In a joint statement on Oct. 15th, NASA and NOAA announced that Solar Maximum is underway. If you saw last week's geomagnetic storm, you probably reached the same conclusion. Good news: Solar Max is not a narrow moment in time; it is a lengthy phase of solar activity that can last for 2 or 3 years. More aurora outbursts are likely in 2024 and 2025. Listen to the press conference here.
https://spaceweather.com/

Confirmed: Two CMEs are now heading for Earth following consecutive X-flares (X7.1 and X9.1) from active sunspot AR3842. According to NOAA and NASA models, the first will strike Earth on Oct 4th and the second (more potent) will strike on Oct. 6th. The dual impacts could spark strong G3-class geomagnetic storms with auroras at mid-latitudes, especially on Oct. 6th.
https://spaceweather.com/

The historic geomagnetic storm of May 10-11, 2024, produced auroras across Europe, Asia, Mexico, and all 50 US stetes--even Hawaii. Hundreds of millions of people saw the colored lights for the first time in their lives, with photographers catching shots they couldn't have previously imagined. For instance, here is Opuntia chlorotica surrounded by the red glow of a CME:

Kyle Nulla Cognomen sends this picture from Las Vegas, Nevada. "What a gorgeous view of the desert sky illuminated by aurora," he says. "I could see the reds and greens with my naked eye!"
Our photo gallery is filled with unusual images like this one--auroras in strange places, illuminating cactii, palm trees, pyramids, and Carribean beaches. There's no way to pick a favorite. Or is there? Browse the gallery to explore the extraordinary global display.
https://spaceweather.com/

NOAA forecasters say that the storm is really over now. There's no chance of additional G5 activity this week because all the big CMEs have already come and gone. However, relatively minor G1 or G2-class storms are possible on May 13th in response to a glancing blow from this off-target CME.

This morning, May 13th, giant sunspot AR3664 issued a parting shot from the edge of the Earth strike zone. An M6-class flare at 0944 UT hurled an impressive CME into space:

Unlike most of the sunspot's previous CMEs, this one is not going to hit Earth with bullseye precision. Instead, it is expected to deliver a glancing blow on May 15th or 16th. The impact could spark minor (G1) to moderate (G2) geomagnetic storms.
https://spaceweather.com/

Giant sunspot AR3664 unleashed another X-flare today (May 11th @ 0139 UT)--its strongest yet. NASA's Solar Dynamics Observatory captured a bright ultravolet flash from the category X5.8 explosion:

Radiation from the flare caused a deep shortwave radio blackout over the Pacific Ocean. Ham radio operators and mariners may have noticed loss of signal at frequencies below 30 MHz for as much as an hour after the flare's peak.
We don't yet know if this flare hurled a CME into space. If it did, it could have a grazing Earth-directed component. Confirmation awaits fresh data from SOHO coronagraphs.
https://spaceweather.com/

The first of six CMEs hurled toward Earth by giant sunspot AR3664 hit our planet's magnetic field today. The impact on May 10th at 1645 UT jolted magnetometers around the world and sparked a severe (G4-class) geomagnetic storm. This storm is underway now. More CMEs are following close behind and their arrival could extend the storm into the weekend. Sign up for Space Weather Alerts to receive instant text messages when the CMEs arrive.
The ongoing storm is producing low-latitude auroras in the southern hemisphere. Ken James sends this picture from the Snake Valley Observatory in Victoria, Australia:

"The red, yellow and green colours were easily visible to my naked eye," says James.
Readers in the USA should note that the southern latitude of Victoria, Australia, 37 degrees, is the same as the northern latitude of central California. That's how far down auroras could be seen if it were dark instead of daylight in North America.
Why is this storm so severe? Take a look at the solar wind data from NOAA's DSCOVR spacecraft:

After the CME struck, the speed of the solar wind blowing around our planet abruptly increased to more than 700 km/s. More importantly, south-pointing magnetic fields from the sun washed over the Earth, opening a crack in our planet's magnetosphere. Solar wind poured through the gap to turbo-charge the storm.
https://spaceweather.com/

No. AR3664 is indeed a 'Carrington-class' sunspot, but the CMEs it hurled toward Earth over the past few days are not as potent as the monster CME of Sept. 1, 1859. NOAA says we might experience a severe geomagnetic storm when the CMEs arrive this weekend. If geomagnetic storms were hurricanes, 'severe' would be category 4. The Carrington Event was category 5 or greater. So this is no Carrington Event. Even so, category 4 is pretty intense--if it happens. Stay tuned for some great auroras!

Great sunspot AR3664 has hurled an astonishing five CMEs toward Earth. They're all in this frenetic 2-day coronagraph movie from the Solar and Heliospheric Observatory (SOHO):

The two bright objects are Jupiter (left) and Venus (right). The CMEs will miss those planets and hit Earth instead.
According to a NOAA forecast model, the first three CMEs could merge for form a "Cannibal CME." Cannibal CMEs form when fast-moving CMEs overtake and gobble up slower CMEs in front of them. Internal shock waves created by such CME collisions do an good job sparking geomagnetic storms when they strike Earth's magnetic field.
The Cannibal CME is expected to arrive on May 11th. It alone could spark a strong (G3) geomagnetic storm. With two more CMEs following close behind, storm levels could become extreme (G4), sparking auroras at mid- to low-latitudes across Europe and the USA.
https://spaceweather.com/

NOAA models confirm that a Cannibal CME will strike our planet on Dec. 1st. Cannibal CMEs form when a fast CME sweeps up a slower CME ahead of it. The combination contains intense, tangled magnetic fields that can do a good job sparking auroras when they reach Earth. If a Cannibal CME strikes Earth on Dec. 1st, as predicted, geomagnetic storm levels could reach category G3 (Strong). If so, here's what we can expect. The last G3-class storm on Nov. 5th sparked not only bright auroras, but also deep-red SAR arcs around the world. Greg Redfern photographed this example from the Shenandoah National Park in Virginia:

"I didn't realize I had photographed an SAR arc until I processed my images the next day, stitching two of them together to reveal its shape," says Redfern.
SAR arcs look like auroras, but they are not. They are the glow of heat energy leaking into the upper atmosphere from Earth's ring current system–a donut-shaped circuit carrying millions of amps around our planet. During the Nov. 5th geomagnetic storm, these red arcs were observed as far south as Texas and California.
Auroras were observed as well -- "and they were INSANE," says Janne Maj Nagelsen, who watched the display from Stamnes, Vaksdal, Norway:

"I have never seen such strong auroras," says Nagelsen. "Not to mention the colors. I mean look at the picture! They were totally, literally insane."

Auroras are caused by charged particles raining from space down upon Earth's atmosphere. Unlike SAR arcs, which are pure red, auroras can have a rich and stunning variety of colors. Both phenomena may be photographed on Dec. 1, 2023, when a Cannibal CME is expected to hit Earth.
https://spaceweather.com/

Europeans are still trying to wrap their minds around what happened after sunset on April 23, 2023. Everyone knew that a CME was coming; photographers were already outside waiting for auroras. But when the auroras appeared, they were very strange."I had never seen anything quite like it," says Heiko Ulbricht of Saxony, Germany. "The auroras began to tear themselves apart, pulsating as they formed individual blobs that floated high in the sky."

"It literally took my breath away," he says. "My pulse was still racing hours later!" The same blobs were sighted in France and Poland, and in Denmark they were caught flashing like a disco strobe light.  Ordinary auroras don't act like this.

Indeed, "these were not ordinary auroras," confirms space physicist Toshi Nishimura of Boston University. "They are called 'proton auroras,' and they come from Earth's ring current system."

Most people don't realize that Earth has rings. Unlike Saturn's rings, which are vast disks of glittering ice, Earth's rings are invisible to the naked eye. They are made of electricity--a donut-shaped circuit carrying millions of amps around our planet. The ring current skims the orbits of geosynchronous satellites and plays a huge role in determining the severity of geomagnetic storms.

Sometimes during strong geomagnetic storms, protons rain down from the ring system, causing a secondary shower of electrons, which strike the atmosphere and make auroras. Earth-orbiting satellites have actually seen these protons on their way down. Ordinary auroras, on the other hand, are caused by particles from more distant parts of Earth's magnetosphere and have nothing to do with Earth's ring current.Mystery solved? Not entirely. "We still don't know why proton auroras seem to tear themselves apart in such a dramatic way," says Nishimura. "This is a question for future research."

"It was very exciting to watch," says Ulbricht. "I definitely want to see them again."

Good, because they'll be back. Solar Cycle 25 ramping up to a potentially-strong Solar Maximum next year. Future storms will surely knock more protons loose from the ring current system.

Here's what to look for: (1) Proton auroras tend to appear around sunset. Why? Electric fields in Earth's magnetosphere push the protons toward the dusk not dawn side of our planet. (2) Proton auroras love to pulse--a sign of plasma wave activity in Earth's ring current. (3) Proton auroras are sometimes accompanied by deep red arcs of light (SARs), the glow of heat leaking from the ring current system. These red arcs were also seen on April 23rd.

Solar Max is coming. Let the proton rain begin!
https://spaceweather.com/

Last month, during the late hours of April 23rd, a CME hit Earth's magnetic field. The impact sparked a severe geomagnetic storm with auroras so bright they could be seen as far south as Texas. Invisible to the human eye, something else happened. There was a sudden decrease in cosmic radiation:

In a matter of hours, cosmic rays peppering Earth's atmosphere dropped to their lowest levels since 2015. Neutron monitors in Oulu, Finland, detected the drop, which lasted for days.
This is called a "Forbush decrease," named after American physicist Scott Forbush who studied cosmic rays in the early 20th century.  It happens when a coronal mass ejection (CME) sweeps past Earth and pushes galactic cosmic rays away from our planet. It sounds counterintuitive, but big solar storms can cause sharp decreases in space radiation.
This Forbush decrease is over, but more are in the offing. Solar Max is coming and soon the sun will be hurling many more CMEs in our direction. Their cumulative effect could create a sustained decrease in cosmic radiation, lowering dose rates for astronauts and air travelers. Stay tuned for updates.
https://spaceweather.com/

Chinese astrophotographer Jeff Dai has long dreamed of seeing auroras over his home country. "On April 24th, my dream came true," he says. A severe geomagnetic storm was underway when he drive to the countryside outside Karamay, Xinjiang, China, and photographed a sky full of Northern Lights:

"I could see them with my naked eye," he says. "It was truly spectacular!"
But there's more to the story. Only a fraction of the lights he saw were actual auroras. Note the red arc at the top of his photo. That's something else--an "SAR."
SARs are red arcs of light that ripple across the sky during some geomagnetic storms. They were discovered in 1956 at the beginning of the Space Age. Researchers didn’t know what they were and unwittingly gave them a misleading name: "Stable Auroral Red arcs" or SARs.
In fact, SARs are neither stable nor auroras. Auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow like the picture tube of an old color TV. SARs form differently. They are a sign of heat energy leaking into the upper atmosphere from Earth’s ring current system--a donut-shaped circuit of plasma carrying millions of amps around our planet.

SARs are among the reddest things in the sky, with a monochromatic glow at 6300 Å that comes from atomic oxygen in the upper atmosphere. The human eye is relatively insensitive to light at this wavelength, but cameras record the color easily. Pro tip for photographers: Use a 6300 Å filter.
"Seeing auroras from China is very difficult," says Dai. "It happens maybe 1-2 times every 11 years." Seeing an SAR is even more rare. It was a dreamy night, indeed.
www.spaceweather.com

MINOR GEOMAGNETIC STORM WATCH: NOAA forecasters say that minor G1-class geomagnetic storms are likely on March 26th as Earth passes through a stream of high-speed solar wind. The gaseous material is flowing from a large hole in the sun's atmosphere. Arctic sky watchers should be alert for auroras.
SEVERE GEOMAGNETIC STORM: On March 23-24, auroras spread into the United States as far south as New Mexico (+32.8N) during a severe (category G4) geomagnetic storm--the most intense in nearly 6 years. The cause of the storm is still unclear; it may have been the ripple effect of a near-miss CME on March 23rd.
"For about 30 minutes we watched as auroras danced and simmered in the sky above Yellowstone National Park", says Michael Underwood, who photographed the light show from the Mammoth Hot Springs at latitude +45 degrees:

"This was my first time seeing the aurora and hopefully not the last", he says. "It was a truly unbelievable sight."
Other notable mid- to low-latitude sightings were made in Virginia (+38.7N), Colorado (+40.4N), Missouri (+40.2N), Colorado again (+40.6N), Nebraska (+42.4N), Nebraska again (+41N) and North Carolina (+36.2N). More than half of all US states were in range of the display.
Not every light in the sky was the aurora borealis. There was also STEVE. Alan Birdsell photographed the phenomenon from Spokane, Washington:

"This was the first time I have seen a severe geomagnetic storm here in Spokane," says Birdsell. "It was all a very profound and surreal experience."
STEVE (Strong Thermal Emission Velocity Enhancement) looks like an aurora, but it is not. The phenomenon is caused by hot (3000°C) ribbons of gas flowing through Earth’s magnetosphere at speeds exceeding 6 km/s (13,000 mph). These ribbons appear during strong geomagnetic storms, revealing themselves by their soft purple glow. STEVE also appeared over South Dakota, Washington State, Idaho, Idaho again, Montana, Montana again, and Scotland.
This remarkable and surprising storm began on March 23rd when magnetic fields in the space around Earth suddenly shifted. In the jargon of space weather forecasting "BsubZ tipped south". South-pointing magnetic fields can open a crack in Earth's magnetosphere and indeed that's what happened. Earth's "shields were down" for almost 24 hours, allowing solar wind to penetrate and the storm to build to category G4.
These developments may have been caused the close passage of an unexpected CME. The storm cloud could have left the sun on March 20-21 when SOHO coronagraph data were unusually sparse. We didn't know it was coming. For aurora watchers, it was a welcome surprise.
www.spaceweather.com

Pink auroras are rare. Pulsating auroras are rare, too. Last night in Abisko, Sweden, sky watchers witnessed both rarities at the same time. Hit PLAY to make the sky pulse:

"My guides who photographed the display couldn't believe their eyes," says Chad Blakley, the owner of Lights over Lapland. "They are all saying things like 'I have never seen anything like this before!' and one of them described it as 'a glitch in the Matrix.'"
Pulsating auroras are Blakley's favorite: "The best way to describe a pulsating aurora is to imagine the sky as a large checker board," he says. "As the pulsating begins, black squares on the board would illuminate as a green aurora. Then, in an instant, all the black squares lose their illumination and the red squares on the imaginary checkerboard immediately glow green."
In this case, however, the green was pink. Pink auroras appear when solar wind particles penetrate unusually deep in Earth's atmosphere, striking nitrogen molecules less than 100 km above our planet's surface. A crack in Earth's magnetic field on Oct. 3rd let the particles reach that level.
Pulsating auroras are so mysterious, NASA keeps launching rockets into them to learn what makes them tick. In 2018, researchers led by S. Kasahara of the University of Tokyo conclusively linked pulsating auroras to "chorus waves" in Earth's magnetosphere. Their findings explain everything -- except the shape of the 'squares' and why they blink so quickly. Keep launching rockets, NASA.
www.spaceweather.com

September 20, 2021 / Dr.Tony Phillips - NASA

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/