Jan. 29, 2024: Energetic protons from the sun are striking the top of Earth’s atmosphere today following a strong solar flare during the early hours of Jan. 29th. This is called a “radiation storm,” and it is currently a category S2 event. Such a storm can cause elevated levels of radiation in airplanes flying over Earth’s poles and unwanted glitches in the electronics of Earth-orbiting satellites.

NASA’s Solar Dynamics Observatory recorded the M6.8-class solar flare, which started this storm:

The source of the flare was departing sunspot AR3559. Not all flares cause radiation storms, but this one did because the sunspot is unusually well connected to Earth.

That may seem counterintuitive, because the sunspot is not directly facing our planet. However, when sunspots are near the sun’s western limb (as AR3559 is), they can link to Earth magnetically. Take a look at this diagram, and you’ll understand why. It’s called “the Parker Spiral.” Protons accelerated by the flare are now following the Parker Spiral toward Earth and raining down on our atmosphere.

NOAA’s GOES-18 satellite is recording the protons as they pass by en route to Earth:

The three colors represent different energy ranges. Blue and green are especially noteworthy; they trace the most energetic protons capable of penetrating the metal hulls of satellites and aircraft. A significant pulse of these “hard” protons was recorded in the hours immediately after the flare.

The explosion also hurled a CME into space, shown here in a coronagraph animation from the Solar and Heliospheric Observatory (SOHO):

The many speckles in the animation are solar protons striking the spacecraft’s camera. It is a sign and side-effect of the radiation storm. A NASA model of the CME suggests it will graze Earth during the early hours of Jan. 31st. Confirmation awaits independent modeling by NOAA.

Jan. 9, 2024: (Spaceweather.com) Last month, sky watchers in Europe saw something rare and beautiful. A giant bank of polar stratospheric clouds (PSCs) escaped the Arctic Circle, and for more than a week they filled skies with rainbow color as far south as Italy. In the Italian comune of Sanfrè (latitude +45N), Pablo Javier Lucero was able to photograph the clouds at all hours of the day:

“Utterly incredible!” says Lucero. “I first saw the clouds at sunset on Dec. 22nd. After talking with a friend of mine, Jorgelina Alvarez, a meteorologist, we realized that these weren’t ordinary iridescent clouds, but rather Type II polar stratospheric clouds. My surprise was gigantic.”

Surprise is the correct reaction. Normally, Earth’s stratosphere has no clouds at all. Only when the temperature drops to a staggeringly-low -85 C can widely-spaced water molecules assemble into icy polar stratospheric clouds. With colors that rival auroras, PSCs are considered to be the most beautiful clouds on Earth.

During the outbreak, Spaceweather.com received hundreds of photos of PSCs. Curiously, they all came from Europe. Not a single cloud was sighted in North America or Asia. Why not?

Amy Butler of NOAA’s Chemical Sciences Laboratory has the answer: “The polar vortex can wobble like a top, and in December it was displaced towards Europe,” she explains. “You can see this in the figure below from Zac Lawrence’s website stratobserve.com.”

Cold air normally contained over the poles was carried by the wobbling vortex to mid-latitudes. Purple and green contours in the figure show where temperatures were cold enough for Type I and Type II PSCs, respectively.

Since the December outbreak of PSCs, which ended around Christmas, the polar stratosphere has warmed more than 30 degrees Celsius. Butler says this is probably the result of “a strong planetary wave breaking in the stratosphere.” Wave energy warmed the air and dispersed the rainbow-colored clouds.

The clouds might return. As January unfolds, the polar stratospheric vortex is still tilted toward mid-latitudes in Europe. If the stratosphere cools again, PSCs could re-appear over many populated areas. You can monitor the situation with daily temperature reports right here on Spaceweather.com.

Recommended: Amy Butler writes a great Polar Vortex Blog for NOAA. Check it out!