https://spaceweather.com/
Sept. 24, 2021: No solar storms? No problem. Earth has learned to make its own auroras. New results from NASA’s THEMIS-ARTEMIS spacecraft show that a type of Northern Lights called “diffuse auroras” comes from our own planet – no solar storms required.
Diffuse auroras look a bit like pea soup. They spread across the sky in a dim green haze, sometimes rippling as if stirred by a spoon. They’re not as flamboyant as auroras caused by solar storms. Nevertheless, they are important because they represent a whopping 75% of the energy input into Earth’s upper atmosphere at night. Researchers have been struggling to understand them for decades.
Above: Diffuse auroras and the Big Dipper,
photographed by Emmanuel V. Masongsong in Fairbanks, AK
“We believe we have found the source of these auroras,” says UCLA space physicist Xu Zhang, lead author of papers reporting the results in the Journal of Geophysical Research: Space Physics and Physics of Plasmas.
It is Earth itself. Earth performs this trick using electron beams. High above our planet’s poles, beams of negatively-charged particles shoot upward into space, accelerated by electric fields in Earth’s magnetosphere. Sounding rockets and satellites discovered the beams decades ago. It turns out, they can power the diffuse auroras. The video below shows how it works. The beams travel in great arcs through the space near Earth. As they go, they excite ripples in the magnetosphere called Electron Cyclotron Harmonic (ECH) waves. Turn up the volume and listen to the waves recorded by THEMIS-ARTEMIS:
Above: A great electrical circuit in space powering diffuse auroras. ECH waves were sonified by NASA’s HARP (Heliophysics Audified: Resonances in Plasmas) software.
ECH waves, in turn, knock other electrons out of their orbits, forcing them to fall back down onto the atmosphere. This rain of secondary electrons powers the diffuse auroras.
“This is exciting,” says UCLA professor Vassilis Angelopoulos, a co-author of the papers and lead of the THEMIS-ARTEMIS mission. “We have found a totally new way that particle energy can be transferred from Earth’s own atmosphere out to the magnetosphere and back again, creating a giant feedback loop in space.” According to Angelopoulos, Earth’s polar electron beams1 sometimes weaken but they never completely go away2, not even during periods of low solar activity. This means Earth can make auroras without solar storms. The sun is currently experiencing periods of quiet as young Solar Cycle 25 sputters to life. Pea soup, anyone? [Note: Solar Cycle 25 is accelerating. MS} End Notes: (1) Why do these electron beams exist? Earth’s magnetosphere is buzzing with energetic particles. Many of them are captured from the solar wind. When these particles strike the top of Earth’s atmosphere (the ionosphere), they dislodge electrons. Electric fields, which form naturally in Earth’s spinning magnetosphere, grab the liberated electrons and accelerate them skyward in collimated beams. (2) Why don’t the beams ever go away? Short answer: because the solar wind never stops blowing. Even when the sun is quiet, Earth’s magnetosphere is jostled and energized by the ever-present solar wind. As a result, electrons are always being knocked off the top of Earth’s atmosphere as described in Note #1. Although solar storms are not required for this process, solar storms can help. For instance, when a CME strikes Earth’s magnetosphere, the contents of the magnetosphere become extra-energized. Lots of particles furiously strike the top of Earth’s atmosphere, liberating even more electrons than usual. Earth’s electron beams can thus become super-charged. When the storm subsides, the electron beams may weaken, but they never vanish because even the quiet sun produces solar wind. References: Zhang, X., Angelopoulos, V., Artemyev, A. V., Zhang, X.-J. (2021), Beam-driven ECH waves: A parametric study, Phys. Plasmas, 28, 072902, https://doi.org/10.1063/5.0053187 Zhang, X., Angelopoulos, V., Artemyev, A. V., Zhang, X.‐J., Liu, J. (2021). Beam‐driven electron cyclotron harmonic waves in Earth’s magnetotail. Journal of Geophysical Research: Space Physics, 126, e2020JA028743. https://doi.org/10.1029/2020JA028743s https://spaceweatherarchive.com/2021/09/20/earth-can-makes-its-own-auroras/ Solar Cycle 25 continues to overperform. Sunspot counts for Sept. 2021 were the highest in more than 5 years. And, for the 11th month in a row, the sunspot number has significantly exceeded the official forecast. The plot above shows sunspot counts vs. time. The red curve traces the forecast issued by the NOAA/NASA Solar Cycle 25 Prediction Panel in 2019. It calls for a relatively weak solar cycle peaking in July 2025. The sun has a mind of its own, though. Higher-than-expected sunspot counts suggest a stronger cycle, with a peak occurring in late 2024 instead of mid-2025. This is good news for aurora watchers, but maybe not so good for the Internet. https://spaceweather.com/ |
QUICK INFO
Author:
_Messenger Spirit This section is for interesting items which are brought to my attention but which do not merit a separate article.
I welcome your comments, questions or suggestions on any topics you wish to contribute to this section. Please submit these on the Contact and Feedback Form PLEASE DO NOT SUBMIT COMMENTS ON THE FORM WHICH APPEARS UNDER ITEMS ON 'QUICK INFO'; THIS SYSTEM IS NOT WORKING. Categories
All
Archives
April 2024
|