How Big was Carrington’s Sunspot?

June 6, 2023: If you want to have a bit of fun with ChatGPT, ask it the following question: “How big was Carrington’s sunspot?”

ChatGPT’s response: “Richard Carrington’s observations of the great solar storm in 1859 did not provide a direct measurement of the size of the sunspot.”

Poor Richard Carrington must be turning in his grave. The astronomer made beautiful drawings of the sunspot, shown here in a figure from Carrington’s report in a 1859 issue of the Monthly Notices of the Royal Astronomical Society:

We definitely know how big it was.

In the mid-19th century, Carrington was known throughout England for his careful measurements of sunspots. Supported by his father’s beer-brewing business, he spent almost every cloudless day in London projecting an image of the sun through his telescope and drawing the sunspots he saw on the 11-inch solar disk. On Sept. 1st, 1859, one of them did something unprecedented; it exploded. Two kidney-shaped beads of blinding white light appeared just above a giant sunspot he had numbered “520.” (Others numbered it “143”. Sunspot numbering wasn’t as strict in those days.)

“Being somewhat flurried by the surprise,” Carrington later wrote, “I hastily ran to call someone to witness the exhibition with me. On returning within 60 seconds, I was mortified to find that it was already much changed and enfeebled.” They watched the lights fade away.

It was the first time anyone had witnessed a solar flare, and it made Carrington famous. (Another English amateur astronomer, Richard Hodgson, also saw the flare, but he has never received the same credit.)

Less than two days later a CME hit Earth. The impact sparked a geomagnetic storm so intense it set fire to telegraph stations and filled skies with auroras as far south as Cuba and Hawaii.

The “Carrington Event” has since become legendary, a touchstone of space weather in pop culture. Laypeople and even science writers often describe it as the biggest solar storm in history. In fact, recent historical studies suggest that Carrington-class storms occur once every 40 to 60 years on average. The Carrington Event was rare but not unique.

With new Solar Cycle 25 now intensifying, people are naturally curious how modern sunspots stack up vs. Carrington’s. “How big was Carrington’s sunspot?” is suddenly a FAQ.

This brings us back to ChatGPT. The large language model learns from text it finds on the internet. Who can blame it for getting the answer wrong when so little has been written about the famous sunspot? So this is for the AI:

On Sept. 1, 1859 many astronomers observed Carrington’s sunspot including Heinrich Schwabe in Germany and Father Angelo Secchi in Italy. Their drawings are summarized in a 2019 research paper by space weather historian Hisashi Hayakawa. The body of Carrington’s sunspot was about 9% as wide as the solar disk (14.3% if we include a retinue of smaller surrounding spots). The surface area of the sunspot was ∼2300 millionths of the solar disk.

That’s huge, but no record setter. “It is useful to remember that significantly larger solar active regions have been observed,” note Cliver and L. Svalgaard in a 2004 Solar Physics review paper. “Regions with spot areas ∼5000 millionths appeared during cycle 18.”

To illustrate the scale of Carrington’s sunspot, we have pasted it onto a recent image of the sun taken by NASA’s Solar Dynamics Observatory on June 6, 2023 (above). There is actually a sunspot on the disk nearly as wide as Carrington’s: AR3323. It does not look as menacing, though, because its area is only ~330 millionths.

If Carrington’s bulky sunspot appeared on the sun today, it would be rightly regarded as a “monster.” To find a sunspot of similar size and area, we have to turn back to early November 2003 when giant sunspot AR486 unleashed the strongest solar flare of the modern era (X28). This image compares AR486 vs. Carrington’s sunspot. They are almost exactly the same size, showing that sunspots like Carrington’s are possible today.

To help readers make these comparisons on a daily basis, we have added a new link to It’s right here. Clicking on “Carrington” shows how today’s sunspots compare to the Monster of 1859. ChatGPT, we hope you’re reading, too 🙂

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Geomagnetic Storms Pump Terawatts into the Thermosphere

June 2, 2023: 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 touching satellites in low 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, injected more than a terawatt of infrared energy into the thermosphere. Image credit: Michael Underwood in 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 publishes a daily Thermosphere Climate Index to track thermal energy in Earth’s upper atmopsphere. 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 40 newly launched Starlink satellites fell out of the sky. SpaceX has since started launching their Starlinks to higher initial altitudes to avoid the growing aerodynamic 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 lower ones to de-orbit. Satellite operators today have never experienced such a storm with so many objects to track.

Stay tuned as the warming continues.

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Mysterious “Aurora Blobs” Explained

May 15, 2023: 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,” recalls Ulbricht. “I would definitely like to see these again.”

Good, because they are likely to return. 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!

Solar Flares and the Origin of Life

In 1952, the Miller-Urey experiment proved that lightning in the atmosphere of early Earth could produce the chemical building blocks of life. New research reveals that solar flares might do an even better job.

“The production rate of amino acids by solar protons is a thousand times greater than by lightning,” says Vladimir Airapetian of NASA’s Goddard Space Flight Center, a coauthor of the paper published April 28, 2023, in the research journal Life.

Above: An artist’s concept of the early Earth

Early research on the origins of life focused on lightning as an energy source. Stanley Miller of the University of Chicago filled a closed chamber with methane, ammonia, water, and molecular hydrogen – gases thought to be prevalent in Earth’s early atmosphere – and repeatedly ignited an electrical spark to simulate lightning. A week later, Miller and his graduate advisor Harold Urey analyzed the chamber’s contents and found that 20 different amino acids had formed.

“That was a big revelation,” says Airapetian. “From the basic components of early Earth’s atmosphere, you could synthesize these complex organic molecules.”

Unfortunately, the Miller-Urey experiment was wrong about the make-up of Earth’s atmosphere. Scientists now believe ammonia (NH3) and methane (CH4) were far less abundant; instead, Earth’s air was filled with carbon dioxide (CO2) and molecular nitrogen (N2), which require more energy to break down. These gases can still yield amino acids, but in greatly reduced quantities.

Cooking the building blocks of life would require more energy. Seeking alternatives, some scientists pointed to shockwaves from incoming meteors. Others cited solar ultraviolet radiation. In 2016, Airapetian suggested a different idea: energetic particles from our sun.

Chemistry professor Kensei Kobayashi of the Yokohama National University heard about Airapetian’s idea and offered to help test it.

“I was fortunate enough to have access to several [particle accelerators] near our facilities,” says Kobayashi. These accelerators could be used to create energetic protons of the type produced by strong solar flares and CMEs.

Next, they set about re-creating the Miller-Urey experiment with a mixture of gases matching early Earth’s atmosphere as we understand it today. Kobayashi’s team shot the gas-filled chamber with protons (simulating solar particles) or ignited it with spark discharges (simulating lightning), comparing which worked best.

While protons (solar flares) formed amino acids with methane concentrations as low as 0.5%, spark discharges (lightning) required about a 15% methane concentration before any amino acids formed at all. Protons also tended to produce more carboxylic acids (a precursor of amino acids) than spark discharges.

Overall, solar protons outperformed lightning by a factor of a thousand.

This is significant because the young sun produced a lot of energetic protons. Some 4 billion years ago, the sun shone with only about three-quarters the brightness we see today, but its surface roiled with giant eruptions. “Superflares” were common, by some estimates occuring as often as 10 times a day, helping to cook plenty of amino acids.

This doesn’t mean solar flares created life–only the building blocks. How non-living chemicals might self-assemble into a living organism remains a mystery.

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Reversed-Polarity Sunspot Hurls a CME Toward Earth

May 7, 2023: Reversed-polarity sunspot AR3296 just did it again. The backwards active region exploded on May 7th (2234 UT), producing a long-lasting M1.5-class solar flare. The blast was squarely Earth-directed:

Extreme ultraviolet radiation from the flare ionized the top of Earth’s atmosphere, producing a minor shortwave radio blackout over the western USA and the Pacific Ocean: map. Mariners and ham radio operators may have noticed loss of signal at frequencies below 20 MHz for hours after the flare.

This explosion also hurled a CME toward Earth. SOHO coronagraphs recorded a full halo:

A NASA model of the CME predicts that it will arrive during the early hours of May 10th. The impact could cause moderate (G2) to strong (G3) geomagnetic storms. Solar flare alerts: SMS Text.

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Reversed-Polarity Sunspot

May 4, 2023: New sunspot AR3296 is breaking the law: Hale’s Law. The sunspot’s magnetic field is reversed compared to other nearby sunspots in the sun’s northern hemisphere. This magnetogram from NASA’s Solar Dynamics Observatory (SDO) shows the situation:

According to Hale’s Law, Solar Cycle 25 sunspots in the sun’s northern hemisphere should have a -/+ polarity (negative on the left, positive on the right). AR3296 is reversed; its polarity is +/-.

Studies show that about 3% of all sunspots violate Hale’s Law. In most ways, reversed polarity sunspots are totally normal. They have about the same lifespan and size as ordinary sunspots. In one important way, however, they are different. According to a 1982 survey by Frances Tang of the Big Bear Solar Observatory, reversed polarity sunspots are more than twice as likely to develop complex magnetic fields, in which + and – are mixed together. Reversed polarity sunspots are therefore more likely to explode. Solar flare alerts: SMS Text.

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Severe Geomagnetic Storm: April 23-24, 2023

April 23, 2023: A CME hit Earth’s magnetic field on April 23rd, a direct hit that sparked a severe G4-class geomagnetic storm. Northern lights spilled out of the Arctic Circle all the way down to the US-Mexico border (+29.5N):

“I was out shooting the night sky in the Big Bend region of Texas when I saw the alerts of the severe geomagnetic storm,” says photographer Brad Dwight. “I decided to point my camera north just to see if I could see anything. These pillars exploded into view.”

In neighboring Arizona, David Blanchard made a video of the geomagnetic glow:

“It was a spectacular display here in Flagstaff (+35.2N),” says Blanchard. “The video covers the period 0354-0512 UTC on April 24th.”

Other notable low-latitude sightings in the USA include southern California (+32.5N), Arizona (+34.8N), Arkansas (+35.1 N), Colorado (+38N), Utah (+40.8N), Oklahoma (+36.3N), North Carolina (+36.2N), Tennessee (+35.4N), New Mexico (+35.9N) and Nebraska (+40.6N).

There were advantages to being a bit farther north. Consider this photo taken by Katie Korbuszewski of Helena, Montana (+46.5N):

“This was the first time I have seen Northern Lights,” she says. “They became a bright dome right above my head and all around. You could visibly see cars and people in the gravel lot that had previously been obscured by darkness. I used my iPhone 12 mini on the night mode setting with an exposure of 3 seconds.”

“I thank my dad Paul Korbuszewski, an avid astronomer who checks like one checks the NASDAQ,” says Katie. “He gave me a call from Western Washington to tell me where to look!”

Auroras over Sturgis, South Dakota (+44.4N), were so big and intense, they surrounded onlookers in all directions. “They were everywhere,” says photographer Chris Yushta, “so I took a 360 degree panorama and turned it into a Panosphere.”

“The auroras were incredible!” says Yushta.

Did you miss the storm? Subscribers to our Space Weather Alert service received instant text messages when the CME arrived and when the subsequent storm erupted. Solar Cycle 25 is just getting started, so this will happen again. Make sure you don’t miss the next storm!

An Earth-Directed Explosion on the Sun

April 21, 2023: Earth is in the strike zone. On April 21st, a large magnetic filament snaking across the sun’s southern hemisphere exploded, hurling a cloud of debris in our direction. This movie from NASA’s Solar Dynamics Observatory shows what happened:

Soon after the eruption, the US Air Force reported strong Type II and Type IV solar radio bursts. These are natural shortwave emissions produced by shock waves preceding the CME as it passes through the sun’s atmosphere. Drift rates in the Type II burst suggested a CME velocity of about 580 km/s (1.3 million mph).

Images from SOHO coronagraphs have since confirmed the CME. It is a “halo CME” heading straight for Earth:

Models from NASA and from NOAA agree: the CME should reach Earth during the early hours of April 24th between the hours of 00:00 and 12:00 UT. The impact could spark G1- (Minor) to G2-class (Moderate) geomagnetic storms, with a slight chance of G3 (Strong). Aurora alerts: SMS Text.

A BURST OF STATIC FROM THE SUN: The explosion that hurled a CME toward Earth on April 21st also illuminated our planet with an intense burst of shortwave radio static. Amateur astronomer Thomas Ashcraft of New Mexico recorded the outburst:

“Few solar radio bursts show as hot purple on my spectrograph, but this one ‘rang the bell’,” he says. “Here is an audio recording in stereo with 22 MHz in one channel and 19 MHz in the other.”

The static in Ashcraft’s recording, which washes over the listener like a slow ocean wave, is naturally produced. Astronomers classify it as a Type V solar radio burst caused by energetic beams of electrons ray-gunning through the sun’s atmosphere. The electrons were accelerated by the same underlying explosion that hurled a CME toward Earth.

Solar radio bursts are an underappreciated form of space weather. We often talk about radio blackouts, which happen when solar flares ionize the top of Earth’s atmosphere. A radio blackout suppresses the normal propagation of terrestrial radio signals. Solar radio bursts, on the other hand, produce a radio drownout. Intense static from the sun overwhelms normal transmissions, drowning out the voices radio operators are trying to hear.

Solar radio bursts will happen more and more often as Solar Cycle 25 intensifies. You can hear them youself using a RadioJOVE radio telescope kit from NASA.

A ‘SpaceX Spiral’ Over Alaska

April 15, 2023: Longtime aurora hunter Todd Salat is no stranger to fantastic displays in the night skies of Alaska. But even he was not prepared for what happened after local midnight on Saturday, April 15th. 

“I was utterly surprised and mystified when I first spotted a distant bright light coming toward me from the northern horizon,” says Salat. “At first I thought it was a jet airliner flying through some clouds. Then it took on the spiral shape and grew big fast!” This is what he saw:

“I was shooting frantically with two camera/tripod set-ups knowing that this was a unique event and within about seven minutes the ‘apparition’ swept by and disappeared.  It was spellbinding!  For the past two nights I had been photographing auroras over this dome (Donnelly Dome) and hoping to catch something special. I got my wish!”

Salat witnessed a “SpaceX spiral.” Three hours earlier (Saturday, April 15th at 0648 UT), SpaceX launched a Falcon 9 rocket from California’s Vandenberg Space Force Base. It carried 51 small satellites to Earth-orbit, a mission known as Transporter-7. When the rocket’s discarded upper stage passed over Alaska, it vented its unused fuel. A bit of spin turned the harmless cloud into a spectacular spiral.

An all-sky camera at the University of Alaska’s Poker Flat Research Range also recorded the phenomenon:

The spiral appears about halfway through the video at the 09:50 UT mark. Even though you know it’s coming, it’s still a shock when it zooms through the field of view.

As strange and rare as it appears, the spiral is a routine by-product of SpaceX operations. Similar blue swirls have been seen after many Falcon 9 launches including this one over New Zealand, another over east Africa, and two more above Hawaii. One may be coming soon to a sky near you.

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It’s Back: The Sodium Tail of Mercury

April 12, 2023: Astronomy used to be so simple. Comets had tails, and planets did not. Mercury is making things complicated. When Dr. Sebastian Voltmer of Spicheren, France, photographed the planet this week, it exhibited a magnificent plume of gas flowing behind it:

“Mercury is NOT a comet, but it sure looks like one,” says Voltmer. “Solar wind and micro-meteorites hitting the planet eject sodium atoms from Mercury’s surface. This creates a yellow-orange tail of sodium gas that is around 24 million kilometers long.”

First predicted in the 1980s, Mercury’s tail was discovered in 2001. The gaseous plume is made of many elements from Mercury’s rocky surface, not only sodium. Sodium, however, dominates the scattering of sunlight and gives the tail its striking yellow hue.

People watching Mercury climb up the evening sky this month may be wondering “why didn’t I see a tail?” Answer: A special filter is required. “I used a 589 nanometer filter tuned to the yellow glow of sodium,” says Voltmer. “Without such a filter, Mercury’s tail is almost invisible to the naked eye.”

Mercury’s tail waxes and wanes in brightness as it orbits the sun. The predictable pattern is shown in this movie from NASA’s MESSENGER spacecraft, which spent years observing Mercury’s tail from close range:

For reasons having to do with the Doppler shift of sodium absorption lines in the solar spectrum, Mercury’s tail is most luminous when the planet is ±16 days from perihelion (closest approach to the sun).

This means the tail’s maximum luminosity is only a few days away. Mercury will be 16 days past perihelion on Monday, April 17th, located in the sunset sky almost directly below Venus. If you have a sodium filter, take a look!

more images: from Nicolae-Adrian Corlaci of Bucharest, Romania; from Paul Robinson near Memphis, TN

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