James' World 2

Starting on the night of January 19, 2026, planet Earth was treated to a global show that had only been seen once before in the 21st century: a spectacular auroral display that wasn’t triggered by a solar flare or by a coronal mass ejection, but instead by a completely different form of space weather known as a solar radiation storm. Whereas solar flares normally involve the ejection of plasma from the Sun’s photosphere and coronal mass ejections typically involve accelerated plasma particles from the Sun’s corona, a solar radiation storm is simply an intensification of the charged ions normally emitted by the Sun as part of the solar wind. Only, in a radiation storm, both the density and speed of the emitted particles get greatly enhanced.

We’re currently still in the peak years of our current sunspot cycle: the 11-year solar cycle that’s been tracked for centuries, where “peak years” see 100+ sunspots on the Sun while “valley years” see a largely featureless Sun. While several notable auroral displays have graced Earth in recent years, there’s only been one other severe (S4 or higher-class) solar radiation storm this century: back in 2003. Whereas most space weather events take around 3-4 days to traverse the Sun-Earth distance, the particles ejected from the Sun early on January 19, 2026 (UTC) were already triggering spectacular auroral displays less than 24 hours later. Here’s the science of how it all happened, and what dangers — and displays — such events hold in store for our world.

The solar corona, as shown here, is imaged out to 25 solar radii during the 2006 total solar eclipse. The longer the duration of a total solar eclipse, the darker the sky becomes, and the better the corona and background astronomical objects can be seen. In truth, the Sun’s atmosphere even encompasses the Earth and the entirety of the Solar System. The solar wind, as well as many other Sun-driven features, extend out beyond the orbit of Pluto.

The first thing you should understand — and not only people, but even most physicists, don’t fully appreciate this — is that the Earth, and all of the planets in the Solar System, are actually inside the atmosphere of the Sun. We usually think about the Sun as being a ball of plasma with a wispy, extended atmosphere and a halo-like corona surrounding it, but those are only the locations where the plasma density is the greatest. In reality, the Sun is a powerful enough, hot enough engine that it fills everything inside our heliosphere, which extends out to beyond the orbits of Neptune and Pluto, with that hot, ionized plasma.

While we typically only view the extended atmosphere of the Sun under favorable viewing conditions, like during a total solar eclipse from Earth, or from up in space with the advent of a Sun-blocking coronagraph, we’ve been able to track a wide variety of its effects. We know that it produces light, sure, but it also consistently produces a stream of ions, mostly protons but also electrons, heavier atomic nuclei, and even small amounts of antimatter, known as the solar wind. That solar wind is guided by the Sun’s magnetic field, which is driven by internal processes inside the Sun, and particularly energetic outbursts come when magnetic field lines “snap” and reconnect at, near, just outside, or even fully inside the Sun’s photosphere.

Solar coronal loops, such as those observed by NASA’s Solar Dynamics Observatory (SDO) satellite here in 2014, follow the path of the magnetic field on the Sun. When these loops ‘break’ in just the right way, they can emit coronal mass ejections, which have the potential to impact Earth. The connection between the solar corona just above the photosphere and the outer phenomena that pervade the rest of the Solar System relies on spacecraft throughout the Solar System, with the Stereo A and B spacecraft, the Parker Solar Probe, and an array of Sun-facing spacecraft located at the L1 Lagrange point (between the Earth and Sun) playing roles of paramount importance.

When those magnetic reconnection events occur internally, normally where sunspots are located, a solar flare often results. When those reconnection events occur externally, fully outside of the Sun’s photosphere, a coronal mass ejection often results. But when those reconnection events occur outside the surface but before you reach the corona, it typically just rapidly accelerates the charged particles that exist in that region outside of the photosphere. That creates the conditions for what’s known as a solar radiation storm, which can then be accompanied — usually afterwards — by either a solar flare (if the reconnection propagates backwards to the Sun’s interior) or a coronal mass ejection (if the reconnection propagates forwards to the Sun’s corona).

The 2003 event, known as the Halloween solar storms because they peaked from mid-October to early November, included both solar flares and coronal mass ejections, including the strongest solar flare ever recorded by the GOES (Geostationary Operational Environmental Satellite) system, and that was the last severe solar radiation storm that affected the Earth. On January 19, 2026, another one occurred, and it indeed was also followed up by an X-class solar flare and a coronal mass ejection. However, solar flares and coronal mass ejections are common; what was highly uncommon was the solar radiation storm, and the ultra-fast (and large flux of) solar wind particles that came towards Earth.