The Termination Event has Arrived

Feb. 26, 2022: Something big just happened on the sun. Solar physicists Scott McIntosh (NCAR) and Bob Leamon (U. Maryland-Baltimore County) call it “The Termination Event.”

“Old Solar Cycle 24 has finally died–it was terminated!” says McIntosh. “Now the new solar cycle, Solar Cycle 25, can really take off.”

The “Termination Event” is a new idea in solar physics, outlined by McIntosh and Leamon in a December 2020 paper in the journal Solar Physics. Not everyone accepts it–yet. If Solar Cycle 25 unfolds as McIntosh and Leamon predict, the Termination Event will have to be taken seriously.

Above: Predictions for Solar Cycle 25. Blue is the “official” prediction of a weak cycle. Red is a new prediction based on the Termination Event.

The basic idea is this: Solar Cycle 25 (SC25) started in Dec. 2019. However, old Solar Cycle 24 (SC24) refused to go away. It hung on for two more years, producing occasional old-cycle sunspots and clogging the sun’s upper layers with its decaying magnetic field.  During this time, the two cycles coexisted, SC25 struggling to break free while old SC24 held it back.

“Solar Cycle 24 was cramping Solar Cycle 25’s style,” says Leamon.

Researchers have long known that solar cycles can overlap. The twist added by McIntosh and Leamon is the realization that overlapping cycles interact. This makes sense. In the early 20th century, George Ellery Hale discovered that the magnetic polarity of sunspot pairs reverses itself from one cycle to the next; indeed, the sun’s entire global magnetic field flips every ~11 years. When adjacent, opposite-polarity solar cycles overlap, they naturally interfere.

Termination Events mark the end of interference, when a new cycle can break free of the old.

Above: Bands of coronal bright points (hot spots in the sun’s atmosphere) linked to old Solar Cycle 24 vanished in Dec. 2021, signalling a Termination Event. A Twitter thread from Scott McIntosh explains this in greater detail.

The timing of the Termination Event can predict the intensity of the new cycle. In their Solar Physics paper, McIntosh and Leamon looked back over 270 years of sunspot data and found that Termination Events happen every 10 to 15 years.

“We found that the longer the time between terminators, the weaker the next cycle would be,” explains Leamon. “Conversely, the shorter the time between terminators, the stronger the next solar cycle would be.”

So when did the latest Termination Event happen? Dec. 2021. This yields a specific, testable prediction for Solar Cycle 25.

“We have finalized our forecast of SC25’s amplitude,” says McIntosh. “It will be just above the historical average with a monthly smoothed sunspot number of 190 ± 20.”

“Above average” may not sound exciting, but this is in fact a sharp departure from NOAA’s official forecast of a weak solar cycle. It could be just enough to catapult Terminators into the forefront of solar cycle prediction techniques.

Stay tuned. We’ll be back.

Huge Explosion on the Farside of the Sun

Feb. 17, 2022: New images from the Solar and Heliospheric Observatory (SOHO) are giving us a better look at yesterday’s farside explosion. SOHO coronagraphs recorded the most dramatic CME in years:

No, there won’t be a geomagnetic storm. The explosion happened on the farside of the sun, so the CME is heading away from Earth. We dodged a bullet.

Some readers have asked “How strong was the underlying solar flare?” We don’t know. Solar flares are classified by their X-ray output, but there are no spacecraft on the farside of the sun with X-ray sensors. Best guess: It was an X-flare.

You might suppose that the farside of the sun is hidden from view. However, researchers using a technique called “helioseismology” can make crude maps of the sun’s hidden hemisphere. Their latest map reveals a huge farside active region:

The black blob is a sunspot group–a big one–and it is the likely source of the explosion. According to Junwei Zhao of Stanford University’s helioseismology group, active regions this large are rare. “This is only the second farside active region of this size since September 2017,” he says.

Lucas Guliano, a solar scientist at the Harvard-Smithsonian Center for Astrophysics, believes the active region might be an old friend: AR2936, a sunspot that was on the Earthside of the sun in early February.

“If so, it is the same sunspot responsible for the geomagnetic storm that downed the SpaceX satellites on Feb. 4th,” he says.

Apparently it has grown since then. Based on its current location, the sunspot could emerge into view over the sun’s northeastern limb about 4 days from now. It could be quite a sight, so stay tuned. Solar flare alerts: SMS Text.

The Starlink Incident

Feb. 9, 2022: As many as 40 Starlink satellites are currently falling out of the sky–the surprising result of a minor geomagnetic storm. SpaceX made the announcement yesterday:

“On Thursday, Feb. 3rd at 1:13 p.m. EST, Falcon 9 launched 49 Starlink satellites to low Earth orbit from Launch Complex 39A (LC-39A) at Kennedy Space Center in Florida. … Unfortunately, the satellites deployed on Thursday were significantly impacted by a geomagnetic storm on Friday, [Feb. 4th].”

Two days before launch a CME hit Earth’s magnetic field. It was not a major space weather event. In fact, the weak impact did not at first spark any remarkable geomagnetic activity. However, as Earth passed through the CME’s wake, some sputtering G1-class geomagnetic storms developed. It was one of these minor storms that caught the Starlink satellites on Feb. 4th.

Geomagnetic storms heat Earth’s upper atmosphere. Diaphanous tendrils of warming air literally reached up and grabbed the Starlink satellites. According to SpaceX, onboard GPS devices detected atmospheric drag increasing “up to 50 percent higher than during previous launches.”

“The Starlink team commanded the satellites into a safe-mode where they would fly edge-on (like a sheet of paper) to minimize drag,” says SpaceX. “Preliminary analysis show the increased drag at the low altitudes prevented the satellites from leaving safe-mode to begin orbit raising maneuvers, and up to 40 of the satellites will reenter or already have reentered the Earth’s atmosphere.”

The Sociedad de Astronomia del Caribe apparently caught one of the reentries over Puerto Rico on Feb. 7th:

SpaceX says that the deorbiting satellites “pose zero collision risk with other satellites and by design demise upon atmospheric reentry—meaning no orbital debris is created and no satellite parts hit the ground.”

Keep an eye on the night sky this week. You might catch a Starlink satellite burning up overhead. Solar flare alerts: SMS Text.

Solar Cycle 25–A Different Point of View

Feb. 4, 2022: For much of the past year, the space weather community has been buzzing about the strong performance of young Solar Cycle 25 (SC25). Every month, sunspot numbers seem to blow past official predictions. This means we’re about to have a strong Solar Maximum, right?

“Not so fast,” cautions Dr. Ron Turner, an analyst at the ANSER research institute in Virginia. “It may be too early to anticipate a strong solar cycle.”

This graph shows why Turner is skeptical:

Solar Cycle 25 is doing something interesting. It is mimicking old Solar Cycle 24 (SC24). “I took sunspot numbers from the early years of SC24 (the red dashed line) and overlaid them on SC25,” says Turner. “They’re an almost perfect match.”

This is significant because Solar Cycle 24 went on to become the weakest solar cycle in a century. Its hot start did not lead to a strong maximum. Turner isn’t saying that Solar Cycle 25 will likewise be a dud. But, rather, “these early sunspot numbers are not enough to guarantee a strong cycle.”

Déjà vu, anyone?