Sky Spectacle: New Year’s Auroras Ignite from Solar Flares!

Auroras May Illuminate New Year’s Sky Following Solar Outbursts

By Meghan Bartels edited by Lee Billings

The sun is saying goodbye to 2024 with a flourish—or rather several flourishes. Our star generated three intense flares on December 29. In addition, two clouds of material it expelled at high speeds may color Earth’s skies with auroras just as countless terrestrial observers celebrate the new year.

Solar flares are classified by their maximum intensity in x-ray wavelengths, with X-class flares being the most potent bursts. The sun’s activity on December 29 included three of these flares, which took place at 2:18 A.M., 11:14 P.M., and 11:31 P.M. EST, according to a NASA announcement. These eruptions illustrate ongoing turbulence amid what researchers have recognized as the peak of the sun’s current activity cycle, which also produced remarkable auroras as far south as Florida in May and October.

The sun’s 11-year activity cycle is influenced by the magnetic fields that churn on its surface. “Our sun acts as a gigantic magnet, and thus most occurrences on the sun are governed by its magnetism,” states Maria Kazachenko, a heliophysicist at the University of Colorado Boulder and the National Solar Observatory.

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Researchers assess the sun’s activity by tallying the dark sunspots that blemish its surface. Each sunspot harbors a smaller magnetic field—despite sunspots often being the size of Earth. Abrupt shifts in the configuration of a sunspot’s magnetic field, termed magnetic reconnection, can unleash a vast amount of energy, causing a solar flare. However, scientists are still endeavoring to grasp what events can initiate magnetic reconnections.

“The significant challenge with these flares is that we cannot really insert a thermometer or a magnetometer into the solar flare,” Kazachenko indicates. “So it’s quite challenging to comprehend what’s transpiring.”

Moreover, magnetic reconnection in one sunspot may incite the phenomenon in another one—even across considerable distances—in what scientists refer to as a sympathetic eruption. “We often observe flares happening in clusters,” Kazachenko remarks. The two flares that transpired on Sunday evening represented such a cluster: they involved sunspots positioned on opposite sides of the sun’s equator that erupted within less than 20 minutes of each other.

However, flares are simply bursts of radiation. For an aurora to materialize, the sun typically must emit a bubble of plasma known as a coronal mass ejection (CME), a phenomenon that follows some but not all flares. The occurrence of a CME hinges on the intricacies of the magnetic fields in operation. During certain flares, magnetic fields confine material within the sun. In contrast, during others, they permit vast masses of plasma to escape from the tumultuous star. The greater the amount of material, the higher the likelihood of witnessing more stunning auroras, Kazachenko notes.

Regarding Sunday’s events, all three significant flares yielded CMEs. However, it remains uncertain whether they will result in auroras. The National Oceanic and Atmospheric Administration’s Space Weather Prediction Center has issued a geomagnetic storm watch for December 31 and January 1, which it claims could lead to auroras becoming observable over the northern U.S. and extending into the country’s lower Midwest.

The unpredictability in the forecast is attributed to several factors. Only two CMEs are on trajectories that could potentially impact Earth, and these might only result in glancing impacts, complicating predictions regarding their secondary effects. Furthermore, Kazachenko explains, for an aurora to form, the magnetic field of the plasma blob must align oppositely to Earth’s own magnetic field. Otherwise, the plasma will merely pass by, hardly affecting our planet.

The recent activity does not astonish scientists who have been meticulously observing the sun’s journey through its activity cycle. In a press briefing in October, experts declared that the sun is officially at the maximum phase of that cycle and will remain so for a significant portion of 2025.

“We can expect the maximum phase to be extended, approximately three to four years long,” remarked Lisa Upton, a solar scientist at the Southwest Research Institute, during that briefing. “Currently, we are about two years into the maximum period, so we anticipate another year or so of maximum phase before we truly enter the declining stage.”

Throughout the remainder of the solar maximum period and beyond, researchers foresee additional activity and more effects on Earth. “We expect further solar and geomagnetic storms providing chances to observe aurora over the next several months,” stated NASA scientist Kelly Korreck during the same press briefing.

And while solar outbursts can pose risks to satellites and astronauts in orbit as well as to terrestrial power grids, scientists are excited by the activity seen in 2024 and that of this solar cycle, coinciding with the onset of a large new solar telescope and two distinct spacecraft, all aimed at unraveling the mysteries of solar operations.

“This year has been extraordinary,” Kazachenko states. “We’re currently experiencing this solar maximum, and now we have this extensive array of instruments that observe the sun in unprecedented ways. We are living in the golden era of solar multimessenger astronomy.”