From Spaceweather.com

By DR.TONY PHILLIPS

May 15, 2023: Europeans are still trying to wrap their minds around what happened on April 23, 2023. Everyone knew that a CME was coming, so its impact was not a surprise. Photographers were already outside at sunset waiting for auroras. And, indeed, auroras appeared, but they were very strange.

“I had never seen anything quite like it,” says longtime aurora watcher Heiko Ulbricht of Saxony, Germany. “The auroras began to tear themselves apart, forming individual spots and blobs which rose all the way to the zenith.” Here is a sample of what he saw:

“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.

“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. Earth is the only rocky planet in our Solar System that has one.

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 tend to push the protons toward the dusk 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 often accompanied by deep red arcs of light (SARs), which are caused by heat leaking from the ring current system. These arcs were also seen on April 23rd.

Let the proton rain begin!